Demographic analysis of a declining pika Ochotona collaris population: linking survival to broad-scale climate patterns via spring snowmelt patterns
Article first published online: 19 JUL 2007
Journal of Animal Ecology
Volume 76, Issue 5, pages 899–907, September 2007
How to Cite
MORRISON, S. F. and HIK, D. S. (2007), Demographic analysis of a declining pika Ochotona collaris population: linking survival to broad-scale climate patterns via spring snowmelt patterns. Journal of Animal Ecology, 76: 899–907. doi: 10.1111/j.1365-2656.2007.01276.x
- Issue published online: 19 JUL 2007
- Article first published online: 19 JUL 2007
- Received 1 March 2007; accepted 25 May 2007 ; Handling Editor: Graeme Hays
- collared pika;
- life-table response experiment;
- Pacific Decadal Oscillation;
- 1Demographic analysis is essential in order to determine which factors, such as survival, fertility and other life-history characteristics, have the greatest influence on a population's rate of growth (λ).
- 2We used life-table response experiments (LTREs) to assess the relative importance of survival and fertility rates for an alpine lagomorph, the collared pika Ochotona collaris, using 12 years (1995–2006) of census data. The LTRE analysis was repeated for each of three subpopulations within the main study site that were defined by aspect (east, west and south).
- 3Across the entire study site, the survival and fertility of adults contributed 35·6 and 43·5%, respectively, to the variance observed in the projected population growth rate, V(λ), whereas juvenile survival contributed 20·9%. Adult survival and fertility contributed approximately equal amounts for each subpopulation when considered separately, although their rank order varied spatially.
- 4Adult survival across the entire site was positively correlated to the Pacific Decadal Oscillation (PDO) with a time lag of 1 year, and was uncorrelated to adult density. The PDO was negatively correlated to the timing of spring snowmelt at our site, implicating the importance of earlier spring conditions and plant phenology on the subsequent winter survival of adults and therefore, population growth.
- 5When subpopulations were analysed separately, survivals and fertilities were variously correlated to lagged PDO and adult densities, but the patterns varied spatially. Therefore, the mechanisms underlying V(λ) can vary substantially over relatively short distances.