Publications by category
Journal articles
Goetz KT, Dinniman MS, Hückstädt LA, Robinson PW, Shero MR, Burns JM, Hofmann EE, Stammerjohn SE, Hazen EL, Ainley DG, et al (2023). Seasonal habitat preference and foraging behaviour of post-moult Weddell seals in the western Ross Sea. Royal Society Open Science, 10(1).
Borras-Chavez R, Goebel ME, Villegas-Amtmann S, Huckstadt LA, Rivera-Rebella C, Costa DP, Farina JM, Bozinovic F (2023). Time and behavioral adjustments to lactation: Insights from a marine predator.
MARINE MAMMAL SCIENCE,
39(1), 131-150.
Author URL.
Conners MG, Sisson NB, Agamboue PD, Atkinson PW, Baylis AMM, Benson SR, Block BA, Bograd SJ, Bordino P, Bowen WD, et al (2022). Mismatches in scale between highly mobile marine megafauna and marine protected areas. Frontiers in Marine Science, 9
Reisinger RR, Brooks CM, Raymond B, Freer JJ, Cotté C, Xavier JC, Trathan PN, Bornemann H, Charrassin J-B, Costa DP, et al (2022). Predator-derived bioregions in the Southern Ocean: Characteristics, drivers and representation in marine protected areas. Biological Conservation, 272
Noh HJ, Turner-Maier J, Schulberg SA, Fitzgerald ML, Johnson J, Allen KN, Hückstädt LA, Batten AJ, Alfoldi J, Costa DP, et al (2022). The Antarctic Weddell seal genome reveals evidence of selection on cardiovascular phenotype and lipid handling. Communications Biology, 5(1).
Adachi T, Naito Y, Robinson PW, Costa DP, Hückstädt LA, Holser RR, Iwasaki W, Takahashi A (2022). Whiskers as hydrodynamic prey sensors in foraging seals. Proceedings of the National Academy of Sciences of the United States of America, 119(25).
Pearson A, Schmitt T, Robeck T, Hückstädt L, Tift M (2021). First Report of Red Blood Cell Lifespan in a Marine Mammal: an Insight into Endogenous Carbon Monoxide (CO) Production. The FASEB Journal, 35(S1).
Adachi T, Takahashi A, Costa DP, Robinson PW, Hückstädt LA, Peterson SH, Holser RR, Beltran RS, Keates TR, Naito Y, et al (2021). Forced into an ecological corner: Round-the-clock deep foraging on small prey by elephant seals.
Science advances,
7(20).
Abstract:
Forced into an ecological corner: Round-the-clock deep foraging on small prey by elephant seals.
Small mesopelagic fishes dominate the world's total fish biomass, yet their ecological importance as prey for large marine animals is poorly understood. To reveal the little-known ecosystem dynamics, we identified prey, measured feeding events, and quantified the daily energy balance of 48 deep-diving elephant seals throughout their oceanic migrations by leveraging innovative technologies: animal-borne smart accelerometers and video cameras. Seals only attained positive energy balance after feeding 1000 to 2000 times per day on small fishes, which required continuous deep diving (80 to 100% of each day). Interspecies allometry suggests that female elephant seals have exceptional diving abilities relative to their body size, enabling them to exploit a unique foraging niche on small but abundant mesopelagic fish. This unique foraging niche requires extreme round-the-clock deep diving, limiting the behavioral plasticity of elephant seals to a changing mesopelagic ecosystem.
Abstract.
Blakeway J-A, Arnould JPY, Hoskins AJ, Martin-Cabrera P, Sutton GJ, Huckstadt LA, Costa DP, Páez-Rosas D, Villegas-Amtmann S (2021). Influence of hunting strategy on foraging efficiency in Galapagos sea lions. PeerJ, 9
Huckstadt LA, Pinones A, Palacios DM, McDonald BI, Dinniman MS, Hofmann EE, Burns JM, Crocker DE, Costa DP (2021). Projected shifts in the foraging habitat of crabeater seals along the Antarctic Peninsula (vol 10, pg 472, 2020).
NATURE CLIMATE CHANGE,
11(6), 551-551.
Author URL.
Huckstadt LA, Schwarz LK, Friedlaender AS, Mate BR, Zerbini AN, Kennedy A, Robbins J, Gales NJ, Costa DP (2020). A dynamic approach to estimate the probability of exposure of marine predators to oil exploration seismic surveys over continental shelf waters.
ENDANGERED SPECIES RESEARCH,
42, 185-199.
Author URL.
Yoshino K, Takahashi A, Adachi T, Costa DP, Robinson PW, Peterson SH, Hückstädt LA, Holser RR, Naito Y (2020). Acceleration-triggered animal-borne videos show a dominance of fish in the diet of female northern elephant seals.
The Journal of experimental biology,
223(Pt 5).
Abstract:
Acceleration-triggered animal-borne videos show a dominance of fish in the diet of female northern elephant seals.
Knowledge of the diet of marine mammals is fundamental to understanding their role in marine ecosystems and response to environmental change. Recently, animal-borne video cameras have revealed the diet of marine mammals that make short foraging trips. However, novel approaches that allocate video time to target prey capture events is required to obtain diet information for species that make long foraging trips over great distances. We combined satellite telemetry and depth recorders with newly developed date-/time-, depth- and acceleration-triggered animal-borne video cameras to examine the diet of female northern elephant seals during their foraging migrations across the eastern North Pacific. We obtained 48.2
h of underwater video, from cameras mounted on the head (n=12) and jaw (n=3) of seals. Fish dominated the diet (78% of 697 prey items recorded) across all foraging locations (range: 37-55°N, 122-152°W), diving depths (range: 238-1167
m) and water temperatures (range: 3.2-7.4°C), while squid comprised only 7% of the diet. Identified prey included fish such as myctophids, Merluccius sp. and Icosteus aenigmaticus, and squid such as Histioteuthis sp. Octopoteuthis sp. and Taningia danae Our results corroborate fatty acid analysis, which also found that fish are more important in the diet, and are in contrast to stomach content analyses that found cephalopods to be the most important component of the diet. Our work shows that in situ video observation is a useful method for studying the at-sea diet of long-ranging marine predators.
Abstract.
Wright TJ, Davis RW, Holser RR, Hückstädt LA, Danesi CP, Porter C, Widen SG, Williams TM, Costa DP, Sheffield-Moore M, et al (2020). Changes in Northern Elephant Seal Skeletal Muscle Following Thirty Days of Fasting and Reduced Activity. Frontiers in Physiology, 11
Keates TR, Kudela RM, Holser RR, Huckstadt LA, Simmons SE, Costa DP (2020). Chlorophyll fluorescence as measured in situ by animal-borne instruments in the northeastern Pacific Ocean.
JOURNAL OF MARINE SYSTEMS,
203 Author URL.
Hückstädt LA, Piñones A, Palacios DM, McDonald BI, Dinniman MS, Hofmann EE, Burns JM, Crocker DE, Costa DP (2020). Projected shifts in the foraging habitat of crabeater seals along the Antarctic Peninsula. Nature Climate Change, 10(5), 472-477.
Huckstadt LA, Pinones A, Palacios DM, McDonald BI, Dinniman MS, Hofmann EE, Burns JM, Crocker DE, Costa DP (2020). Projected shifts in the foraging habitat of crabeater seals along the Antarctic Peninsula (vol 56, pg 213, 2020).
NATURE CLIMATE CHANGE,
10(8), 791-791.
Author URL.
McDonald BI, Tift MS, Hückstädt LA, Jeffko M, Ponganis PJ (2020). Stroke effort and relative lung volume influence heart rate in diving sea lions.
The Journal of experimental biology,
223(Pt 5).
Abstract:
Stroke effort and relative lung volume influence heart rate in diving sea lions.
The dive response, bradycardia (decreased heart rate) and peripheral vasoconstriction, is the key mechanism allowing breath-hold divers to perform long-duration dives while actively swimming and hunting prey. This response is variable and modulated by factors such as dive duration, depth, exercise and cognitive control. This study assessed the potential role of exercise and relative lung volume in the regulation of heart rate (fH) during dives of adult female California sea lions instrumented with electrocardiogram (ECG), depth and tri-axial acceleration data loggers. A positive relationship between activity (minimum specific acceleration) and fH throughout dives suggested increased muscle perfusion associated with exercise. However, apart from late ascent, fH during dives was still less than or equal to resting fH (on land). In addition, the activity-fH relationship was weaker in long, deep dives consistent with prioritization of blood oxygen conservation over blood oxygen delivery to muscle in those dives. Pulmonary stretch receptor reflexes may also contribute to fH regulation as fH profiles generally paralleled changes in relative lung volume, especially in shallower dives and during early descent and late ascent of deeper dives. Overall, these findings support the concept that both exercise and pulmonary stretch receptor reflexes may influence the dive response in sea lions.
Abstract.
Ropert-Coudert Y, Van de Putte AP, Reisinger RR, Bornemann H, Charrassin J-B, Costa DP, Danis B, Hückstädt LA, Jonsen ID, Lea M-A, et al (2020). The retrospective analysis of Antarctic tracking data project.
Scientific data,
7(1).
Abstract:
The retrospective analysis of Antarctic tracking data project.
The Retrospective Analysis of Antarctic Tracking Data (RAATD) is a Scientific Committee for Antarctic Research project led jointly by the Expert Groups on Birds and Marine Mammals and Antarctic Biodiversity Informatics, and endorsed by the Commission for the Conservation of Antarctic Marine Living Resources. RAATD consolidated tracking data for multiple species of Antarctic meso- and top-predators to identify Areas of Ecological Significance. These datasets and accompanying syntheses provide a greater understanding of fundamental ecosystem processes in the Southern Ocean, support modelling of predator distributions under future climate scenarios and create inputs that can be incorporated into decision making processes by management authorities. In this data paper, we present the compiled tracking data from research groups that have worked in the Antarctic since the 1990s. The data are publicly available through biodiversity.aq and the Ocean Biogeographic Information System. The archive includes tracking data from over 70 contributors across 12 national Antarctic programs, and includes data from 17 predator species, 4060 individual animals, and over 2.9 million observed locations.
Abstract.
Hindell MA, Reisinger RR, Ropert-Coudert Y, Hückstädt LA, Trathan PN, Bornemann H, Charrassin J-B, Chown SL, Costa DP, Danis B, et al (2020). Tracking of marine predators to protect Southern Ocean ecosystems.
Nature,
580(7801), 87-92.
Abstract:
Tracking of marine predators to protect Southern Ocean ecosystems.
Southern Ocean ecosystems are under pressure from resource exploitation and climate change1,2. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally important region and assess current threats and protection levels. Integration of more than 4,000 tracks from 17 bird and mammal species reveals AESs around sub-Antarctic islands in the Atlantic and Indian Oceans and over the Antarctic continental shelf. Fishing pressure is disproportionately concentrated inside AESs, and climate change over the next century is predicted to impose pressure on these areas, particularly around the Antarctic continent. At present, 7.1% of the ocean south of 40°S is under formal protection, including 29% of the total AESs. The establishment and regular revision of networks of protection that encompass AESs are needed to provide long-term mitigation of growing pressures on Southern Ocean ecosystems.
Abstract.
Harcourt R, Sequeira AMM, Zhang X, Roquet F, Komatsu K, Heupel M, McMahon C, Whoriskey F, Meekan M, Carroll G, et al (2019). Animal-Borne Telemetry: an Integral Component of the Ocean Observing Toolkit.
FRONTIERS IN MARINE SCIENCE,
6 Author URL.
Horning M, Andrews RD, Bishop AM, Boveng PL, Costa DP, Crocker DE, Haulena M, Hindell M, Hindle AG, Holser RR, et al (2019). Best practice recommendations for the use of external telemetry devices on pinnipeds. Animal Biotelemetry, 7(1).
Adachi T, Huckstadt LA, Tift MS, Costa DP, Naito Y, Takahashi A (2019). Inferring prey size variation from mandible acceleration in northern elephant seals.
MARINE MAMMAL SCIENCE,
35(3), 893-908.
Author URL.
Hindle AG, Allen KN, Batten AJ, Hückstädt LA, Turner-Maier J, Schulberg SA, Johnson J, Karlsson E, Lindblad-Toh K, Costa DP, et al (2019). Low guanylyl cyclase activity in Weddell seals: implications for peripheral vasoconstriction and perfusion of the brain during diving. AJP Regulatory Integrative and Comparative Physiology, 316(6), r704-r715.
Brault EK, Koch PL, Costa DP, McCarthy MD, Huckstadt LA, Goetz KT, McMahon KW, Goebel ME, Karlsson O, Teilmann J, et al (2019). Trophic position and foraging ecology of Ross, Weddell, and crabeater seals revealed by compound-specific isotope analysis.
MARINE ECOLOGY PROGRESS SERIES,
611, 1-18.
Author URL.
