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Bender AN, Krause DJ, Goebel ME, Hoffman JI, Lewallen EA, Bonin CA. Genetic diversity and demographic history of the leopard seal: A Southern Ocean top predator. PLoS One 2023; 18:e0284640. [PMID: 37566609 PMCID: PMC10420386 DOI: 10.1371/journal.pone.0284640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 06/14/2023] [Indexed: 08/13/2023] Open
Abstract
Leopard seals (Hydrurga leptonyx) are top predators that can exert substantial top-down control of their Antarctic prey species. However, population trends and genetic diversity of leopard seals remain understudied, limiting our understanding of their ecological role. We investigated the genetic diversity, effective population size and demographic history of leopard seals to provide fundamental data that contextualizes their predatory influence on Antarctic ecosystems. Ninety leopard seals were sampled from the northern Antarctic Peninsula during the austral summers of 2008-2019 and a 405bp segment of the mitochondrial control region was sequenced for each individual. We uncovered moderate levels of nucleotide (π = 0.013) and haplotype (Hd = 0.96) diversity, and the effective population size was estimated at around 24,000 individuals (NE = 24,376; 95% CI: 16,876-33,126). Consistent with findings from other ice-breeding pinnipeds, Bayesian skyline analysis also revealed evidence for population expansion during the last glacial maximum, suggesting that historical population growth may have been boosted by an increase in the abundance of sea ice. Although leopard seals can be found in warmer, sub-Antarctic locations, the species' core habitat is centered on the Antarctic, making it inherently vulnerable to the loss of sea ice habitat due to climate change. Therefore, detailed assessments of past and present leopard seal population trends are needed to inform policies for Antarctic ecosystems.
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Affiliation(s)
- Arona N. Bender
- Marine and Environmental Sciences Department, Hampton University, Hampton, VA, United States of America
| | - Douglas J. Krause
- Antarctic Ecosystem Research Division, Southwest Fisheries Science Center, NOAA Fisheries, La Jolla, CA, United States of America
| | - Michael E. Goebel
- Ecology and Evolutionary Biology Department, University of California, Santa Cruz, Santa Cruz, CA, United States of America
| | - Joseph I. Hoffman
- Department of Animal Behaviour, University of Bielefeld, Bielefeld, Germany
- British Antarctic Survey, Cambridge, United Kingdom
| | - Eric A. Lewallen
- Department of Biological Sciences, Hampton University, Hampton, VA, United States of America
| | - Carolina A. Bonin
- Marine and Environmental Sciences Department, Hampton University, Hampton, VA, United States of America
- Department of Biological Sciences, Hampton University, Hampton, VA, United States of America
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Charapata P, Clark CT, Miller N, Kienle SS, Costa DP, Goebel ME, Gunn H, Sperou ES, Kanatous SB, Crocker DE, Borras-Chavez R, Trumble SJ. Whiskers provide time-series of toxic and essential trace elements, Se:Hg molar ratios, and stable isotope values of an apex Antarctic predator, the leopard seal. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 854:158651. [PMID: 36096211 DOI: 10.1016/j.scitotenv.2022.158651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 08/11/2022] [Accepted: 09/06/2022] [Indexed: 06/15/2023]
Abstract
In an era of rapid environmental change and increasing human presence, researchers need efficient tools for tracking contaminants to monitor the health of Antarctic flora and fauna. Here, we examined the utility of leopard seal whiskers as a biomonitoring tool that reconstructs time-series of significant ecological and physiological biomarkers. Leopard seals (Hydrurga leptonyx) are a sentinel species in the Western Antarctic Peninsula due to their apex predator status and top-down effects on several Antarctic species. However, there are few data on their contaminant loads. We analyzed leopard seal whiskers (n = 18 individuals, n = 981 segments) collected during 2018-2019 field seasons to acquire longitudinal profiles of non-essential (Hg, Pb, and Cd) and essential (Se, Cu, and Zn) trace elements, stable isotope (ẟ15N and ẟ13C) values and to assess Hg risk with Se:Hg molar ratios. Whiskers provided between 46 and 286 cumulative days of growth with a mean ~ 125 days per whisker (n = 18). Adult whiskers showed variability in non-essential trace elements over time that could partly be explained by changes in diet. Whisker Hg levels were insufficient (<20 ppm) to consider most seals being at "high" risk for Hg toxicity. Nevertheless, maximum Hg concentrations observed in this study were greater than that of leopard seal hair measured two decades ago. However, variation in the Se:Hg molar ratios over time suggest that Se may detoxify Hg burden in leopard seals. Overall, we provide evidence that the analysis of leopard seal whiskers allows for the reconstruction of time-series ecological and physiological data and can be valuable for opportunistically monitoring the health of the leopard seal population and their Antarctic ecosystem during climate change.
