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A NONINVASIVE DEMOGRAPHIC ASSESSMENT OF SEA LIONS BASED ON STAGE‐SPECIFIC ABUNDANCES
Author(s) -
Wielgus Jeffrey,
Gonzalez-Suarez Manuela,
Aurioles-Gamboa David,
Gerber Leah R.
Publication year - 2008
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/07-0892.1
Subject(s) - sea lion , abundance (ecology) , zalophus californianus , vital rates , ecology , population , estimation , overexploitation , biology , statistics , population growth , econometrics , geography , demography , mathematics , economics , management , sociology
A pressing need exists to develop new approaches for obtaining information on demographic rates without causing further threats to imperiled animal populations. In this paper, we illustrate and apply a data‐fitting technique based on quadratic programming that uses stage‐specific abundance data to estimate demographic rates and asymptotic population growth rates (λ). We used data from seven breeding colonies of California sea lions ( Zalophus californianus ) in the Gulf of California, Mexico. Estimates of λ were similar to those from previous studies relying on a diffusion approximation using trends in total abundance. On average, predicted abundances were within 24% of the observed value for the inverse estimation method and within 29% of the observed value for the diffusion approximation. Our results suggest that three of the seven populations are declining (λ < 1), but as many as six may be at risk. Elasticity and sensitivity analyses suggest that population management in most sites should focus on the protection of adults, whose survival generally contributes the most to λ. The quadratic programming approach is a promising noninvasive technique for estimating demographic rates and assessing the viability of populations of imperiled species.