Keates TR, Kudela RM, Holser RR, Hückstädt LA, Simmons SE, Costa DP (2019). WITHDRAWN: Chlorophyll fluorescence as measured in situ by animal-borne instruments in the northeastern Pacific Ocean. Journal of Marine Systems
Tift MS, Hückstädt LA, Ponganis PJ (2018). Anterior vena caval oxygen profiles in a deep-diving California sea lion: arteriovenous shunts, a central venous oxygen store and oxygenation during lung collapse.
The Journal of experimental biology,
221(Pt 1).
Abstract:
Anterior vena caval oxygen profiles in a deep-diving California sea lion: arteriovenous shunts, a central venous oxygen store and oxygenation during lung collapse.
Deep-diving California sea lions (Zalophus californianus) can maintain arterial hemoglobin saturation (SO2 ) above 90% despite lung collapse (lack of gas exchange) and extremely low posterior vena caval SO2 in the middle of the dive. We investigated anterior vena caval PO2 and SO2 during dives of an adult female sea lion to investigate two hypotheses: (1) posterior vena caval SO2 is not representative of the entire venous oxygen store and (2) a well-oxygenated (arterialized) central venous oxygen reservoir might account for maintenance of arterial SO2 during lung collapse. During deep dives, initial anterior vena caval SO2 was elevated at 83.6±8.4% (n=102), presumably owing to arteriovenous shunting. It remained high until the bottom phase of the dive and then decreased during ascent, whereas previously determined posterior vena caval SO2 declined during descent and then often increased during ascent. These divergent patterns confirmed that posterior vena caval SO2 was not representative of the entire venous oxygen store. Prior to and early during descent of deep dives, the high SO2 values of both the anterior and posterior venae cavae may enhance arterialization of a central venous oxygen store. However, anterior vena caval SO2 values at depths beyond lung collapse reached levels as low as 40%, making it unlikely that even a completely arterialized central venous oxygen store could account for maintenance of high arterial SO2 These findings suggest that maintenance of high arterial SO2 during deep dives is due to persistence of some gas exchange at depths beyond presumed lung collapse.
Abstract.
Sequeira AMM, Rodríguez JP, Eguíluz VM, Harcourt R, Hindell M, Sims DW, Duarte CM, Costa DP, Fernández-Gracia J, Ferreira LC, et al (2018). Convergence of marine megafauna movement patterns in coastal and open oceans.
Proc Natl Acad Sci U S A,
115(12), 3072-3077.
Abstract:
Convergence of marine megafauna movement patterns in coastal and open oceans.
The extent of increasing anthropogenic impacts on large marine vertebrates partly depends on the animals' movement patterns. Effective conservation requires identification of the key drivers of movement including intrinsic properties and extrinsic constraints associated with the dynamic nature of the environments the animals inhabit. However, the relative importance of intrinsic versus extrinsic factors remains elusive. We analyze a global dataset of ∼2.8 million locations from >2,600 tracked individuals across 50 marine vertebrates evolutionarily separated by millions of years and using different locomotion modes (fly, swim, walk/paddle). Strikingly, movement patterns show a remarkable convergence, being strongly conserved across species and independent of body length and mass, despite these traits ranging over 10 orders of magnitude among the species studied. This represents a fundamental difference between marine and terrestrial vertebrates not previously identified, likely linked to the reduced costs of locomotion in water. Movement patterns were primarily explained by the interaction between species-specific traits and the habitat(s) they move through, resulting in complex movement patterns when moving close to coasts compared with more predictable patterns when moving in open oceans. This distinct difference may be associated with greater complexity within coastal microhabitats, highlighting a critical role of preferred habitat in shaping marine vertebrate global movements. Efforts to develop understanding of the characteristics of vertebrate movement should consider the habitat(s) through which they move to identify how movement patterns will alter with forecasted severe ocean changes, such as reduced Arctic sea ice cover, sea level rise, and declining oxygen content.
Abstract.
Author URL.
Bagchi A, Batten AJ, Levin M, Allen KN, Fitzgerald ML, Hückstädt LA, Costa DP, Buys ES, Hindle AG (2018). Intrinsic anti-inflammatory properties in the serum of two species of deep-diving seal.
The Journal of experimental biology,
221(Pt 13).
Abstract:
Intrinsic anti-inflammatory properties in the serum of two species of deep-diving seal.
Weddell and elephant seals are deep-diving mammals, which rely on lung collapse to limit nitrogen absorption and prevent decompression injury. Repeated collapse and re-expansion exposes the lungs to multiple stressors, including ischemia-reperfusion, alveolar shear stress and inflammation. There is no evidence, however, that diving damages pulmonary function in these species. To investigate potential protective strategies in deep-diving seals, we examined the inflammatory response of seal whole blood exposed to lipopolysaccharide (LPS), a potent endotoxin. Interleukin-6 (IL6) cytokine production elicited by LPS exposure was 50 to 500 times lower in blood of healthy northern elephant seals and Weddell seals compared with that of healthy human blood. In contrast to the ∼6× increased production of IL6 protein from LPS-exposed Weddell seal whole blood, isolated Weddell seal peripheral blood mononuclear cells, under standard cell culture conditions using medium supplemented with fetal bovine serum (FBS), produced a robust LPS response (∼300×). Induction of Il6 mRNA expression as well as production of IL6, IL8, IL10, KC-like and TNFα were reduced by substituting FBS with an equivalent amount of autologous seal serum. Weddell seal serum also attenuated the inflammatory response of RAW 267.4 mouse macrophage cells exposed to LPS. Cortisol level and the addition of serum lipids did not impact the cytokine response in cultured cells. These data suggest that seal serum possesses anti-inflammatory properties, which may protect deep divers from naturally occurring inflammatory challenges such as dive-induced hypoxia-reoxygenation and lung collapse.
Abstract.
Hindle AG, Bagchi A, Batten A, Levin M, Allen KN, Huckstadt LA, Costa DP, Zapol WM, Buys ES (2018). Intrinsic anti‐inflammatory properties of serum in deep‐diving seals. The FASEB Journal, 32(S1), 859.9-859.9.
Kooyman GL, van Dam RP, Hückstädt LA (2018). Night diving by some emperor penguins during the winter breeding period at Cape Washington.
The Journal of experimental biology,
221(Pt 1).
Abstract:
Night diving by some emperor penguins during the winter breeding period at Cape Washington.
All through the bird literature and feature films, there is much ado about dedicated emperor penguin males fasting for 115
days while they do all the incubation of the single egg. Sometimes, they may not fast for so long. Based on a winter visit to Cape Washington, we obtained evidence that some birds may feed before the egg is laid, and if they do, and some are males, then their fast is much less than 115
days. The consequence of a shorter fast for the male is a better chance of completing the 65 day incubation fast and success in fledging the chick. For those in northern colonies that may migrate south, there will be closer access to open water, but there will be the need to dive in the dark.
Abstract.
McHuron EA, Peterson SH, Hückstädt LA, Melin SR, Harris JD, Costa DP (2018). The energetic consequences of behavioral variation in a marine carnivore.
Ecology and evolution,
8(8), 4340-4351.
Abstract:
The energetic consequences of behavioral variation in a marine carnivore.
Intraspecific variability in foraging behavior has been documented across a range of taxonomic groups, yet the energetic consequences of this variation are not well understood for many species. Understanding the effect of behavioral variation on energy expenditure and acquisition is particularly crucial for mammalian carnivores because they have high energy requirements that place considerable pressure on prey populations. To determine the influence of behavior on energy expenditure and balance, we combined simultaneous measurements of at-sea field metabolic rate (FMR) and foraging behavior in a marine carnivore that exhibits intraspecific behavioral variation, the California sea lion (Zalophus californianus). Sea lions exhibited variability in at-sea FMR, with some individuals expending energy at a maximum of twice the rate of others. This variation was in part attributable to differences in diving behavior that may have been reflective of diet; however, this was only true for sea lions using a foraging strategy consisting of epipelagic (
Abstract.
Hückstädt LA, Holser RR, Tift MS, Costa DP (2018). The extra burden of motherhood: reduced dive duration associated with pregnancy status in a deep-diving mammal, the northern elephant seal.
Biology letters,
14(2).
Abstract:
The extra burden of motherhood: reduced dive duration associated with pregnancy status in a deep-diving mammal, the northern elephant seal.
The cost of pregnancy is hard to study in marine mammals, particularly in species that undergo pregnancy while diving continuously at sea such as elephant seals (genus Mirounga). We analysed the diving behaviour of confirmed pregnant and non-pregnant northern elephant seals (M. angustirostris, n = 172) and showed that after an initial continuous increase in dive duration, dives of pregnant females become shorter after week 17. The reasons for this reduction in dive duration remain unknown, but we hypothesize that increased fetal demand for oxygen could be the cause. Our findings reveal an opportunity to explore the use of biologging data to investigate pregnancy status of free-ranging marine mammals and factors that could affect pregnancy success.
Abstract.
Pirotta E, Mangel M, Costa DP, Mate B, Goldbogen JA, Palacios DM, Hückstädt LA, McHuron EA, Schwarz L, New L, et al (2017). A Dynamic State Model of Migratory Behavior and Physiology to Assess the Consequences of Environmental Variation and Anthropogenic Disturbance on Marine Vertebrates.
The American naturalist,
191(2), E40-E56.
Abstract:
A Dynamic State Model of Migratory Behavior and Physiology to Assess the Consequences of Environmental Variation and Anthropogenic Disturbance on Marine Vertebrates.
Integrating behavior and physiology is critical to formulating new hypotheses on the evolution of animal life-history strategies. Migratory capital breeders acquire most of the energy they need to sustain migration, gestation, and lactation before parturition. Therefore, when predicting the impact of environmental variation on such species, a mechanistic understanding of the physiology of their migratory behavior is required. Using baleen whales as a model system, we developed a dynamic state variable model that captures the interplay among behavioral decisions, energy, reproductive needs, and the environment. We applied the framework to blue whales (Balaenoptera musculus) in the eastern North Pacific Ocean and explored the effects of environmental and anthropogenic perturbations on female reproductive success. We demonstrate the emergence of migration to track prey resources, enabling us to quantify the trade-offs among capital breeding, body condition, and metabolic expenses. We predict that periodic climatic oscillations affect reproductive success less than unprecedented environmental changes do. The effect of localized, acute anthropogenic impacts depended on whales' behavioral response to the disturbance; chronic, but weaker, disturbances had little effect on reproductive success. Because we link behavior and vital rates by modeling individuals' energetic budgets, we provide a general framework to investigate the ecology of migration and assess the population consequences of disturbance, while identifying critical knowledge gaps.
Abstract.
Tift MS, Hückstädt LA, McDonald BI, Thorson PH, Ponganis PJ (2017). Flipper stroke rate and venous oxygen levels in free-ranging California sea lions.
The Journal of experimental biology,
220(Pt 8), 1533-1540.
Abstract:
Flipper stroke rate and venous oxygen levels in free-ranging California sea lions.
The depletion rate of the blood oxygen store, development of hypoxemia and dive capacity are dependent on the distribution and rate of blood oxygen delivery to tissues while diving. Although blood oxygen extraction by working muscle would increase the blood oxygen depletion rate in a swimming animal, there is little information on the relationship between muscle workload and blood oxygen depletion during dives. Therefore, we examined flipper stroke rate, a proxy of muscle workload, and posterior vena cava oxygen profiles in four adult female California sea lions (Zalophus californianus) during foraging trips at sea. Flipper stroke rate analysis revealed that sea lions minimized muscle metabolism with a stroke-glide strategy when diving, and exhibited prolonged glides during the descent of deeper dives (>100
m). During the descent phase of these deep dives, 55±21% of descent was spent gliding, with the longest glides lasting over 160
s and covering a vertical distance of 340
m. Animals also consistently glided to the surface from 15 to 25
m depth during these deeper dives. Venous hemoglobin saturation (SO2 ) profiles were highly variable throughout dives, with values occasionally increasing during shallow dives. The relationship between SO2 and flipper stroke rate was weak during deeper dives, while this relationship was stronger during shallow dives. We conclude that (1) the depletion of oxygen in the posterior vena cava in deep-diving sea lions is not dependent on stroke effort, and (2) stroke-glide patterns during dives contribute to a reduction of muscle metabolic rate.
Abstract.
Roquet F, Boehme L, Block B, Charrassin J-B, Costa D, Guinet C, Harcourt RG, Hindell MA, Huckstadt LA, McMahon CR, et al (2017). Ocean Observations Using Tagged Animals.
OCEANOGRAPHY,
30(2), 139-139.
Author URL.
Hückstädt LA, McCarthy MD, Koch PL, Costa DP (2017). What difference does a century make? Shifts in the ecosystem structure of the Ross Sea, Antarctica, as evidenced from a sentinel species, the Weddell seal.
Proceedings. Biological sciences,
284(1861).
Abstract:
What difference does a century make? Shifts in the ecosystem structure of the Ross Sea, Antarctica, as evidenced from a sentinel species, the Weddell seal.