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Affiliation(s)
- Patrick Charapata
- Baylor University, Biology Department, Waco, TX, United States of America.
| | - Casey T Clark
- Washington Department of Fish and Wildlife, Marine Mammal Research Division, Olympia, WA, United States of America
| | - Nathan Miller
- Department of Geological Sciences, The University of Texas at Austin, Austin, TX, United States of America
| | - Sarah S Kienle
- Baylor University, Biology Department, Waco, TX, United States of America
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, The University of California at Santa Cruz, Santa Cruz, CA, United States of America
| | - Michael E Goebel
- Department of Ecology and Evolutionary Biology, The University of California at Santa Cruz, Santa Cruz, CA, United States of America; Antarctic Ecosystem Research Division, Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration (NOAA) Fisheries, La Jolla, CA, United States of America
| | - Heather Gunn
- Department of Geological Sciences, The University of Texas at Austin, Austin, TX, United States of America; Department of Earth and Environmental Sciences, Syracuse University, Syracuse, NY, United States of America
| | - Emily S Sperou
- Baylor University, Biology Department, Waco, TX, United States of America
| | - Shane B Kanatous
- Department of Biology, Colorado State University, Fort Collins, CO, United States of America
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA, United States of America
| | - Renato Borras-Chavez
- Center of Applied Ecology and Sustainability (CAPES), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Stephen J Trumble
- Baylor University, Biology Department, Waco, TX, United States of America
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Kienle SS, Friedlaender AS, Crocker DE, Mehta RS, Costa DP. Trade-offs between foraging reward and mortality risk drive sex-specific foraging strategies in sexually dimorphic northern elephant seals. ROYAL SOCIETY OPEN SCIENCE 2022; 9:210522. [PMID: 35116140 PMCID: PMC8767210 DOI: 10.1098/rsos.210522] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 12/14/2021] [Indexed: 05/04/2023]
Abstract
Sex-specific phenotypic differences are widespread throughout the animal kingdom. Reproductive advantages provided by trait differences come at a cost. Here, we link sex-specific foraging strategies to trade-offs between foraging reward and mortality risk in sexually dimorphic northern elephant seals (Mirounga angustirostris). We analyse a decadal dataset on movement patterns, dive behaviour, foraging success and mortality rates. Females are deep-diving predators in open ocean habitats. Males are shallow-diving benthic predators in continental shelf habitats. Males gain six times more mass and acquire energy 4.1 times faster than females. High foraging success comes with a high mortality rate. Males are six times more likely to die than females. These foraging strategies and trade-offs are related to different energy demands and life-history strategies. Males use a foraging strategy with a high mortality risk to attain large body sizes necessary to compete for females, as only a fraction of the largest males ever mate. Females use a foraging strategy with a lower mortality risk, maximizing reproductive success by pupping annually over a long lifespan. Our results highlight how sex-specific traits can drive disparity in mortality rates and expand species' niche space. Further, trade-offs between foraging rewards and mortality risk can differentially affect each sex's ability to maximize fitness.
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Affiliation(s)
- Sarah S. Kienle
- Ecology and Evolutionary Biology, University of California, 130 McAllister Way, Santa Cruz, CA 95060, USA
- Department of Biology, Baylor University, One Bear Place #97399, Waco, TX 76798, USA
| | - Ari S. Friedlaender
- Ocean Science, University of California, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Daniel E. Crocker
- Biology, Sonoma State University, 1801 East Cotati Avenue, Rohnert Park, CA 94928, USA
| | - Rita S. Mehta
- Ecology and Evolutionary Biology, University of California, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Daniel P. Costa
- Ecology and Evolutionary Biology, University of California, 130 McAllister Way, Santa Cruz, CA 95060, USA
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Complementary use of stable isotopes and fatty acids for quantitative diet estimation of sympatric predators, the Antarctic pack-ice seals. Oecologia 2021; 197:729-742. [PMID: 34626270 PMCID: PMC8585811 DOI: 10.1007/s00442-021-05045-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 09/20/2021] [Indexed: 11/18/2022]
Abstract
The quantitative use of stable isotopes (SIs) for trophic studies has seen a rapid growth whereas fatty acid (FA) studies remain mostly qualitative. We apply the Bayesian tool MixSIAR to both SI and FA data to estimate the diet of three sympatric predators: the crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii) and leopard seal (Hydrurga leptonyx). We used SI data of their vibrissae and FA data of their outer blubber to produce comparable diet estimates for the same individuals. Both SI and FA models predicted the same main diet components, although the predicted proportions differed. For the crabeater seal, both methods identified krill, Euphausia superba, as the main, and almost exclusive, food item, although the FA model estimated a slightly lower proportion, potentially due to the low lipid content of krill compared to the fish species used in the model. For the Weddell seal the FA model identified the fish Pleuragramma antarcticum as the most important prey, whereas the SI model was not able to distinguish among prey species, identifying a ‘fish-squid’ group as the main diet component. For the leopard seal, both models identified krill as the main contributor; however, the predicted proportions for the secondary sources differed. Although vibrissae and outer blubber may not represent the same timeframe, the use of MixSIAR with FA data provides diet estimates comparable to those obtained with SI data, thus, both approaches were complimentary. The use of both biotracers offers a feasible option to study diets of wild animals in a quantitative manner.
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