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Investigating life-history traits of Steller sea lions with multistate hidden Markov mark–recapture models: Age at weaning and body size effects
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2021
Source: Ecology and Evolution, 11(2), 714-734
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Journal Title:Ecology and Evolution
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Description:The duration of offspring care is critical to female fitness and population resilience by allowing flexibility in life‐history strategies in a variable environment. Yet, for many mammals capable of extended periods of maternal care, estimates of the duration of offspring dependency are not available and the relative importance of flexibility of this trait on fitness and population viability has rarely been examined. We used data from 4,447 Steller sea lions Eumetopias jubatus from the Gulf of Alaska and multistate hidden Markov mark–recapture models to estimate age‐specific weaning probabilities. Maternal care beyond age 1 was common: Weaning was later for animals from Southeast Alaska (SEAK) and Prince William Sound (PWS, weaning probabilities: 0.536–0.648/0.784–0.873 by age 1/2) compared with animals born to the west (0.714–0.855/0.798–0.938). SEAK/PWS animals were also smaller than those born farther west, suggesting a possible link. Females weaned slightly earlier (+0.080 at age 1 and 2) compared with males in SEAK only. Poor survival for weaned versus unweaned yearlings occurred in southern SEAK (female survival probabilities: 0.609 vs. 0.792) and the central Gulf (0.667 vs. 0.901), suggesting poor conditions for juveniles in these areas. First‐year survival increased with neonatal body mass (NBM) linearly in the Gulf and nonlinearly in SEAK. The probability of weaning at age 1 increased linearly with NBM for SEAK animals only. Rookeries where juveniles weaned at earlier ages had lower adult female survival, but age at weaning was unrelated to population trends. Our results suggest the time to weaning may be optimized for different habitats based on long‐term average conditions (e.g., prey dynamics), that may also shape body size, with limited short‐term plasticity. An apparent trade‐off of adult survival in favor of juvenile survival and large offspring size in the endangered Gulf of Alaska population requires further study.
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Content Notes:This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
Data are available in the Dryad Digital Repository
Funding for this study was provided to the ADFG by the State of Alaska and by the National Oceanic and Atmospheric Administration NOAA/NMFS.
The NOAA/NMFS additionally provided funding to the MML. This research was approved by the Institutional Animal Care and Use Committees and under permits issued by the NMFS to the ADFG and the MML. Permits were additionally granted by the U.S. National Park Service, the U. S. Fish and Wildlife Service–Alaska Maritime National Wildlife Refuge, and the Department of Fisheries and Oceans Canada.
Research by the MML was conducted under permits; research by the ADFG was conducted under permits. The findings and conclusions in this paper are those of the author(s) and do not necessarily represent the views of the NMFS,
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Source:Ecology and Evolution, 11(2), 714-734
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Rights Information:CC BY
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Compliance:Submitted
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