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Factors influencing Soay sheep survival

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  • E. A. Catchpole
  • B. J. T. Morgan
  • T. N. Coulson
  • S. N. Freeman
  • S. D. Albon

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.

Suggested Citation

  • E. A. Catchpole & B. J. T. Morgan & T. N. Coulson & S. N. Freeman & S. D. Albon, 2000. "Factors influencing Soay sheep survival," Journal of the Royal Statistical Society Series C, Royal Statistical Society, vol. 49(4), pages 453-472.
    • Handle: RePEc:bla:jorssc:v:49:y:2000:i:4:p:453-472
    DOI: 10.1111/1467-9876.00205
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    Citations

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    Cited by:

    1. R. King & S. P. Brooks, 2002. "Model Selection for Integrated Recovery/Recapture Data," Biometrics, The International Biometric Society, vol. 58(4), pages 841-851, December.
    2. R. King & S. P. Brooks & B. J. T. Morgan & T. Coulson, 2006. "Factors Influencing Soay Sheep Survival: A Bayesian Analysis," Biometrics, The International Biometric Society, vol. 62(1), pages 211-220, March.
    3. R. King & S. P. Brooks & T. Coulson, 2008. "Analyzing Complex Capture–Recapture Data in the Presence of Individual and Temporal Covariates and Model Uncertainty," Biometrics, The International Biometric Society, vol. 64(4), pages 1187-1195, December.
    4. Besbeas, P.T. & McCrea, R.S. & Morgan, B.J.T., 2022. "Selecting age structure in integrated population models," Ecological Modelling, Elsevier, vol. 473(C).
    5. Texeira, Marcos & Paruelo, Jose M., 2006. "Demography, population dynamics and sustainability of the Patagonian sheep flocks," Agricultural Systems, Elsevier, vol. 87(2), pages 123-146, February.
    6. Diana J. Cole, 2019. "Parameter redundancy and identifiability in hidden Markov models," METRON, Springer;Sapienza Università di Roma, vol. 77(2), pages 105-118, August.
    7. Anne Loison & Bernt-Erik Sæther & Kurt Jerstad & Ole Wiggo Røstad, 2002. "Disentangling the sources of variation in the survival of the European dipper," Journal of Applied Statistics, Taylor & Francis Journals, vol. 29(1-4), pages 289-304.
    8. Ling, Stephen & Milner-Gulland, E.J., 2008. "Developing an artificial ecology for use as a strategic management tool: A case study of ibex hunting in the North Tien Shan," Ecological Modelling, Elsevier, vol. 210(1), pages 15-36.
    9. P. Besbeas & S. N. Freeman & B. J. T. Morgan & E. A. Catchpole, 2002. "Integrating Mark–Recapture–Recovery and Census Data to Estimate Animal Abundance and Demographic Parameters," Biometrics, The International Biometric Society, vol. 58(3), pages 540-547, September.
    10. Texeira, Marcos & Paruelo, José M. & Jobbagy, Esteban, 2008. "How do forage availability and climate control sheep reproductive performance?," Ecological Modelling, Elsevier, vol. 217(1), pages 197-206.
    11. S. C. Barry & S. P. Brooks & E. A. Catchpole & B. J. T. Morgan, 2003. "The Analysis of Ring-Recovery Data Using Random Effects," Biometrics, The International Biometric Society, vol. 59(1), pages 54-65, March.
    12. George Seber & Carl Schwarz, 2002. "Capture-recapture: Before and after EURING 2000," Journal of Applied Statistics, Taylor & Francis Journals, vol. 29(1-4), pages 5-18.
    13. S. A. Sisson & Y. Fan, 2009. "Towards automating model selection for a mark–recapture–recovery analysis," Journal of the Royal Statistical Society Series C, Royal Statistical Society, vol. 58(2), pages 247-266, May.
    14. S. P. Brooks & E. A. Catchpole & B. J. T. Morgan & M. P. Harris, 2002. "Bayesian methods for analysing ringing data," Journal of Applied Statistics, Taylor & Francis Journals, vol. 29(1-4), pages 187-206.

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