[MARMAM] New paper on walrus demography

Taylor, Rebecca rebeccataylor at usgs.gov
Fri Sep 22 09:46:57 PDT 2017

Dear MARMAM community,

My coathors and I are pleased to announce a new publication on walrus
demography.  It is entitled "Demography of the Pacific walrus (
*Odobenus rosmarus divergens*) in a changing Arctic," and is available on
early view through Marine Mammal Science (
http://onlinelibrary.wiley.com/doi/10.1111/mms.12434/abstract ).  If for
any reason you cannot access it online, feel free to email me for a copy of
the paper at rebeccataylor at usgs.gov .


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%.
Taylor, R. L., Udevitz, M. S., Jay, C. V., Citta, J. J., Quakenbush, L. T.,
Lemons, P. R., Snyder, J. A., 2017. Demography of the Pacific walrus (*Odobenus
rosmarus divergens*) in a changing Arctic.  Marine Mammal Science. DOI: 10.


Rebecca Taylor

Rebecca Taylor
Research Statistician
USGS Alaska Science Center
4210 University Drive
Anchorage, AK 99508
rebeccataylor at usgs.gov
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