Spatial and temporal variation in sea otter demography

By: , and 
Edited by: M. Tim TinkerJames A. EstesKatherine RallsTerrie M. WilliamsDavid A. Jessup, and Daniel P. Costa



1) Better information on historical and current population dynamics is central to understanding patterns of growth and decline in the California sea otter population. We developed a maximum likelihood-based analytical method to estimate historical age/sex specific vital rates as well as spatial and temporal variation in vital rates from longitudinal databases on population census numbers and the age-structure of salvaged carcasses.

2) We estimated current demographic parameters by conducting a mark-recapture study, measuring survival and reproduction of 115 radio-tagged individuals between 2001 and 2004. These current estimates were compared to estimates from a similar study of radiotagged otters conducted in the mid-eighties.

3) Together, these two approaches indicated that survival has decreased substantially between the early 1990s and the present and is lowest in the north-central portion of the population's range.

4) The greatest decrease in survival was for adult females (≥ 4 years of age). Variation in the survival of this age/sex class is primarily responsible for regulating population growth and driving population trends.

Publication type Book chapter
Publication Subtype Book Chapter
Title Spatial and temporal variation in sea otter demography
Chapter 2
Year Published 2006
Language English
Publisher U.S. Department of the Interior: Minerals Management Service, Pacific OCS Region
Contributing office(s) Alaska Science Center
Description 31 p.
Larger Work Type Report
Larger Work Subtype Federal Government Series
Larger Work Title Population dynamics and biology of the California sea otter (Enhydra lutris nereis) at the southern end of its range
First page 12
Last page 42
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