The arrival of humans to Antarctica's Ross Sea (100+ years ago) led to a slow, but sustained increase in human activities in the area. To investigate if human presence has influenced the structure of the ecosystem over the last century, we compared historical (ca 100 years old) and modern samples of a sentinel species, the Weddell seal (Leptonychotes weddellii), using both bulk tissue and compound-specific stable isotope analysis. The historical isotopic niche of Weddell seals was over five times larger than the modern niche. The isotopic values of individual amino acids showed a clear segregation between historical and modern samples, indicative of differences at the base of the trophic web. Further, we found no significant differences in the trophic position of Weddell seals between the two periods. Our study revealed that the Ross Sea has undergone detectable changes (i.e. in the primary producers community) in the last century, but the presence of humans has not disrupted trophic interactions supporting Weddell seals.
Abstract.
Fiechter J, Huckstadt LA, Rose KA, Costa DP (2016). A fully coupled ecosystem model to predict the foraging ecology of apex predators in the California Current.
MARINE ECOLOGY PROGRESS SERIES,
556, 273-285.
Author URL.
Fregosi S, Klinck H, Horning M, Costa DP, Mann D, Sexton K, Hückstädt LA, Mellinger DK, Southall BL (2016). An animal-borne active acoustic tag for minimally invasive behavioral response studies on marine mammals. Animal Biotelemetry, 4(1).
Hindell MA, McMahon CR, Bester MN, Boehme L, Costa D, Fedak MA, Guinet C, Herraiz-Borreguero L, Harcourt RG, Huckstadt L, et al (2016). Circumpolar habitat use in the southern elephant seal: implications for foraging success and population trajectories.
ECOSPHERE,
7(5).
Author URL.
Riet-Sapriza FG, Costa DP, Franco-Trecu V, Marin Y, Chocca J, Gonzalez B, Beathyate G, Chilvers BL, Huckstadt LA (2016). Foraging behavior of lactating South American sea lions (<i>Otaria flavescens</i>) and spatial-temporal resource overlap with the Uruguayan fisheries (vol 88, pg 106, 2013).
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY,
132, 267-268.
Author URL.
Hückstädt LA, Tift MS, Riet-Sapriza F, Franco-Trecu V, Baylis AMM, Orben RA, Arnould JPY, Sepulveda M, Santos-Carvallo M, Burns JM, et al (2016). Regional variability in diving physiology and behavior in a widely distributed air-breathing marine predator, the South American sea lion (Otaria byronia).
The Journal of experimental biology,
219(Pt 15), 2320-2330.
Abstract:
Regional variability in diving physiology and behavior in a widely distributed air-breathing marine predator, the South American sea lion (Otaria byronia).
Our understanding of how air-breathing marine predators cope with environmental variability is limited by our inadequate knowledge of their ecological and physiological parameters. Because of their wide distribution along both coasts of the sub-continent, South American sea lions (Otaria byronia) provide a valuable opportunity to study the behavioral and physiological plasticity of a marine predator in different environments. We measured the oxygen stores and diving behavior of South American sea lions throughout most of its range, allowing us to demonstrate that diving ability and behavior vary across its range. We found no significant differences in mass-specific blood volumes of sea lions among field sites and a negative relationship between mass-specific oxygen storage and size, which suggests that exposure to different habitats and geographical locations better explains oxygen storage capacities and diving capability in South American sea lions than body size alone. The largest animals in our study (individuals from Uruguay) were the shallowest and shortest duration divers, and had the lowest mass-specific total body oxygen stores, while the deepest and longest duration divers (individuals from southern Chile) had significantly larger mass-specific oxygen stores, despite being much smaller animals. Our study suggests that the physiology of air-breathing diving predators is not fixed, but that it can be adjusted, to a certain extent, depending on the ecological setting and or habitat. These adjustments can be thought of as a 'training effect': as the animal continues to push its physiological capacity through greater hypoxic exposure, its breath-holding capacity increases.
Abstract.
Beltran RS, Peterson SH, McHuron EA, Reichmuth C, Hückstädt LA, Costa DP (2016). Seals and sea lions are what they eat, plus what? Determination of trophic discrimination factors for seven pinniped species.
Rapid communications in mass spectrometry : RCM,
30(9), 1115-1122.
Abstract:
Seals and sea lions are what they eat, plus what? Determination of trophic discrimination factors for seven pinniped species.
RationaleMixing models are a common method for quantifying the contribution of prey sources to the diet of an individual using stable isotope analysis; however, these models rely upon a known trophic discrimination factor (hereafter, TDF) that results from fractionation between prey and animal tissues. Quantifying TDFs in captive animals is ideal, because diet is controlled and the proportional contributions and isotopic values of all prey items are known.MethodsTo calculate TDFs for the Hawaiian monk seal, northern elephant seal, bearded seal, ringed seal, spotted seal, harbor seal, and California sea lion, we obtained whiskers, serum, plasma, red blood cells, and prey items from nine captive individuals. We obtained δ(13) C and δ(15) N values using continuous-flow isotope-ratio mass spectrometry. The average δ(13) C and δ(15) N values from bulk and lipid-corrected prey from the diet were subtracted from the δ(13) C and δ(15) N values of each blood and whisker sample to calculate tissue-specific TDFs for each individual (∆(13) C or ∆(15) N).ResultsThe ∆(13) C values ranged from +1.7 to +3.2‰ (bulk prey) and from +0.8 to +1.9‰ (lipid-corrected prey) for the various blood components, and from +3.9 to +4.6‰ (bulk prey) or +2.6 to +3.9‰ (lipid-corrected prey) for whiskers. The ∆(15) N values ranged from +2.2 to +4.3‰ for blood components and from +2.6 to +4.0‰ for whiskers. The TDFs tended to group by tissue, with whiskers having greater ∆(13) C values than blood components. In contrast, the ∆(15) N values were greater in serum and plasma than in red blood cells and whiskers.ConclusionsBy providing the first TDF values for five seal species (family Phocidae) and one otariid species (family Otariidae), our study facilitates more accurate mixing models for these species. These values are particularly important for critically endangered Hawaiian monk seals and the three Arctic seal species (bearded, ringed, and spotted) that are faced with a rapidly changing environment.
Abstract.
Schwarz LK, Villegas-Amtmann S, Beltran RS, Costa DP, Goetsch C, Hückstädt L, Maresh JL, Peterson SH (2015). Comparisons and Uncertainty in Fat and Adipose Tissue Estimation Techniques: the Northern Elephant Seal as a Case Study.
PloS one,
10(6).
Abstract:
Comparisons and Uncertainty in Fat and Adipose Tissue Estimation Techniques: the Northern Elephant Seal as a Case Study.
Fat mass and body condition are important metrics in bioenergetics and physiological studies. They can also link foraging success with demographic rates, making them key components of models that predict population-level outcomes of environmental change. Therefore, it is important to incorporate uncertainty in physiological indicators if results will lead to species management decisions. Maternal fat mass in elephant seals (Mirounga spp) can predict reproductive rate and pup survival, but no one has quantified or identified the sources of uncertainty for the two fat mass estimation techniques (labeled-water and truncated cones). The current cones method can provide estimates of proportion adipose tissue in adult females and proportion fat of juveniles in northern elephant seals (M. angustirostris) comparable to labeled-water methods, but it does not work for all cases or species. We reviewed components and assumptions of the technique via measurements of seven early-molt and seven late-molt adult females. We show that seals are elliptical on land, rather than the assumed circular shape, and skin may account for a high proportion of what is often defined as blubber. Also, blubber extends past the neck-to-pelvis region, and comparisons of new and old ultrasound instrumentation indicate previous measurements of sculp thickness may be biased low. Accounting for such differences, and incorporating new measurements of blubber density and proportion of fat in blubber, we propose a modified cones method that can isolate blubber from non-blubber adipose tissue and separate fat into skin, blubber, and core compartments. Lastly, we found that adipose tissue and fat estimates using tritiated water may be biased high during the early molt. Both the tritiated water and modified cones methods had high, but reducible, uncertainty. The improved cones method for estimating body condition allows for more accurate quantification of the various tissue masses and may also be transferrable to other species.
Abstract.
Lawson GL, Hückstädt LA, Lavery AC, Jaffré FM, Wiebe PH, Fincke JR, Crocker DE, Costa DP (2015). Development of an animal-borne “sonar tag” for quantifying prey availability: test deployments on northern elephant seals. Animal Biotelemetry, 3(1).
Sepúlveda M, Newsome SD, Pavez G, Oliva D, Costa DP, Hückstädt LA (2015). Using Satellite Tracking and Isotopic Information to Characterize the Impact of South American Sea Lions on Salmonid Aquaculture in Southern Chile.
PloS one,
10(8).
Abstract:
Using Satellite Tracking and Isotopic Information to Characterize the Impact of South American Sea Lions on Salmonid Aquaculture in Southern Chile.
Apex marine predators alter their foraging behavior in response to spatial and/or seasonal changes in natural prey distribution and abundance. However, few studies have identified the impacts of aquaculture that represents a spatially and temporally predictable and abundant resource on their foraging behavior. Using satellite telemetry and stable isotope analysis we examined the degree of spatial overlap between the South American sea lion (SASL) and salmon farms, and quantify the amount of native prey versus farmed salmonids in SASL diets. We instrumented eight SASL individuals with SRDL-GPS tags. Vibrissae, hair and skin samples were collected for δ13C and δ15N analyses from five of the tagged individuals and from four males captured in a haul-out located adjacent to salmon farms. Tracking results showed that almost all the foraging areas of SASL are within close proximity to salmon farms. The most important prey for the individuals analyzed was farmed salmonids, with an estimated median (±SD) contribution of 19.7 ± 13.5‰ and 15.3 ± 9.6‰ for hair and skin, respectively. Using vibrissae as a temporal record of diet for each individual, we observed a remarkable switch in diet composition in two SASL, from farmed salmonids to pelagic fishes, which coincided with the decrease of salmon production due to the infectious salmon anemia virus that affected salmon farms in Chile at the end of 2008. Our study demonstrates the usefulness of integrating stable isotope derived dietary data with movement patterns to characterize the impacts of a non-native prey on the foraging ecology of an apex marine predator, providing important applied implications in situations where interactions between aquaculture and wildlife are common.
Abstract.
Hueckstaedt LA, Quinones RA, Sepulveda M, Costa DP (2014). Movement and diving patterns of juvenile male South American sea lions off the coast of central Chile.
MARINE MAMMAL SCIENCE,
30(3), 1175-1183.
Author URL.
Roquet F, Wunsch C, Forget G, Heimbach P, Guinet C, Reverdin G, Charrassin J-B, Bailleul F, Costa DP, Huckstadt LA, et al (2013). Estimates of the Southern Ocean general circulation improved by animal-borne instruments.
GEOPHYSICAL RESEARCH LETTERS,
40(23), 6176-6180.
Author URL.
Riet-Sapriza FG, Costa DP, Franco-Trecu V, Marin Y, Chocca J, Gonzalez B, Beathyate G, Chilvers BL, Hueckstadt LA (2013). Foraging behavior of lactating South American sea lions (<i>Otaria flavescens</i>) and spatial-temporal resource overlap with the Uruguayan fisheries.
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY,
88-89, 106-119.
Author URL.
Fregosi S, Klinck H, Horning M, Mellinger DK, Costa DP, Mann DA, Sexton K, Huckstadt L (2013). Use of an animal-borne active acoustic tag to conduct minimally-invasive behavioral response studies.
The Journal of the Acoustical Society of America,
134(5_Supplement), 4044-4044.
Abstract:
Use of an animal-borne active acoustic tag to conduct minimally-invasive behavioral response studies
A pilot study was conducted to evaluate the potential of animal-borne active and passive acoustic tags for conducting minimally-invasive behavioral response studies on pinnipeds. A prototype tag was developed and tested on juvenile northern elephant seals (Mirounga angustirostris) using translocation experiments at Año Nuevo State Park, CA, USA, in spring 2012. The principal scientific questions of this pilot study were (1) do low-intensity sounds emitted by an animal-borne tag elicit behavioral responses, and (2) are potential animal responses related to signal content (e.g. threatening vs non-threatening)? Preliminary results indicate that (1) low-intensity sounds emitted by animal-borne tags elicit distinct behavioral responses, (2) these responses appear related to signal content, and (3) the responses may differ based on depth, bathymetry, and location. The results of the study show the promise of this approach as a minimally invasive and cost-effective method to investigate animal responses to underwater sounds, as well as a method to develop mitigation strategies. We are currently in the process of improving the tag design for future field efforts with the goal to increase the sample size, range of acoustic stimuli, and age/sex classes of tagged seals. [Funding from NOAA/NMFS Ocean Acoustics Program.]
Abstract.
Klinck H, Horning M, Mellinger DK, Costa DP, Fregosi S, Mann DA, Sexton K, Huckstadt L (2012). Animal-borne active acoustic tags: a new paradigm to conduct minimally invasive behavioral response studies?.
