Document: MIC-3-51-23

Evidence for benefits to occupants of sink habitats.

KREUZER, JR., M.* and N.J.HUNTLY

Idaho State University, Pocatello, ID 83209, USA ¹

Abstract:
Although it is clear that animals depend on a variety of habitats, reasons for occupation of low-quality habitats remain controversial. We hypothesize three ways in which individuals may benefit: 1) Low-quality habitat temporarily supports juveniles that subsequently reside in higher-quality habitat, 2) low-quality habitat supports males that mate with female residents of nearby higher-quality areas, or 3) habitats vary in relative quality across years. We tested these hypotheses with three years of demographic data from American pika (Ochotona princeps) populations occupying different microhabitats in the Beartooth Mountains of Wyoming. The three-year average of adult density was slightly higher in Lush habitats, but population growth rates were much higher in Lush habitats than in Sparse habitats, and the latter appeared to be population sinks. Sink habitats contained mostly juveniles; the adult population in sinks was mostly male. Overwinter population losses of juveniles were much higher in sinks, with a potentially large loss to dispersal. There was no difference in the disappearance rate of adults. Body weight did not differ between habitats or with population density. We found no year by habitat interaction in population density, birth rate, or body weight indicating that temporal heterogeneity may not be a factor. We found some support for the refuge hypothesis, and little for the satellite breeder hypothesis. Further data are needed to adequately differentiate between these three hypotheses for this population.

Keywords: Source-sink dynamics, habitat quality

This abstract is being presented at: 9:30 AM in session:
Oral Session #21: Small Mammal Population Ecology.