Skip to main content
U.S. flag

An official website of the United States government

Incorporating diverse data and realistic complexity into demographic estimation procedures for sea otters

January 1, 2006

Reliable information on historical and current population dynamics is central to understanding patterns of growth and decline in animal populations. We developed a maximum likelihood-based analysis to estimate spatial and temporal trends in age/sex-specific survival rates for the threatened southern sea otter (Enhydra lutris nereis), using annual population censuses and the age structure of salvaged carcass collections. We evaluated a wide range of possible spatial and temporal effects and used model averaging to incorporate model uncertainty into the resulting estimates of key vital rates and their variances. We compared these results to current demographic parameters estimated in a telemetry-based study conducted between 2001 and 2004. These results show that survival has decreased substantially from the early 1990s to the present and is generally lowest in the north-central portion of the population's range. The greatest temporal decrease in survival was for adult females, and variation in the survival of this age/sex class is primarily responsible for regulating population growth and driving population trends. Our results can be used to focus future research on southern sea otters by highlighting the life history stages and mortality factors most relevant to conservation. More broadly, we have illustrated how the powerful and relatively straightforward tools of information-theoretic-based model fitting can be used to sort through and parameterize quite complex demographic modeling frameworks. ?? 2006 by the Ecological Society of America.

Citation Information

Publication Year 2006
Title Incorporating diverse data and realistic complexity into demographic estimation procedures for sea otters
DOI 10.1890/1051-0761(2006)016[2293:IDDARC]2.0.CO;2
Authors M. Timothy Tinker, Daniel F. Doak, James A. Estes, Brian B. Hatfield, Michelle M. Staedler, Arthur Gross
Publication Type Article
Publication Subtype Journal Article
Series Title Ecological Applications
Series Number
Index ID 70028722
Record Source USGS Publications Warehouse
USGS Organization Alaska Science Center