The Journal of the Acoustical Society of America,
132(3_Supplement), 2009-2009.
Abstract:
Animal-borne active acoustic tags: a new paradigm to conduct minimally invasive behavioral response studies?
In 2011 a pilot study was begun to evaluate the potential of animal-borne active acoustic tags for conducting minimally-invasive behavioral response studies on pinnipeds. A basic prototype tag was developed and tested on juvenile northern elephant seals (Mirounga angustirostris) during translocation experiments at Año Nuevo State Park, CA, USA in spring 2012. The principal scientific questions of this pilot study were these: (1) do sounds emitted from an animal-borne low acoustic intensity tag elicit behavioral responses, and (2) are potential animal responses related to signal content (e.g. threatening vs. non-threatening). Although the sample size was small, preliminary results indicate that (1) low-intensity sounds emitted by animal-borne tags elicit distinct behavioral responses, (2) these responses appear related to signal content, and (3) the responses may differ based on depth, bathymetry, and location. The results of the conducted study show the promise of this approach as a minimally-invasive and cost-effective method to investigate animal responses to underwater sounds, as well as a method to develop mitigation strategies. Future efforts would increase the sample size, range of acoustic stimuli, and age/sex classes of tagged seals. [Funding from NOAA/NMFS Ocean Acoustics Program.]
Abstract.
Hueckstaedt LA, Burns JM, Koch PL, McDonald BI, Crocker DE, Costa DP (2012). Diet of a specialist in a changing environment: the crabeater seal along the western Antarctic Peninsula.
MARINE ECOLOGY PROGRESS SERIES,
455, 287-301.
Author URL.
Robinson PW, Costa DP, Crocker DE, Gallo-Reynoso JP, Champagne CD, Fowler MA, Goetsch C, Goetz KT, Hassrick JL, Hückstädt LA, et al (2012). Foraging behavior and success of a mesopelagic predator in the northeast Pacific Ocean: insights from a data-rich species, the northern elephant seal.
PloS one,
7(5).
Abstract:
Foraging behavior and success of a mesopelagic predator in the northeast Pacific Ocean: insights from a data-rich species, the northern elephant seal.
The mesopelagic zone of the northeast Pacific Ocean is an important foraging habitat for many predators, yet few studies have addressed the factors driving basin-scale predator distributions or inter-annual variability in foraging and breeding success. Understanding these processes is critical to reveal how conditions at sea cascade to population-level effects. To begin addressing these challenging questions, we collected diving, tracking, foraging success, and natality data for 297 adult female northern elephant seal migrations from 2004 to 2010. During the longer post-molting migration, individual energy gain rates were significant predictors of pregnancy. At sea, seals focused their foraging effort along a narrow band corresponding to the boundary between the sub-arctic and sub-tropical gyres. In contrast to shallow-diving predators, elephant seals target the gyre-gyre boundary throughout the year rather than follow the southward winter migration of surface features, such as the Transition Zone Chlorophyll Front. We also assessed the impact of added transit costs by studying seals at a colony near the southern extent of the species' range, 1,150 km to the south. A much larger proportion of seals foraged locally, implying plasticity in foraging strategies and possibly prey type. While these findings are derived from a single species, the results may provide insight to the foraging patterns of many other meso-pelagic predators in the northeast Pacific Ocean.
Abstract.
Padman L, Costa DP, Dinniman MS, Fricker HA, Goebel ME, Huckstadt LA, Humbert A, Joughin I, Lenaerts JTM, Ligtenberg SRM, et al (2012). Oceanic controls on the mass balance of Wilkins Ice Shelf, Antarctica.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS,
117 Author URL.
Chilvers BL, Amey JM, Huckstadt LA, Costa DP (2011). Investigating foraging utilization distribution of female New Zealand sea lions, Auckland Islands.
POLAR BIOLOGY,
34(4), 565-574.
Author URL.
Villegas-Amtmann S, Simmons SE, Kuhn CE, Huckstadt LA, Costa DP (2011). Latitudinal range influences the seasonal variation in the foraging behavior of marine top predators.
PloS one,
6(8).
Abstract:
Latitudinal range influences the seasonal variation in the foraging behavior of marine top predators.
Non-migratory resident species should be capable of modifying their foraging behavior to accommodate changes in prey abundance and availability associated with a changing environment. Populations that are better adapted to change will have higher foraging success and greater potential for survival in the face of climate change. We studied two species of resident central place foragers from temperate and equatorial regions with differing population trends and prey availability associated to season, the California sea lion (Zalophus californianus) (CSL) whose population is increasing and the endangered Galapagos sea lion (Zalophus wollebaeki) (GSL) whose population is declining. To determine their response to environmental change, we studied and compared their diving behavior using time-depth recorders and satellite location tags and their diet by measuring C and N isotope ratios during a warm and a cold season. Based on latitudinal differences in oceanographic productivity, we hypothesized that the seasonal variation in foraging behavior would differ for these two species. CSL exhibited greater seasonal variability in their foraging behavior as seen in changes to their diving behavior, foraging areas and diet between seasons. Conversely, GSL did not change their diving behavior between seasons, presenting three foraging strategies (shallow, deep and bottom divers) during both. GSL exhibited greater dive and foraging effort than CSL. We suggest that during the warm and less productive season a greater range of foraging behaviors in CSL was associated with greater competition for prey, which relaxed during the cold season when resource availability was greater. GSL foraging specialization suggests that resources are limited throughout the year due to lower primary production and lower seasonal variation in productivity compared to CSL. These latitudinal differences influence their foraging success, pup survival and population growth reflected in contrasting population trends in which CSL are more successful and potentially more resilient to climate change.
Abstract.
Hückstädt LA, Koch PL, McDonald BI, Goebel ME, Crocker DE, Costa DP (2011). Stable isotope analyses reveal individual variability in the trophic ecology of a top marine predator, the southern elephant seal.
Oecologia,
169(2), 395-406.
Abstract:
Stable isotope analyses reveal individual variability in the trophic ecology of a top marine predator, the southern elephant seal.
Identifying individuals' foraging strategies is critical to understanding the ecology of a species, and can provide the means to predict possible ecological responses to environmental change. Our study combines stable isotope analysis and satellite telemetry to study the variability in individual foraging strategies of adult female southern elephant seals (Mirounga leonina). Our hypothesis is that female elephant seals from the Western Antarctica Peninsula (WAP) display individual specialization in their diets. We captured adult female elephant seals (n = 56, 2005-2009) at Livingston Island (Antarctica), and instrumented them with SMRU-CTD satellite tags. We collected blood, fur, and vibrissae samples for δ(13)C and δ(15)N analyses. The mean values for all vibrissae were -21.0 ± 0.7‰ for δ(13)C, and 10.4 ± 0.8‰, for δ(15)N. The individual variability of δ(13)C (60%) was more important than the within-individual variability (40%) in explaining the total variance observed in our data. For δ(15)N, the results showed the opposite trend, with the within-individual variability (64%) contributing more to the total variance than the individual variability (36%), likely associated with the effect that the fasting periods have on δ(15)N values. Most individuals were specialists, as inferred from the low intra-individual variability of δ(13)C values with respect to the population variability, with half the individuals utilizing 31% or less of their available niche. We found eight different foraging strategies for these animals. Female elephant seals from the WAP are a diverse group of predators with individuals utilizing only a small portion of the total available niche, with the consequent potential to expand their foraging habits to exploit other resources or environments in the Southern Ocean.
Abstract.
Costa DP, Huckstadt LA, Crocker DE, McDonald BI, Goebel ME, Fedak MA (2010). Approaches to studying climatic change and its role on the habitat selection of antarctic pinnipeds.
Integrative and comparative biology,
50(6), 1018-1030.
Abstract:
Approaches to studying climatic change and its role on the habitat selection of antarctic pinnipeds.
Top predators integrate resources over time and space, and depending on the particular species they represent, different components of the marine environment. The habitat utilization of top predators has been studied using electronic tags to follow their movements and foraging behavior. In addition, these tags provide information on the physical characteristics of the water column (temperature and salinity) at a scale and resolution that is coincident with the animals' behavior. In addition to data on the animals' behavior, these tags provide physical oceanographic data in regions or at times they cannot be collected using other currently available technologies. These data inform us on how these important top predators are likely to respond to climatic change, as well as about how the Southern Ocean is changing.
Abstract.
Padman L, Costa DP, Bolmer ST, Goebel ME, Huckstadt LA, Jenkins A, McDonald BI, Shoosmith DR (2010). Seals map bathymetry of the Antarctic continental shelf.
GEOPHYSICAL RESEARCH LETTERS,
37 Author URL.
Huckstadt LA, Rojas CP, Antezana T (2007). Stable isotope analysis reveals pelagic foraging by the Southern sea lion in central Chile.
JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY,
347(1-2), 123-133.
Author URL.
Hückstädt LA (2005). Nuevos registros de cetAceos para la VIII RegiOn, Chile (1997 a 1999). Gayana (Concepción), 69(2).
Hückstädt LA, Antezana T (2004). Behaviour of Southern sea lions in presence of killer whales during fishing operations in Central Chile.
SCIENTIA MARINA,
68(2), 295-298.
Author URL.
Hückstädt LA, Krautz MC (2004). Interaction between southern sea lions <i>Otaria flavescens</i> and jack mackerel <i>Trachurus symmetricus</i> commercial fishery off Central Chile:: a geostatistical approach.
MARINE ECOLOGY PROGRESS SERIES,
282, 285-294.
Author URL.
Hückstädt LA, Antezana T (2003). Behaviour of the southern sea lion (<i>Otaria flavescens</i>) and consumption of the catch during purse-seining for jack mackerel (<i>Trachurus symmetricus</i>) off central Chile.
ICES JOURNAL OF MARINE SCIENCE,
60(5), 1003-1011.
Author URL.
Hückstädt L, Antezana T (2001). An observation of parturition in a stranded <i>Kogia breviceps</i>.
MARINE MAMMAL SCIENCE,
17(2), 362-365.
Author URL.
Chapters
Hückstädt LA, Reisinger RR (2022). Habitat Utilization and Behavior of Phocid Seals in Relation to Oceanography. In (Ed) Ethology and Behavioral Ecology of Phocids, Springer Nature, 127-178.
Hückstädt LA (2018). Ross Seal. In (Ed) Encyclopedia of Marine Mammals, Elsevier, 835-837.
Hückstädt LA (2018). Ross Seal Ommatophoca rossii. In (Ed) Encyclopedia of Marine Mammals, Elsevier, 835-837.
Hückstädt LA (2018). Weddell Seal. In (Ed) Encyclopedia of Marine Mammals, Elsevier, 1048-1051.
Hückstädt LA (2018). Weddell Seal Leptonychotes weddellii. In (Ed) Encyclopedia of Marine Mammals, Elsevier, 1048-1051.
Conferences
Costa DP, Huckstadt LA (2020). Incorporating the movement of Marine Megafauna is critical to developing appropriate marine protected areas.
Author URL.
Costa DP, Huckstadt LA, Schwarz L, Friedlaender A, Mate B, Zerbini A, Kennedy A, Gales NJ (2018). Assessing the Potential Exposure of Migratory Animals to Disturbance.
Author URL.
Hindle AG, Bagchi A, Batten A, Levin M, Allen KN, Huckstadt LA, Costa DP, Zapol WM, Buys ES (2018). Intrinsic anti-inflammatory properties of serum in deep-diving seals.
Author URL.
Costa DP, Huckstadt LA, Villegas-Amtmann S (2018). The Importance of Body Size in Diving Mammals: Small Marine Mammals Compensate.
Author URL.
Goetz KT, Burns JM, Huckstadt LA, Shero MR, Costa DP (2017). Temporal variation in isotopic composition and diet of Weddell seals in the western Ross Sea.
Author URL.
Costa DP, Hückstädt LA, Schwarz LK, Friedlaender AS, Mate BR, Zerbini AN, Kennedy A, Gales NJ (2016). Assessing the exposure of animals to acoustic disturbance: Towards an understanding of the population consequences of disturbance. Fourth International Conference on the Effects of Noise on Aquatic Life.
Shero MR, Pearson LE, Goetz KT, Robinson PW, Hueckstaedt LA, Costa DP, Burns JM (2013). How Weddell seals stay in shape: Using morphometric and isotopic dilution techniques to assess seasonal changes in body condition.
Author URL.
Costa DP, Crocker DE, Goebel ME, Fedak MA, Mcdonald BI, Huckstadt LA (2010). Climate Change and Habitat Selection of Seals in the Western Antarctic Peninsula.
Author URL.
Huckstadt LA, Antezana T (2006). The diet of <i>Otaria flavesceins</i> in Chile:: What do we know?.
Author URL.
Publications by year
2023
Goetz KT, Dinniman MS, Hückstädt LA, Robinson PW, Shero MR, Burns JM, Hofmann EE, Stammerjohn SE, Hazen EL, Ainley DG, et al (2023). Seasonal habitat preference and foraging behaviour of post-moult Weddell seals in the western Ross Sea. Royal Society Open Science, 10(1).
