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Age-specific reproduction in female Steller sea lions in Southeast Alaska.

Authors
  • Hastings, Kelly K1
  • Jemison, Lauri A1
  • Pendleton, Grey W1
  • Johnson, Devin S2
  • Gelatt, Thomas S3
  • 1 Alaska Department of Fish and Game Juneau Alaska USA.
  • 2 Protected Resources Division, National Marine Fisheries Service Pacific Islands Fisheries Science Center Honolulu Hawaii USA.
  • 3 Marine Mammal Laboratory, National Marine Fisheries Service Alaska Fisheries Science Center Seattle Washington USA.
Type
Published Article
Journal
Ecology and Evolution
Publisher
Wiley (John Wiley & Sons)
Publication Date
Sep 01, 2023
Volume
13
Issue
9
Identifiers
DOI: 10.1002/ece3.10515
PMID: 37780535
Source
Medline
Keywords
Language
English
License
Unknown

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. © 2023 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

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