Potential population-level effects of increased haulout-related mortality of Pacific walrus calves

Polar Biology
By: , and 



Availability of summer sea ice has been decreasing in the Chukchi Sea during recent decades, and increasing numbers of Pacific walruses have begun using coastal haulouts in late summer during years when sea ice retreats beyond the continental shelf. Calves and yearlings are particularly susceptible to being crushed during disturbance events that cause the herd to panic and stampede at these large haulouts, but the potential population-level effects of this mortality are unknown. We used recent harvest data, along with previous assumptions about demographic parameters for this population, to estimate female population size and structure in 2009 and project these numbers forward using a range of assumptions about future harvests and haulout-related mortality that might result from increased use of coastal haulouts during late summer. We found that if demographic parameters were held constant, the levels of harvest that occurred during 1990–2008 would have allowed the population to grow during that period. Our projections indicate, however, that an increase in haulout-related mortality affecting only calves has a greater effect on the population than an equivalent increase in harvest-related mortality distributed among all age classes. Therefore, disturbance-related mortality of calves at coastal haulouts may have relatively important population consequences.
Publication type Article
Publication Subtype Journal Article
Title Potential population-level effects of increased haulout-related mortality of Pacific walrus calves
Series title Polar Biology
DOI 10.1007/s00300-012-1259-3
Volume 36
Issue 2
Year Published 2013
Language English
Publisher Springer
Publisher location Reston, VA
Contributing office(s) Alaska Science Center Biology
Description 8 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Polar Biology
First page 291
Last page 298
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