Borras-Chavez R, Goebel ME, Villegas-Amtmann S, Huckstadt LA, Rivera-Rebella C, Costa DP, Farina JM, Bozinovic F (2023). Time and behavioral adjustments to lactation: Insights from a marine predator.
MARINE MAMMAL SCIENCE,
39(1), 131-150.
Author URL.
2022
Hückstädt LA, Reisinger RR (2022). Habitat Utilization and Behavior of Phocid Seals in Relation to Oceanography. In (Ed) Ethology and Behavioral Ecology of Phocids, Springer Nature, 127-178.
Conners MG, Sisson NB, Agamboue PD, Atkinson PW, Baylis AMM, Benson SR, Block BA, Bograd SJ, Bordino P, Bowen WD, et al (2022). Mismatches in scale between highly mobile marine megafauna and marine protected areas. Frontiers in Marine Science, 9
Reisinger RR, Brooks CM, Raymond B, Freer JJ, Cotté C, Xavier JC, Trathan PN, Bornemann H, Charrassin J-B, Costa DP, et al (2022). Predator-derived bioregions in the Southern Ocean: Characteristics, drivers and representation in marine protected areas. Biological Conservation, 272
Noh HJ, Turner-Maier J, Schulberg SA, Fitzgerald ML, Johnson J, Allen KN, Hückstädt LA, Batten AJ, Alfoldi J, Costa DP, et al (2022). The Antarctic Weddell seal genome reveals evidence of selection on cardiovascular phenotype and lipid handling. Communications Biology, 5(1).
Adachi T, Naito Y, Robinson PW, Costa DP, Hückstädt LA, Holser RR, Iwasaki W, Takahashi A (2022). Whiskers as hydrodynamic prey sensors in foraging seals. Proceedings of the National Academy of Sciences of the United States of America, 119(25).
2021
Pearson A, Schmitt T, Robeck T, Hückstädt L, Tift M (2021). First Report of Red Blood Cell Lifespan in a Marine Mammal: an Insight into Endogenous Carbon Monoxide (CO) Production. The FASEB Journal, 35(S1).
Adachi T, Takahashi A, Costa DP, Robinson PW, Hückstädt LA, Peterson SH, Holser RR, Beltran RS, Keates TR, Naito Y, et al (2021). Forced into an ecological corner: Round-the-clock deep foraging on small prey by elephant seals.
Science advances,
7(20).
Abstract:
Forced into an ecological corner: Round-the-clock deep foraging on small prey by elephant seals.
Small mesopelagic fishes dominate the world's total fish biomass, yet their ecological importance as prey for large marine animals is poorly understood. To reveal the little-known ecosystem dynamics, we identified prey, measured feeding events, and quantified the daily energy balance of 48 deep-diving elephant seals throughout their oceanic migrations by leveraging innovative technologies: animal-borne smart accelerometers and video cameras. Seals only attained positive energy balance after feeding 1000 to 2000 times per day on small fishes, which required continuous deep diving (80 to 100% of each day). Interspecies allometry suggests that female elephant seals have exceptional diving abilities relative to their body size, enabling them to exploit a unique foraging niche on small but abundant mesopelagic fish. This unique foraging niche requires extreme round-the-clock deep diving, limiting the behavioral plasticity of elephant seals to a changing mesopelagic ecosystem.
Abstract.
Blakeway J-A, Arnould JPY, Hoskins AJ, Martin-Cabrera P, Sutton GJ, Huckstadt LA, Costa DP, Páez-Rosas D, Villegas-Amtmann S (2021). Influence of hunting strategy on foraging efficiency in Galapagos sea lions. PeerJ, 9
Huckstadt LA, Pinones A, Palacios DM, McDonald BI, Dinniman MS, Hofmann EE, Burns JM, Crocker DE, Costa DP (2021). Projected shifts in the foraging habitat of crabeater seals along the Antarctic Peninsula (vol 10, pg 472, 2020).
NATURE CLIMATE CHANGE,
11(6), 551-551.
Author URL.
2020
Huckstadt LA, Schwarz LK, Friedlaender AS, Mate BR, Zerbini AN, Kennedy A, Robbins J, Gales NJ, Costa DP (2020). A dynamic approach to estimate the probability of exposure of marine predators to oil exploration seismic surveys over continental shelf waters.
ENDANGERED SPECIES RESEARCH,
42, 185-199.
Author URL.
Yoshino K, Takahashi A, Adachi T, Costa DP, Robinson PW, Peterson SH, Hückstädt LA, Holser RR, Naito Y (2020). Acceleration-triggered animal-borne videos show a dominance of fish in the diet of female northern elephant seals.
The Journal of experimental biology,
223(Pt 5).
Abstract:
Acceleration-triggered animal-borne videos show a dominance of fish in the diet of female northern elephant seals.
Knowledge of the diet of marine mammals is fundamental to understanding their role in marine ecosystems and response to environmental change. Recently, animal-borne video cameras have revealed the diet of marine mammals that make short foraging trips. However, novel approaches that allocate video time to target prey capture events is required to obtain diet information for species that make long foraging trips over great distances. We combined satellite telemetry and depth recorders with newly developed date-/time-, depth- and acceleration-triggered animal-borne video cameras to examine the diet of female northern elephant seals during their foraging migrations across the eastern North Pacific. We obtained 48.2
h of underwater video, from cameras mounted on the head (n=12) and jaw (n=3) of seals. Fish dominated the diet (78% of 697 prey items recorded) across all foraging locations (range: 37-55°N, 122-152°W), diving depths (range: 238-1167
m) and water temperatures (range: 3.2-7.4°C), while squid comprised only 7% of the diet. Identified prey included fish such as myctophids, Merluccius sp. and Icosteus aenigmaticus, and squid such as Histioteuthis sp. Octopoteuthis sp. and Taningia danae Our results corroborate fatty acid analysis, which also found that fish are more important in the diet, and are in contrast to stomach content analyses that found cephalopods to be the most important component of the diet. Our work shows that in situ video observation is a useful method for studying the at-sea diet of long-ranging marine predators.
Abstract.
Wright TJ, Davis RW, Holser RR, Hückstädt LA, Danesi CP, Porter C, Widen SG, Williams TM, Costa DP, Sheffield-Moore M, et al (2020). Changes in Northern Elephant Seal Skeletal Muscle Following Thirty Days of Fasting and Reduced Activity. Frontiers in Physiology, 11
Keates TR, Kudela RM, Holser RR, Huckstadt LA, Simmons SE, Costa DP (2020). Chlorophyll fluorescence as measured in situ by animal-borne instruments in the northeastern Pacific Ocean.
JOURNAL OF MARINE SYSTEMS,
203 Author URL.
Costa DP, Huckstadt LA (2020). Incorporating the movement of Marine Megafauna is critical to developing appropriate marine protected areas.
Author URL.
Hückstädt LA, Piñones A, Palacios DM, McDonald BI, Dinniman MS, Hofmann EE, Burns JM, Crocker DE, Costa DP (2020). Projected shifts in the foraging habitat of crabeater seals along the Antarctic Peninsula. Nature Climate Change, 10(5), 472-477.
Huckstadt LA, Pinones A, Palacios DM, McDonald BI, Dinniman MS, Hofmann EE, Burns JM, Crocker DE, Costa DP (2020). Projected shifts in the foraging habitat of crabeater seals along the Antarctic Peninsula (vol 56, pg 213, 2020).
NATURE CLIMATE CHANGE,
10(8), 791-791.
Author URL.
McDonald BI, Tift MS, Hückstädt LA, Jeffko M, Ponganis PJ (2020). Stroke effort and relative lung volume influence heart rate in diving sea lions.
The Journal of experimental biology,
223(Pt 5).
Abstract:
Stroke effort and relative lung volume influence heart rate in diving sea lions.
The dive response, bradycardia (decreased heart rate) and peripheral vasoconstriction, is the key mechanism allowing breath-hold divers to perform long-duration dives while actively swimming and hunting prey. This response is variable and modulated by factors such as dive duration, depth, exercise and cognitive control. This study assessed the potential role of exercise and relative lung volume in the regulation of heart rate (fH) during dives of adult female California sea lions instrumented with electrocardiogram (ECG), depth and tri-axial acceleration data loggers. A positive relationship between activity (minimum specific acceleration) and fH throughout dives suggested increased muscle perfusion associated with exercise. However, apart from late ascent, fH during dives was still less than or equal to resting fH (on land). In addition, the activity-fH relationship was weaker in long, deep dives consistent with prioritization of blood oxygen conservation over blood oxygen delivery to muscle in those dives. Pulmonary stretch receptor reflexes may also contribute to fH regulation as fH profiles generally paralleled changes in relative lung volume, especially in shallower dives and during early descent and late ascent of deeper dives. Overall, these findings support the concept that both exercise and pulmonary stretch receptor reflexes may influence the dive response in sea lions.
Abstract.
Ropert-Coudert Y, Van de Putte AP, Reisinger RR, Bornemann H, Charrassin J-B, Costa DP, Danis B, Hückstädt LA, Jonsen ID, Lea M-A, et al (2020). The retrospective analysis of Antarctic tracking data project.
Scientific data,
7(1).
Abstract:
The retrospective analysis of Antarctic tracking data project.
The Retrospective Analysis of Antarctic Tracking Data (RAATD) is a Scientific Committee for Antarctic Research project led jointly by the Expert Groups on Birds and Marine Mammals and Antarctic Biodiversity Informatics, and endorsed by the Commission for the Conservation of Antarctic Marine Living Resources. RAATD consolidated tracking data for multiple species of Antarctic meso- and top-predators to identify Areas of Ecological Significance. These datasets and accompanying syntheses provide a greater understanding of fundamental ecosystem processes in the Southern Ocean, support modelling of predator distributions under future climate scenarios and create inputs that can be incorporated into decision making processes by management authorities. In this data paper, we present the compiled tracking data from research groups that have worked in the Antarctic since the 1990s. The data are publicly available through biodiversity.aq and the Ocean Biogeographic Information System. The archive includes tracking data from over 70 contributors across 12 national Antarctic programs, and includes data from 17 predator species, 4060 individual animals, and over 2.9 million observed locations.
Abstract.
Hindell MA, Reisinger RR, Ropert-Coudert Y, Hückstädt LA, Trathan PN, Bornemann H, Charrassin J-B, Chown SL, Costa DP, Danis B, et al (2020). Tracking of marine predators to protect Southern Ocean ecosystems.
Nature,
580(7801), 87-92.
Abstract:
Tracking of marine predators to protect Southern Ocean ecosystems.
Southern Ocean ecosystems are under pressure from resource exploitation and climate change1,2. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally important region and assess current threats and protection levels. Integration of more than 4,000 tracks from 17 bird and mammal species reveals AESs around sub-Antarctic islands in the Atlantic and Indian Oceans and over the Antarctic continental shelf. Fishing pressure is disproportionately concentrated inside AESs, and climate change over the next century is predicted to impose pressure on these areas, particularly around the Antarctic continent. At present, 7.1% of the ocean south of 40°S is under formal protection, including 29% of the total AESs. The establishment and regular revision of networks of protection that encompass AESs are needed to provide long-term mitigation of growing pressures on Southern Ocean ecosystems.
Abstract.
2019
Harcourt R, Sequeira AMM, Zhang X, Roquet F, Komatsu K, Heupel M, McMahon C, Whoriskey F, Meekan M, Carroll G, et al (2019). Animal-Borne Telemetry: an Integral Component of the Ocean Observing Toolkit.
FRONTIERS IN MARINE SCIENCE,
6 Author URL.
Horning M, Andrews RD, Bishop AM, Boveng PL, Costa DP, Crocker DE, Haulena M, Hindell M, Hindle AG, Holser RR, et al (2019). Best practice recommendations for the use of external telemetry devices on pinnipeds. Animal Biotelemetry, 7(1).
Adachi T, Huckstadt LA, Tift MS, Costa DP, Naito Y, Takahashi A (2019). Inferring prey size variation from mandible acceleration in northern elephant seals.
MARINE MAMMAL SCIENCE,
35(3), 893-908.
Author URL.
Hindle AG, Allen KN, Batten AJ, Hückstädt LA, Turner-Maier J, Schulberg SA, Johnson J, Karlsson E, Lindblad-Toh K, Costa DP, et al (2019). Low guanylyl cyclase activity in Weddell seals: implications for peripheral vasoconstriction and perfusion of the brain during diving. AJP Regulatory Integrative and Comparative Physiology, 316(6), r704-r715.
Brault EK, Koch PL, Costa DP, McCarthy MD, Huckstadt LA, Goetz KT, McMahon KW, Goebel ME, Karlsson O, Teilmann J, et al (2019). Trophic position and foraging ecology of Ross, Weddell, and crabeater seals revealed by compound-specific isotope analysis.
