Climate influences on female survival in a declining population of southern elephant seals (Mirounga leonina)

Abstract The Southern Ocean has been disproportionately affected by climate change and is therefore an ideal place to study the influence of changing environmental conditions on ecosystems. Changes in the demography of predator populations are indicators of broader shifts in food web structure, but...

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Bibliographic Details
Published in:Ecology and Evolution
Main Authors: Sophia Volzke, Clive R. McMahon, Mark A. Hindell, Harry R. Burton, Simon J. Wotherspoon
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2021
Subjects:
capture‐mark‐recapture studies
demographics
ecological modeling
El Niño Southern Oscillation
Hidden Markov Model
population dynamics
Ecology
QH540-549.5
Antarctic
Southern Ocean
Soi
Antarc*
Elephant Seals
Macquarie Island
Mirounga leonina
Sea ice
Southern Elephant Seals
Online Access:https://doi.org/10.1002/ece3.7919
https://doaj.org/article/06e319240c904d77976fd69791926774
Description
Summary:Abstract The Southern Ocean has been disproportionately affected by climate change and is therefore an ideal place to study the influence of changing environmental conditions on ecosystems. Changes in the demography of predator populations are indicators of broader shifts in food web structure, but long‐term data are required to study these effects. Southern elephant seals (Mirounga leonina) from Macquarie Island have consistently decreased in population size while all other major populations across the Southern Ocean have recently stabilized or are increasing. Two long‐term mark‐recapture studies (1956–1967 and 1993–2009) have monitored this population, which provides an opportunity to investigate demographic performance over a range of climatic conditions. Using a 9‐state matrix population model, we estimated climate influences on female survival by incorporating two major climatic indices into our model: The Southern Annular Mode (SAM) and the Southern Oscillation Index (SOI). Our best model included a 1 year lagged effect of SAM and an unlagged SOI as covariates. A positive relationship with SAM1 (lagged) related the previous year's SAM with juvenile survival, potentially due to changes in local prey availability surrounding Macquarie Island. The unlagged SOI had a negative effect on both juvenile and adult seals, indicating that sea ice dynamics and access to foraging grounds on the East Antarctic continental shelf could explain the different contributions of ENSO events on the survival of females in this population.

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