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Crawford SG, Coker RH, O’Hara TM, Breed GA, Gelatt T, Fadely B, Burkanov V, Rivera PM, Rea LD. Fasting durations of Steller sea lion pups vary among subpopulations-evidence from two plasma metabolites. CONSERVATION PHYSIOLOGY 2023; 11:coad084. [PMID: 38026798 PMCID: PMC10673819 DOI: 10.1093/conphys/coad084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 08/28/2023] [Accepted: 10/16/2023] [Indexed: 12/01/2023]
Abstract
Geographic differences in population growth trends are well-documented in Steller sea lions (Eumetopias jubatus), a species of North Pacific pinniped listed under the U.S. Endangered Species Act in 1990 following a marked decline in population abundance that began during the 1970s. As population growth is intrinsically linked to pup production and survival, examining factors related to pup physiological condition provides useful information to management authorities regarding potential drivers of regional differences. During dam foraging trips, pups predictably transition among three fasting phases, distinguished by the changes in the predominant metabolic byproduct. We used standardized ranges of two plasma metabolites (blood urea nitrogen and β-hydroxybutyrate) to assign pups to fasting categories (n = 1528, 1990-2016, 12 subpopulations): Recently Fed-Phase I (digestion/assimilation-expected hepatic/muscle glycogen usage), Phase II (expected lipid utilization), transitioning between Phases II-III (expected lipid utilization with increased protein reliance), or Phase III (expected protein catabolism). As anticipated, the majority of pups were classified as Recently Fed-Phase I (overall mean proportion = 0.72) and few pups as Phase III (overall mean proportion = 0.04). By further comparing pups in Short (Recently Fed-Phase II) and Long (all other pups) duration fasts, we identified three subpopulations with significantly (P < 0.03) greater proportions of pups dependent upon endogenous sources of energy for extended periods, during a life stage of somatic growth and development: the 1) central (0.27 ± 0.09) and 2) western (0.36 ± 0.13) Aleutian Island (declining population trend) and 3) southern Southeast Alaska (0.32 ± 0.06; increasing population trend) subpopulations had greater Long fast proportions than the eastern Aleutian Islands (0.10 ± 0.05; stabilized population). Due to contrasting population growth trends among these highlighted subpopulations over the past 50+ years, both density-independent and density-dependent factors likely influence the dam foraging trip duration, contributing to longer fasting durations for pups at some rookeries.
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Affiliation(s)
- Stephanie G Crawford
- Department of Biology and Wildlife and Institute of Northern Engineering, University of Alaska Fairbanks, 1764 Tanana Loop, Fairbanks, Alaska 99775, USA
| | - Robert H Coker
- Montana Center for Work Physiology and Exercise Metabolism, University of Montana, 32 Campus Drive, Missoula, Montana 59812, USA
| | - Todd M O’Hara
- Veterinary Integrative Biosciences, School of Veterinary Medicine & Biomedical Sciences, Texas A&M University, 402 Raymond Stotzer Parkway, Bldg 2, College Station, Texas 77843, USA
| | - Greg A Breed
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA
| | - Tom Gelatt
- Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way N.E., Bldg. 4, Seattle, Washington 98115, USA
| | - Brian Fadely
- Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way N.E., Bldg. 4, Seattle, Washington 98115, USA
| | - Vladimir Burkanov
- Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way N.E., Bldg. 4, Seattle, Washington 98115, USA
| | - Patricia M Rivera
- Center for Alaska Native Health Research, Institute of Arctic Biology, University of Alaska Fairbanks, 2141 Koyukuk Drive, Fairbanks, Alaska 99775, USA
| | - Lorrie D Rea
- Institute of Northern Engineering, University of Alaska Fairbanks, 1764 Tanana Loop, Fairbanks, Alaska 99775, USA
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Hastings KK, Jemison LA, Pendleton GW, Johnson DS, Gelatt TS. Age-specific reproduction in female Steller sea lions in Southeast Alaska. Ecol Evol 2023; 13:e10515. [PMID: 37780535 PMCID: PMC10533480 DOI: 10.1002/ece3.10515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Revised: 08/04/2023] [Accepted: 08/23/2023] [Indexed: 10/03/2023] Open
Abstract
Age-, region-, and year-specific estimates of reproduction are needed for monitoring wildlife populations during periods of ecosystem change. Population dynamics of Steller sea lions (Eumetopias jubatus) in Southeast Alaska varied regionally (with high population growth and survival in the north vs. the south) and annually (with reduced adult female survival observed following a severe marine heatwave event), but reproductive performance is currently unknown. We used mark-resighting data from 1006 Steller sea lion females marked as pups at ~3 weeks of age from 1994 to 1995 and from 2001 to 2005 and resighted from 2002 to 2019 (to a maximum age of 25) to examine age-, region-, and year-specific reproduction. In the north versus the south, age of first reproduction was earlier (beginning at age 4 vs. age 5, respectively) but annual birth probabilities of parous females were reduced by 0.05. In an average year pre-heatwave, the proportion of females with pup at the end of the pupping season peaked at ages 12-13 with ~0.60/0.65 (north/south) with pup, ~0.30/0.25 with juvenile, and ~0.10 (both regions) without a dependent. In both regions, reproductive senescence was gradual after age 12: ~0.40, 0.40, and 0.20 of females were in these reproductive states, respectively, by age 20. Correcting for neonatal mortality, true birth probabilities at peak ages were 0.66/0.72 (north/south). No cost of reproduction on female survival was detected, but pup production remained lower (-0.06) after the heatwave event, which if sustained could result in population decline in the south. Reduced pup production and greater retention of juveniles during periods of poor prey conditions may be an important strategy for Steller sea lions in Southeast Alaska, where fine-tuning reproduction based on nutritional status may improve the lifetime probability of producing pups under good conditions in a variable and less productive environment.
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Affiliation(s)
| | | | | | - Devin S. Johnson
- Protected Resources Division, National Marine Fisheries ServicePacific Islands Fisheries Science CenterHonoluluHawaiiUSA
| | - Thomas S. Gelatt
- Marine Mammal Laboratory, National Marine Fisheries ServiceAlaska Fisheries Science CenterSeattleWashingtonUSA
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Avery J, Zinn S. Extraordinary diversity of the pinniped lactation triad: lactation and growth strategies of seals, sea lions, fur seals, and walruses. Anim Front 2023; 13:86-95. [PMID: 37324205 PMCID: PMC10266754 DOI: 10.1093/af/vfad037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023] Open
Affiliation(s)
| | - Steven A Zinn
- Department of Animal Science, University of Connecticut, Storrs, CT 06269, USA
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Warlick AJ, Johnson DS, Gelatt TS, Converse SJ. Environmental drivers of demography and potential factors limiting the recovery of an endangered marine top predator. Ecosphere 2022. [DOI: 10.1002/ecs2.4325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- Amanda J. Warlick
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington USA
| | - Devin S. Johnson
- Pacific Islands Fisheries Science Center National Marine Fisheries Service Honolulu Hawaii USA
| | - Tom S. Gelatt
- Marine Mammal Laboratory Alaska Fisheries Science Center, National Marine Fisheries Service Seattle Washington USA
| | - Sarah J. Converse
- U.S. Geological Survey, Washington Cooperative Fish and Wildlife Research Unit, School of Environmental and Forest Sciences & School of Aquatic and Fishery Sciences University of Washington Seattle Washington USA
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