Potential population-level effects of increased haulout-related mortality of Pacific walrus calves
Return to Arctic Science for Decisions Home
Full Publication: https://doi.org/10.1007/s00300-012-1259-3Product Type: Journal Article
Year: 2013
Authors: Udevitz, M. S., R. L. Taylor, J. L. Garlich-Miller, L. T. Quakenbush, and J. A. Snyder
Suggested Citation:
Udevitz, M. S., R. L. Taylor, J. L. Garlich-Miller, L. T. Quakenbush, and J. A. Snyder. 2013. Potential population-level effects of increased haulout-related mortality of Pacific walrus calves. Polar Biology 36(2):291-298. doi:10.1007/s00300-012-1259-3
Abstract
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.
Keywords: Pacific walrus, haulout, mortality, population dynamics, trampling
Annotation
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. Disturbance-related mortality of calves at coastal haulouts may have relatively important population consequences, which is especially important to consider in terms of the potential disturbance effects of anthropogenic activities.