MARINE ECOLOGY PROGRESS SERIES,
611, 1-18.
Author URL.
Keates TR, Kudela RM, Holser RR, Hückstädt LA, Simmons SE, Costa DP (2019). WITHDRAWN: Chlorophyll fluorescence as measured in situ by animal-borne instruments in the northeastern Pacific Ocean. Journal of Marine Systems
2018
Tift MS, Hückstädt LA, Ponganis PJ (2018). Anterior vena caval oxygen profiles in a deep-diving California sea lion: arteriovenous shunts, a central venous oxygen store and oxygenation during lung collapse.
The Journal of experimental biology,
221(Pt 1).
Abstract:
Anterior vena caval oxygen profiles in a deep-diving California sea lion: arteriovenous shunts, a central venous oxygen store and oxygenation during lung collapse.
Deep-diving California sea lions (Zalophus californianus) can maintain arterial hemoglobin saturation (SO2 ) above 90% despite lung collapse (lack of gas exchange) and extremely low posterior vena caval SO2 in the middle of the dive. We investigated anterior vena caval PO2 and SO2 during dives of an adult female sea lion to investigate two hypotheses: (1) posterior vena caval SO2 is not representative of the entire venous oxygen store and (2) a well-oxygenated (arterialized) central venous oxygen reservoir might account for maintenance of arterial SO2 during lung collapse. During deep dives, initial anterior vena caval SO2 was elevated at 83.6±8.4% (n=102), presumably owing to arteriovenous shunting. It remained high until the bottom phase of the dive and then decreased during ascent, whereas previously determined posterior vena caval SO2 declined during descent and then often increased during ascent. These divergent patterns confirmed that posterior vena caval SO2 was not representative of the entire venous oxygen store. Prior to and early during descent of deep dives, the high SO2 values of both the anterior and posterior venae cavae may enhance arterialization of a central venous oxygen store. However, anterior vena caval SO2 values at depths beyond lung collapse reached levels as low as 40%, making it unlikely that even a completely arterialized central venous oxygen store could account for maintenance of high arterial SO2 These findings suggest that maintenance of high arterial SO2 during deep dives is due to persistence of some gas exchange at depths beyond presumed lung collapse.
Abstract.
Costa DP, Huckstadt LA, Schwarz L, Friedlaender A, Mate B, Zerbini A, Kennedy A, Gales NJ (2018). Assessing the Potential Exposure of Migratory Animals to Disturbance.
Author URL.
Sequeira AMM, Rodríguez JP, Eguíluz VM, Harcourt R, Hindell M, Sims DW, Duarte CM, Costa DP, Fernández-Gracia J, Ferreira LC, et al (2018). Convergence of marine megafauna movement patterns in coastal and open oceans.
Proc Natl Acad Sci U S A,
115(12), 3072-3077.
Abstract:
Convergence of marine megafauna movement patterns in coastal and open oceans.
The extent of increasing anthropogenic impacts on large marine vertebrates partly depends on the animals' movement patterns. Effective conservation requires identification of the key drivers of movement including intrinsic properties and extrinsic constraints associated with the dynamic nature of the environments the animals inhabit. However, the relative importance of intrinsic versus extrinsic factors remains elusive. We analyze a global dataset of ∼2.8 million locations from >2,600 tracked individuals across 50 marine vertebrates evolutionarily separated by millions of years and using different locomotion modes (fly, swim, walk/paddle). Strikingly, movement patterns show a remarkable convergence, being strongly conserved across species and independent of body length and mass, despite these traits ranging over 10 orders of magnitude among the species studied. This represents a fundamental difference between marine and terrestrial vertebrates not previously identified, likely linked to the reduced costs of locomotion in water. Movement patterns were primarily explained by the interaction between species-specific traits and the habitat(s) they move through, resulting in complex movement patterns when moving close to coasts compared with more predictable patterns when moving in open oceans. This distinct difference may be associated with greater complexity within coastal microhabitats, highlighting a critical role of preferred habitat in shaping marine vertebrate global movements. Efforts to develop understanding of the characteristics of vertebrate movement should consider the habitat(s) through which they move to identify how movement patterns will alter with forecasted severe ocean changes, such as reduced Arctic sea ice cover, sea level rise, and declining oxygen content.
Abstract.
Author URL.
Bagchi A, Batten AJ, Levin M, Allen KN, Fitzgerald ML, Hückstädt LA, Costa DP, Buys ES, Hindle AG (2018). Intrinsic anti-inflammatory properties in the serum of two species of deep-diving seal.
The Journal of experimental biology,
221(Pt 13).
Abstract:
Intrinsic anti-inflammatory properties in the serum of two species of deep-diving seal.
Weddell and elephant seals are deep-diving mammals, which rely on lung collapse to limit nitrogen absorption and prevent decompression injury. Repeated collapse and re-expansion exposes the lungs to multiple stressors, including ischemia-reperfusion, alveolar shear stress and inflammation. There is no evidence, however, that diving damages pulmonary function in these species. To investigate potential protective strategies in deep-diving seals, we examined the inflammatory response of seal whole blood exposed to lipopolysaccharide (LPS), a potent endotoxin. Interleukin-6 (IL6) cytokine production elicited by LPS exposure was 50 to 500 times lower in blood of healthy northern elephant seals and Weddell seals compared with that of healthy human blood. In contrast to the ∼6× increased production of IL6 protein from LPS-exposed Weddell seal whole blood, isolated Weddell seal peripheral blood mononuclear cells, under standard cell culture conditions using medium supplemented with fetal bovine serum (FBS), produced a robust LPS response (∼300×). Induction of Il6 mRNA expression as well as production of IL6, IL8, IL10, KC-like and TNFα were reduced by substituting FBS with an equivalent amount of autologous seal serum. Weddell seal serum also attenuated the inflammatory response of RAW 267.4 mouse macrophage cells exposed to LPS. Cortisol level and the addition of serum lipids did not impact the cytokine response in cultured cells. These data suggest that seal serum possesses anti-inflammatory properties, which may protect deep divers from naturally occurring inflammatory challenges such as dive-induced hypoxia-reoxygenation and lung collapse.
Abstract.
Hindle AG, Bagchi A, Batten A, Levin M, Allen KN, Huckstadt LA, Costa DP, Zapol WM, Buys ES (2018). Intrinsic anti-inflammatory properties of serum in deep-diving seals.
Author URL.
Hindle AG, Bagchi A, Batten A, Levin M, Allen KN, Huckstadt LA, Costa DP, Zapol WM, Buys ES (2018). Intrinsic anti‐inflammatory properties of serum in deep‐diving seals. The FASEB Journal, 32(S1), 859.9-859.9.
Kooyman GL, van Dam RP, Hückstädt LA (2018). Night diving by some emperor penguins during the winter breeding period at Cape Washington.
The Journal of experimental biology,
221(Pt 1).
Abstract:
Night diving by some emperor penguins during the winter breeding period at Cape Washington.
All through the bird literature and feature films, there is much ado about dedicated emperor penguin males fasting for 115
days while they do all the incubation of the single egg. Sometimes, they may not fast for so long. Based on a winter visit to Cape Washington, we obtained evidence that some birds may feed before the egg is laid, and if they do, and some are males, then their fast is much less than 115
days. The consequence of a shorter fast for the male is a better chance of completing the 65 day incubation fast and success in fledging the chick. For those in northern colonies that may migrate south, there will be closer access to open water, but there will be the need to dive in the dark.
Abstract.
Hückstädt LA (2018). Ross Seal. In (Ed) Encyclopedia of Marine Mammals, Elsevier, 835-837.
Hückstädt LA (2018). Ross Seal Ommatophoca rossii. In (Ed) Encyclopedia of Marine Mammals, Elsevier, 835-837.
Costa DP, Huckstadt LA, Villegas-Amtmann S (2018). The Importance of Body Size in Diving Mammals: Small Marine Mammals Compensate.
Author URL.
McHuron EA, Peterson SH, Hückstädt LA, Melin SR, Harris JD, Costa DP (2018). The energetic consequences of behavioral variation in a marine carnivore.
Ecology and evolution,
8(8), 4340-4351.
Abstract:
The energetic consequences of behavioral variation in a marine carnivore.
Intraspecific variability in foraging behavior has been documented across a range of taxonomic groups, yet the energetic consequences of this variation are not well understood for many species. Understanding the effect of behavioral variation on energy expenditure and acquisition is particularly crucial for mammalian carnivores because they have high energy requirements that place considerable pressure on prey populations. To determine the influence of behavior on energy expenditure and balance, we combined simultaneous measurements of at-sea field metabolic rate (FMR) and foraging behavior in a marine carnivore that exhibits intraspecific behavioral variation, the California sea lion (Zalophus californianus). Sea lions exhibited variability in at-sea FMR, with some individuals expending energy at a maximum of twice the rate of others. This variation was in part attributable to differences in diving behavior that may have been reflective of diet; however, this was only true for sea lions using a foraging strategy consisting of epipelagic (
Abstract.
Hückstädt LA, Holser RR, Tift MS, Costa DP (2018). The extra burden of motherhood: reduced dive duration associated with pregnancy status in a deep-diving mammal, the northern elephant seal.
Biology letters,
14(2).
Abstract:
The extra burden of motherhood: reduced dive duration associated with pregnancy status in a deep-diving mammal, the northern elephant seal.
The cost of pregnancy is hard to study in marine mammals, particularly in species that undergo pregnancy while diving continuously at sea such as elephant seals (genus Mirounga). We analysed the diving behaviour of confirmed pregnant and non-pregnant northern elephant seals (M. angustirostris, n = 172) and showed that after an initial continuous increase in dive duration, dives of pregnant females become shorter after week 17. The reasons for this reduction in dive duration remain unknown, but we hypothesize that increased fetal demand for oxygen could be the cause. Our findings reveal an opportunity to explore the use of biologging data to investigate pregnancy status of free-ranging marine mammals and factors that could affect pregnancy success.
Abstract.
Hückstädt LA (2018). Weddell Seal. In (Ed) Encyclopedia of Marine Mammals, Elsevier, 1048-1051.
Hückstädt LA (2018). Weddell Seal Leptonychotes weddellii. In (Ed) Encyclopedia of Marine Mammals, Elsevier, 1048-1051.
2017
Pirotta E, Mangel M, Costa DP, Mate B, Goldbogen JA, Palacios DM, Hückstädt LA, McHuron EA, Schwarz L, New L, et al (2017). A Dynamic State Model of Migratory Behavior and Physiology to Assess the Consequences of Environmental Variation and Anthropogenic Disturbance on Marine Vertebrates.
The American naturalist,
191(2), E40-E56.
Abstract:
A Dynamic State Model of Migratory Behavior and Physiology to Assess the Consequences of Environmental Variation and Anthropogenic Disturbance on Marine Vertebrates.
Integrating behavior and physiology is critical to formulating new hypotheses on the evolution of animal life-history strategies. Migratory capital breeders acquire most of the energy they need to sustain migration, gestation, and lactation before parturition. Therefore, when predicting the impact of environmental variation on such species, a mechanistic understanding of the physiology of their migratory behavior is required. Using baleen whales as a model system, we developed a dynamic state variable model that captures the interplay among behavioral decisions, energy, reproductive needs, and the environment. We applied the framework to blue whales (Balaenoptera musculus) in the eastern North Pacific Ocean and explored the effects of environmental and anthropogenic perturbations on female reproductive success. We demonstrate the emergence of migration to track prey resources, enabling us to quantify the trade-offs among capital breeding, body condition, and metabolic expenses. We predict that periodic climatic oscillations affect reproductive success less than unprecedented environmental changes do. The effect of localized, acute anthropogenic impacts depended on whales' behavioral response to the disturbance; chronic, but weaker, disturbances had little effect on reproductive success. Because we link behavior and vital rates by modeling individuals' energetic budgets, we provide a general framework to investigate the ecology of migration and assess the population consequences of disturbance, while identifying critical knowledge gaps.
Abstract.
Tift MS, Hückstädt LA, McDonald BI, Thorson PH, Ponganis PJ (2017). Flipper stroke rate and venous oxygen levels in free-ranging California sea lions.
The Journal of experimental biology,
220(Pt 8), 1533-1540.
Abstract:
Flipper stroke rate and venous oxygen levels in free-ranging California sea lions.
