Demography of the Pacific walrus (Odobenus rosmarus divergens) in a changing Arctic

Marine Mammal Science
By: , and 



The Pacific walrus (Odobenus rosmarus divergens) is a candidate to be listed as an endangered species under United States law, in part, because of climate change‐related concerns. While the population was known to be declining in the 1980s and 1990s, its recent status has not been determined. We developed Bayesian models of walrus population dynamics to assess the population by synthesizing information on population sizes, age structures, reproductive rates, and harvests for 1974–2015. Candidate models allowed for temporal variation in some or all vital rates, as well as density dependence or density independence in reproduction and calf survival. All selected models indicated that the population underwent a multidecade decline, which began moderating in the 1990s, and that annual reproductive rate and natural calf survival rates rose over time in a density‐dependent manner. However, selected models were equivocal regarding whether the natural juvenile survival rate was constant or decreasing over time. Depending on whether juvenile survival decreased after 1998, the population growth rate either increased during 1999–2015 or stabilized at a lesser level of decline than seen in the 1980s. The probability that the population was still declining in 2015 ranged from 45% to 87%.

Publication type Article
Publication Subtype Journal Article
Title Demography of the Pacific walrus (Odobenus rosmarus divergens) in a changing Arctic
Series title Marine Mammal Science
DOI 10.1111/mms.12434
Volume 34
Issue 1
Year Published 2018
Language English
Publisher Wiley
Contributing office(s) Alaska Science Center Biology MFEB, Advanced Research Computing (ARC)
Description 33 p.
First page 54
Last page 86
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