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Oecologia

, Volume 134, Issue 3, pp 343–349 | Cite as

Habitat-specific demography: evidence for source-sink population structure in a mammal, the pika

  • M. P. KreuzerJr.Email author
  • N. J. Huntly
Population Ecology

Abstract

Theory suggests that populations may persist in sink habitats that cannot support replacement-level birth rates. Although it is commonly believed that organisms that can actively select habitat should rarely occur in sinks, the frequency of use of sinks in free-ranging species is not well-documented. We found that a population of American pikas (Ochotona princeps, Lagomorpha) inhabiting distinct alpine habitats (meadow and snowbed) in Wyoming, USA, had habitat-specific demographic rates that produced a source-sink population structure. Population size increased in both habitats in summer and declined in both habitats in winter, with populations in snowbeds increasing more during summer and decreasing more over winter. Birth rates were consistently higher in meadows and populations in meadows had a consistently higher finite rate of increase (λ, from life tables) than did those in snowbeds, for which λ was far below that needed for replacement. Patterns of immigration, population structure, and temporal variation in population size were as expected if meadows were functional sources and snowbeds functional sinks. Patterns of snowmelt differed between habitats, predicted the critical difference in birth rates between habitats, and are a likely primary cause of the differences in habitat-specific birth rates that we observed. This study provides a clear example of source-sink population structure for a mammal.

Keywords

Habitat use Niche Ochotona princeps Population dynamics 

Notes

Acknowledgements

We thank J Roach, F Stevens, WC Witt, J Kreuzer, D Gentry, S Relyea, A Ray, and M Sanford for help with fieldwork, R van Kirk and T Peterson for mathematical and statistical advice, and the National Science Foundation (DEB 9972608), the American Society of Mammalogists, the Graduate Student Research and Scholarship Committee at Idaho State University, and the NERC Centre for Population Biology (UK) for support. All work followed guidelines for study and use of mammals as set forth by the American Society of Mammalogists and United States Department of Agriculture and was approved by the Idaho State University IACUC.

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Department of Biological Sciences and Center for Ecological Research and EducationIdaho State UniversityPocatelloUSA

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