Factors influencing Soay sheep survival

Catchpole, Edward A. and Morgan, Byron J. T. and Coulson, Tim and Freeman, Stephen N. and Albon, Steve D. (2000) Factors influencing Soay sheep survival. Journal of the Royal Statistical Society: Series C (Applied Statistics), 49 . pp. 453-472. ISSN 0035-9254. (The full text of this publication is not available from this repository)

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Official URL
http://dx.doi.org/10.1111/1467-9876.00205

Abstract

We present a survival analysis of Soay sheep mark recapture and recovery data. Unlike previous conditional analyses, it is not necessary to assume equality of recovery and recapture probabilities; instead these are estimated by maximum likelihood. Male and female sheep are treated separately, with the higher numbers and survival probabilities of the females resulting in a more complex model than that used for the males. In both cases, however, age and time aspects need to be included and there is a strong indication of a reduction in survival for sheep aged 7 years or more. Time variation in survival is related to the size of the population and selected weather variables, by using logistic regression. The size of the population significantly affects the survival probabilities of male and female lambs, and of female sheep aged 7 or more years. March rainfall and a measure of the North Atlantic oscillation are found to influence survival significantly for all age groups considered, for both males and females. Either of these weather variables can be used in a model. Several phenotypic and genotypic individual covariates are also fitted. The only covariate which is found to influence survival significantly is the type of horn of first-year female sheep. There is a substantial variation in the recovery probabilities over time, reflecting in part the increased effort when a population crash was expected. The goodness of fit of the model is checked by using graphical procedures.

Item Type: Article
Uncontrolled keywords: integrated analysis; logistic regression; mark recapture; mark recovery; maximum likelihood; Soay sheep; survival
Subjects: H Social Sciences > HA Statistics
Divisions: Faculties > Science Technology and Medical Studies > School of Mathematics Statistics and Actuarial Science > Statistics
Depositing User: P. Ogbuji
Date Deposited: 06 Apr 2009 08:18
Last Modified: 13 Jun 2014 10:20
Resource URI: http://kar.kent.ac.uk/id/eprint/16246 (The current URI for this page, for reference purposes)
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