The depletion rate of the blood oxygen store, development of hypoxemia and dive capacity are dependent on the distribution and rate of blood oxygen delivery to tissues while diving. Although blood oxygen extraction by working muscle would increase the blood oxygen depletion rate in a swimming animal, there is little information on the relationship between muscle workload and blood oxygen depletion during dives. Therefore, we examined flipper stroke rate, a proxy of muscle workload, and posterior vena cava oxygen profiles in four adult female California sea lions (Zalophus californianus) during foraging trips at sea. Flipper stroke rate analysis revealed that sea lions minimized muscle metabolism with a stroke-glide strategy when diving, and exhibited prolonged glides during the descent of deeper dives (>100
m). During the descent phase of these deep dives, 55±21% of descent was spent gliding, with the longest glides lasting over 160
s and covering a vertical distance of 340
m. Animals also consistently glided to the surface from 15 to 25
m depth during these deeper dives. Venous hemoglobin saturation (SO2 ) profiles were highly variable throughout dives, with values occasionally increasing during shallow dives. The relationship between SO2 and flipper stroke rate was weak during deeper dives, while this relationship was stronger during shallow dives. We conclude that (1) the depletion of oxygen in the posterior vena cava in deep-diving sea lions is not dependent on stroke effort, and (2) stroke-glide patterns during dives contribute to a reduction of muscle metabolic rate.
Abstract.
Roquet F, Boehme L, Block B, Charrassin J-B, Costa D, Guinet C, Harcourt RG, Hindell MA, Huckstadt LA, McMahon CR, et al (2017). Ocean Observations Using Tagged Animals.
OCEANOGRAPHY,
30(2), 139-139.
Author URL.
Goetz KT, Burns JM, Huckstadt LA, Shero MR, Costa DP (2017). Temporal variation in isotopic composition and diet of Weddell seals in the western Ross Sea.
Author URL.
Hückstädt LA, McCarthy MD, Koch PL, Costa DP (2017). What difference does a century make? Shifts in the ecosystem structure of the Ross Sea, Antarctica, as evidenced from a sentinel species, the Weddell seal.
Proceedings. Biological sciences,
284(1861).
Abstract:
What difference does a century make? Shifts in the ecosystem structure of the Ross Sea, Antarctica, as evidenced from a sentinel species, the Weddell seal.
The arrival of humans to Antarctica's Ross Sea (100+ years ago) led to a slow, but sustained increase in human activities in the area. To investigate if human presence has influenced the structure of the ecosystem over the last century, we compared historical (ca 100 years old) and modern samples of a sentinel species, the Weddell seal (Leptonychotes weddellii), using both bulk tissue and compound-specific stable isotope analysis. The historical isotopic niche of Weddell seals was over five times larger than the modern niche. The isotopic values of individual amino acids showed a clear segregation between historical and modern samples, indicative of differences at the base of the trophic web. Further, we found no significant differences in the trophic position of Weddell seals between the two periods. Our study revealed that the Ross Sea has undergone detectable changes (i.e. in the primary producers community) in the last century, but the presence of humans has not disrupted trophic interactions supporting Weddell seals.
Abstract.
2016
Fiechter J, Huckstadt LA, Rose KA, Costa DP (2016). A fully coupled ecosystem model to predict the foraging ecology of apex predators in the California Current.
MARINE ECOLOGY PROGRESS SERIES,
556, 273-285.
Author URL.
Fregosi S, Klinck H, Horning M, Costa DP, Mann D, Sexton K, Hückstädt LA, Mellinger DK, Southall BL (2016). An animal-borne active acoustic tag for minimally invasive behavioral response studies on marine mammals. Animal Biotelemetry, 4(1).
Costa DP, Hückstädt LA, Schwarz LK, Friedlaender AS, Mate BR, Zerbini AN, Kennedy A, Gales NJ (2016). Assessing the exposure of animals to acoustic disturbance: Towards an understanding of the population consequences of disturbance. Fourth International Conference on the Effects of Noise on Aquatic Life.
Hindell MA, McMahon CR, Bester MN, Boehme L, Costa D, Fedak MA, Guinet C, Herraiz-Borreguero L, Harcourt RG, Huckstadt L, et al (2016). Circumpolar habitat use in the southern elephant seal: implications for foraging success and population trajectories.
ECOSPHERE,
7(5).
Author URL.
Riet-Sapriza FG, Costa DP, Franco-Trecu V, Marin Y, Chocca J, Gonzalez B, Beathyate G, Chilvers BL, Huckstadt LA (2016). Foraging behavior of lactating South American sea lions (<i>Otaria flavescens</i>) and spatial-temporal resource overlap with the Uruguayan fisheries (vol 88, pg 106, 2013).
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY,
132, 267-268.
Author URL.
Hückstädt LA, Tift MS, Riet-Sapriza F, Franco-Trecu V, Baylis AMM, Orben RA, Arnould JPY, Sepulveda M, Santos-Carvallo M, Burns JM, et al (2016). Regional variability in diving physiology and behavior in a widely distributed air-breathing marine predator, the South American sea lion (Otaria byronia).
The Journal of experimental biology,
219(Pt 15), 2320-2330.
Abstract:
Regional variability in diving physiology and behavior in a widely distributed air-breathing marine predator, the South American sea lion (Otaria byronia).
Our understanding of how air-breathing marine predators cope with environmental variability is limited by our inadequate knowledge of their ecological and physiological parameters. Because of their wide distribution along both coasts of the sub-continent, South American sea lions (Otaria byronia) provide a valuable opportunity to study the behavioral and physiological plasticity of a marine predator in different environments. We measured the oxygen stores and diving behavior of South American sea lions throughout most of its range, allowing us to demonstrate that diving ability and behavior vary across its range. We found no significant differences in mass-specific blood volumes of sea lions among field sites and a negative relationship between mass-specific oxygen storage and size, which suggests that exposure to different habitats and geographical locations better explains oxygen storage capacities and diving capability in South American sea lions than body size alone. The largest animals in our study (individuals from Uruguay) were the shallowest and shortest duration divers, and had the lowest mass-specific total body oxygen stores, while the deepest and longest duration divers (individuals from southern Chile) had significantly larger mass-specific oxygen stores, despite being much smaller animals. Our study suggests that the physiology of air-breathing diving predators is not fixed, but that it can be adjusted, to a certain extent, depending on the ecological setting and or habitat. These adjustments can be thought of as a 'training effect': as the animal continues to push its physiological capacity through greater hypoxic exposure, its breath-holding capacity increases.
Abstract.
Beltran RS, Peterson SH, McHuron EA, Reichmuth C, Hückstädt LA, Costa DP (2016). Seals and sea lions are what they eat, plus what? Determination of trophic discrimination factors for seven pinniped species.
Rapid communications in mass spectrometry : RCM,
30(9), 1115-1122.
Abstract:
Seals and sea lions are what they eat, plus what? Determination of trophic discrimination factors for seven pinniped species.
RationaleMixing models are a common method for quantifying the contribution of prey sources to the diet of an individual using stable isotope analysis; however, these models rely upon a known trophic discrimination factor (hereafter, TDF) that results from fractionation between prey and animal tissues. Quantifying TDFs in captive animals is ideal, because diet is controlled and the proportional contributions and isotopic values of all prey items are known.MethodsTo calculate TDFs for the Hawaiian monk seal, northern elephant seal, bearded seal, ringed seal, spotted seal, harbor seal, and California sea lion, we obtained whiskers, serum, plasma, red blood cells, and prey items from nine captive individuals. We obtained δ(13) C and δ(15) N values using continuous-flow isotope-ratio mass spectrometry. The average δ(13) C and δ(15) N values from bulk and lipid-corrected prey from the diet were subtracted from the δ(13) C and δ(15) N values of each blood and whisker sample to calculate tissue-specific TDFs for each individual (∆(13) C or ∆(15) N).ResultsThe ∆(13) C values ranged from +1.7 to +3.2‰ (bulk prey) and from +0.8 to +1.9‰ (lipid-corrected prey) for the various blood components, and from +3.9 to +4.6‰ (bulk prey) or +2.6 to +3.9‰ (lipid-corrected prey) for whiskers. The ∆(15) N values ranged from +2.2 to +4.3‰ for blood components and from +2.6 to +4.0‰ for whiskers. The TDFs tended to group by tissue, with whiskers having greater ∆(13) C values than blood components. In contrast, the ∆(15) N values were greater in serum and plasma than in red blood cells and whiskers.ConclusionsBy providing the first TDF values for five seal species (family Phocidae) and one otariid species (family Otariidae), our study facilitates more accurate mixing models for these species. These values are particularly important for critically endangered Hawaiian monk seals and the three Arctic seal species (bearded, ringed, and spotted) that are faced with a rapidly changing environment.
Abstract.
2015
Schwarz LK, Villegas-Amtmann S, Beltran RS, Costa DP, Goetsch C, Hückstädt L, Maresh JL, Peterson SH (2015). Comparisons and Uncertainty in Fat and Adipose Tissue Estimation Techniques: the Northern Elephant Seal as a Case Study.
PloS one,
10(6).
Abstract:
Comparisons and Uncertainty in Fat and Adipose Tissue Estimation Techniques: the Northern Elephant Seal as a Case Study.
Fat mass and body condition are important metrics in bioenergetics and physiological studies. They can also link foraging success with demographic rates, making them key components of models that predict population-level outcomes of environmental change. Therefore, it is important to incorporate uncertainty in physiological indicators if results will lead to species management decisions. Maternal fat mass in elephant seals (Mirounga spp) can predict reproductive rate and pup survival, but no one has quantified or identified the sources of uncertainty for the two fat mass estimation techniques (labeled-water and truncated cones). The current cones method can provide estimates of proportion adipose tissue in adult females and proportion fat of juveniles in northern elephant seals (M. angustirostris) comparable to labeled-water methods, but it does not work for all cases or species. We reviewed components and assumptions of the technique via measurements of seven early-molt and seven late-molt adult females. We show that seals are elliptical on land, rather than the assumed circular shape, and skin may account for a high proportion of what is often defined as blubber. Also, blubber extends past the neck-to-pelvis region, and comparisons of new and old ultrasound instrumentation indicate previous measurements of sculp thickness may be biased low. Accounting for such differences, and incorporating new measurements of blubber density and proportion of fat in blubber, we propose a modified cones method that can isolate blubber from non-blubber adipose tissue and separate fat into skin, blubber, and core compartments. Lastly, we found that adipose tissue and fat estimates using tritiated water may be biased high during the early molt. Both the tritiated water and modified cones methods had high, but reducible, uncertainty. The improved cones method for estimating body condition allows for more accurate quantification of the various tissue masses and may also be transferrable to other species.
Abstract.
Lawson GL, Hückstädt LA, Lavery AC, Jaffré FM, Wiebe PH, Fincke JR, Crocker DE, Costa DP (2015). Development of an animal-borne “sonar tag” for quantifying prey availability: test deployments on northern elephant seals. Animal Biotelemetry, 3(1).
(2015). Hydrurga leptonyx: Hückstädt, L.
Sepúlveda M, Newsome SD, Pavez G, Oliva D, Costa DP, Hückstädt LA (2015). Using Satellite Tracking and Isotopic Information to Characterize the Impact of South American Sea Lions on Salmonid Aquaculture in Southern Chile.
PloS one,
10(8).
Abstract:
Using Satellite Tracking and Isotopic Information to Characterize the Impact of South American Sea Lions on Salmonid Aquaculture in Southern Chile.
Apex marine predators alter their foraging behavior in response to spatial and/or seasonal changes in natural prey distribution and abundance. However, few studies have identified the impacts of aquaculture that represents a spatially and temporally predictable and abundant resource on their foraging behavior. Using satellite telemetry and stable isotope analysis we examined the degree of spatial overlap between the South American sea lion (SASL) and salmon farms, and quantify the amount of native prey versus farmed salmonids in SASL diets. We instrumented eight SASL individuals with SRDL-GPS tags. Vibrissae, hair and skin samples were collected for δ13C and δ15N analyses from five of the tagged individuals and from four males captured in a haul-out located adjacent to salmon farms. Tracking results showed that almost all the foraging areas of SASL are within close proximity to salmon farms. The most important prey for the individuals analyzed was farmed salmonids, with an estimated median (±SD) contribution of 19.7 ± 13.5‰ and 15.3 ± 9.6‰ for hair and skin, respectively. Using vibrissae as a temporal record of diet for each individual, we observed a remarkable switch in diet composition in two SASL, from farmed salmonids to pelagic fishes, which coincided with the decrease of salmon production due to the infectious salmon anemia virus that affected salmon farms in Chile at the end of 2008. Our study demonstrates the usefulness of integrating stable isotope derived dietary data with movement patterns to characterize the impacts of a non-native prey on the foraging ecology of an apex marine predator, providing important applied implications in situations where interactions between aquaculture and wildlife are common.
Abstract.
2014
(2014). Leptonychotes weddellii: Hückstädt, L.
(2014). Lobodon carcinophaga: Hückstädt, L.
(2014). Mirounga angustirostris: Hückstädt, L.
Hueckstaedt LA, Quinones RA, Sepulveda M, Costa DP (2014). Movement and diving patterns of juvenile male South American sea lions off the coast of central Chile.
MARINE MAMMAL SCIENCE,
30(3), 1175-1183.
Author URL.
(2014). Ommatophoca rossii: Hückstädt, L.
2013
Roquet F, Wunsch C, Forget G, Heimbach P, Guinet C, Reverdin G, Charrassin J-B, Bailleul F, Costa DP, Huckstadt LA, et al (2013). Estimates of the Southern Ocean general circulation improved by animal-borne instruments.
GEOPHYSICAL RESEARCH LETTERS,
40(23), 6176-6180.
Author URL.
Riet-Sapriza FG, Costa DP, Franco-Trecu V, Marin Y, Chocca J, Gonzalez B, Beathyate G, Chilvers BL, Hueckstadt LA (2013). Foraging behavior of lactating South American sea lions (<i>Otaria flavescens</i>) and spatial-temporal resource overlap with the Uruguayan fisheries.
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY,
88-89, 106-119.
Author URL.
Shero MR, Pearson LE, Goetz KT, Robinson PW, Hueckstaedt LA, Costa DP, Burns JM (2013). How Weddell seals stay in shape: Using morphometric and isotopic dilution techniques to assess seasonal changes in body condition.
Author URL.
Fregosi S, Klinck H, Horning M, Mellinger DK, Costa DP, Mann DA, Sexton K, Huckstadt L (2013). Use of an animal-borne active acoustic tag to conduct minimally-invasive behavioral response studies.
The Journal of the Acoustical Society of America,
134(5_Supplement), 4044-4044.
Abstract:
Use of an animal-borne active acoustic tag to conduct minimally-invasive behavioral response studies
A pilot study was conducted to evaluate the potential of animal-borne active and passive acoustic tags for conducting minimally-invasive behavioral response studies on pinnipeds. A prototype tag was developed and tested on juvenile northern elephant seals (Mirounga angustirostris) using translocation experiments at Año Nuevo State Park, CA, USA, in spring 2012. The principal scientific questions of this pilot study were (1) do low-intensity sounds emitted by an animal-borne tag elicit behavioral responses, and (2) are potential animal responses related to signal content (e.g. threatening vs non-threatening)? Preliminary results indicate that (1) low-intensity sounds emitted by animal-borne tags elicit distinct behavioral responses, (2) these responses appear related to signal content, and (3) the responses may differ based on depth, bathymetry, and location. The results of the study show the promise of this approach as a minimally invasive and cost-effective method to investigate animal responses to underwater sounds, as well as a method to develop mitigation strategies. We are currently in the process of improving the tag design for future field efforts with the goal to increase the sample size, range of acoustic stimuli, and age/sex classes of tagged seals. [Funding from NOAA/NMFS Ocean Acoustics Program.]
Abstract.
2012
Klinck H, Horning M, Mellinger DK, Costa DP, Fregosi S, Mann DA, Sexton K, Huckstadt L (2012). Animal-borne active acoustic tags: a new paradigm to conduct minimally invasive behavioral response studies?.
The Journal of the Acoustical Society of America,
132(3_Supplement), 2009-2009.
Abstract:
Animal-borne active acoustic tags: a new paradigm to conduct minimally invasive behavioral response studies?
In 2011 a pilot study was begun to evaluate the potential of animal-borne active acoustic tags for conducting minimally-invasive behavioral response studies on pinnipeds. A basic prototype tag was developed and tested on juvenile northern elephant seals (Mirounga angustirostris) during translocation experiments at Año Nuevo State Park, CA, USA in spring 2012. The principal scientific questions of this pilot study were these: (1) do sounds emitted from an animal-borne low acoustic intensity tag elicit behavioral responses, and (2) are potential animal responses related to signal content (e.g. threatening vs. non-threatening). Although the sample size was small, preliminary results indicate that (1) low-intensity sounds emitted by animal-borne tags elicit distinct behavioral responses, (2) these responses appear related to signal content, and (3) the responses may differ based on depth, bathymetry, and location. The results of the conducted study show the promise of this approach as a minimally-invasive and cost-effective method to investigate animal responses to underwater sounds, as well as a method to develop mitigation strategies. Future efforts would increase the sample size, range of acoustic stimuli, and age/sex classes of tagged seals. [Funding from NOAA/NMFS Ocean Acoustics Program.]
Abstract.
Hueckstaedt LA, Burns JM, Koch PL, McDonald BI, Crocker DE, Costa DP (2012). Diet of a specialist in a changing environment: the crabeater seal along the western Antarctic Peninsula.
MARINE ECOLOGY PROGRESS SERIES,
455, 287-301.
Author URL.
Robinson PW, Costa DP, Crocker DE, Gallo-Reynoso JP, Champagne CD, Fowler MA, Goetsch C, Goetz KT, Hassrick JL, Hückstädt LA, et al (2012). Foraging behavior and success of a mesopelagic predator in the northeast Pacific Ocean: insights from a data-rich species, the northern elephant seal.
PloS one,
7(5).
Abstract:
Foraging behavior and success of a mesopelagic predator in the northeast Pacific Ocean: insights from a data-rich species, the northern elephant seal.
The mesopelagic zone of the northeast Pacific Ocean is an important foraging habitat for many predators, yet few studies have addressed the factors driving basin-scale predator distributions or inter-annual variability in foraging and breeding success. Understanding these processes is critical to reveal how conditions at sea cascade to population-level effects. To begin addressing these challenging questions, we collected diving, tracking, foraging success, and natality data for 297 adult female northern elephant seal migrations from 2004 to 2010. During the longer post-molting migration, individual energy gain rates were significant predictors of pregnancy. At sea, seals focused their foraging effort along a narrow band corresponding to the boundary between the sub-arctic and sub-tropical gyres. In contrast to shallow-diving predators, elephant seals target the gyre-gyre boundary throughout the year rather than follow the southward winter migration of surface features, such as the Transition Zone Chlorophyll Front. We also assessed the impact of added transit costs by studying seals at a colony near the southern extent of the species' range, 1,150 km to the south. A much larger proportion of seals foraged locally, implying plasticity in foraging strategies and possibly prey type. While these findings are derived from a single species, the results may provide insight to the foraging patterns of many other meso-pelagic predators in the northeast Pacific Ocean.
Abstract.
Padman L, Costa DP, Dinniman MS, Fricker HA, Goebel ME, Huckstadt LA, Humbert A, Joughin I, Lenaerts JTM, Ligtenberg SRM, et al (2012). Oceanic controls on the mass balance of Wilkins Ice Shelf, Antarctica.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS,
117 Author URL.
2011
Chilvers BL, Amey JM, Huckstadt LA, Costa DP (2011). Investigating foraging utilization distribution of female New Zealand sea lions, Auckland Islands.
POLAR BIOLOGY,
34(4), 565-574.
Author URL.
Villegas-Amtmann S, Simmons SE, Kuhn CE, Huckstadt LA, Costa DP (2011). Latitudinal range influences the seasonal variation in the foraging behavior of marine top predators.
PloS one,
6(8).
Abstract:
Latitudinal range influences the seasonal variation in the foraging behavior of marine top predators.
Non-migratory resident species should be capable of modifying their foraging behavior to accommodate changes in prey abundance and availability associated with a changing environment. Populations that are better adapted to change will have higher foraging success and greater potential for survival in the face of climate change. We studied two species of resident central place foragers from temperate and equatorial regions with differing population trends and prey availability associated to season, the California sea lion (Zalophus californianus) (CSL) whose population is increasing and the endangered Galapagos sea lion (Zalophus wollebaeki) (GSL) whose population is declining. To determine their response to environmental change, we studied and compared their diving behavior using time-depth recorders and satellite location tags and their diet by measuring C and N isotope ratios during a warm and a cold season. Based on latitudinal differences in oceanographic productivity, we hypothesized that the seasonal variation in foraging behavior would differ for these two species. CSL exhibited greater seasonal variability in their foraging behavior as seen in changes to their diving behavior, foraging areas and diet between seasons. Conversely, GSL did not change their diving behavior between seasons, presenting three foraging strategies (shallow, deep and bottom divers) during both. GSL exhibited greater dive and foraging effort than CSL. We suggest that during the warm and less productive season a greater range of foraging behaviors in CSL was associated with greater competition for prey, which relaxed during the cold season when resource availability was greater. GSL foraging specialization suggests that resources are limited throughout the year due to lower primary production and lower seasonal variation in productivity compared to CSL. These latitudinal differences influence their foraging success, pup survival and population growth reflected in contrasting population trends in which CSL are more successful and potentially more resilient to climate change.
Abstract.
Hückstädt LA, Koch PL, McDonald BI, Goebel ME, Crocker DE, Costa DP (2011). Stable isotope analyses reveal individual variability in the trophic ecology of a top marine predator, the southern elephant seal.
Oecologia,
169(2), 395-406.
Abstract:
Stable isotope analyses reveal individual variability in the trophic ecology of a top marine predator, the southern elephant seal.
Identifying individuals' foraging strategies is critical to understanding the ecology of a species, and can provide the means to predict possible ecological responses to environmental change. Our study combines stable isotope analysis and satellite telemetry to study the variability in individual foraging strategies of adult female southern elephant seals (Mirounga leonina). Our hypothesis is that female elephant seals from the Western Antarctica Peninsula (WAP) display individual specialization in their diets. We captured adult female elephant seals (n = 56, 2005-2009) at Livingston Island (Antarctica), and instrumented them with SMRU-CTD satellite tags. We collected blood, fur, and vibrissae samples for δ(13)C and δ(15)N analyses. The mean values for all vibrissae were -21.0 ± 0.7‰ for δ(13)C, and 10.4 ± 0.8‰, for δ(15)N. The individual variability of δ(13)C (60%) was more important than the within-individual variability (40%) in explaining the total variance observed in our data. For δ(15)N, the results showed the opposite trend, with the within-individual variability (64%) contributing more to the total variance than the individual variability (36%), likely associated with the effect that the fasting periods have on δ(15)N values. Most individuals were specialists, as inferred from the low intra-individual variability of δ(13)C values with respect to the population variability, with half the individuals utilizing 31% or less of their available niche. We found eight different foraging strategies for these animals. Female elephant seals from the WAP are a diverse group of predators with individuals utilizing only a small portion of the total available niche, with the consequent potential to expand their foraging habits to exploit other resources or environments in the Southern Ocean.
Abstract.
2010
Costa DP, Huckstadt LA, Crocker DE, McDonald BI, Goebel ME, Fedak MA (2010). Approaches to studying climatic change and its role on the habitat selection of antarctic pinnipeds.
Integrative and comparative biology,
50(6), 1018-1030.
Abstract:
Approaches to studying climatic change and its role on the habitat selection of antarctic pinnipeds.
Top predators integrate resources over time and space, and depending on the particular species they represent, different components of the marine environment. The habitat utilization of top predators has been studied using electronic tags to follow their movements and foraging behavior. In addition, these tags provide information on the physical characteristics of the water column (temperature and salinity) at a scale and resolution that is coincident with the animals' behavior. In addition to data on the animals' behavior, these tags provide physical oceanographic data in regions or at times they cannot be collected using other currently available technologies. These data inform us on how these important top predators are likely to respond to climatic change, as well as about how the Southern Ocean is changing.
Abstract.
Costa DP, Crocker DE, Goebel ME, Fedak MA, Mcdonald BI, Huckstadt LA (2010). Climate Change and Habitat Selection of Seals in the Western Antarctic Peninsula.
Author URL.
Padman L, Costa DP, Bolmer ST, Goebel ME, Huckstadt LA, Jenkins A, McDonald BI, Shoosmith DR (2010). Seals map bathymetry of the Antarctic continental shelf.
GEOPHYSICAL RESEARCH LETTERS,
37 Author URL.
2007
Huckstadt LA, Rojas CP, Antezana T (2007). Stable isotope analysis reveals pelagic foraging by the Southern sea lion in central Chile.
JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY,
347(1-2), 123-133.
Author URL.
2006
Huckstadt LA, Antezana T (2006). The diet of <i>Otaria flavesceins</i> in Chile:: What do we know?.
Author URL.
2005
Hückstädt LA (2005). Nuevos registros de cetAceos para la VIII RegiOn, Chile (1997 a 1999). Gayana (Concepción), 69(2).
2004
Hückstädt LA, Antezana T (2004). Behaviour of Southern sea lions in presence of killer whales during fishing operations in Central Chile.
SCIENTIA MARINA,
68(2), 295-298.
Author URL.
Hückstädt LA, Krautz MC (2004). Interaction between southern sea lions <i>Otaria flavescens</i> and jack mackerel <i>Trachurus symmetricus</i> commercial fishery off Central Chile:: a geostatistical approach.
MARINE ECOLOGY PROGRESS SERIES,
282, 285-294.
Author URL.
2003
Hückstädt LA, Antezana T (2003). Behaviour of the southern sea lion (<i>Otaria flavescens</i>) and consumption of the catch during purse-seining for jack mackerel (<i>Trachurus symmetricus</i>) off central Chile.
ICES JOURNAL OF MARINE SCIENCE,
60(5), 1003-1011.
Author URL.
2001
Hückstädt L, Antezana T (2001). An observation of parturition in a stranded <i>Kogia breviceps</i>.
MARINE MAMMAL SCIENCE,
17(2), 362-365.
Author URL.