Population fluctuations in the small mammals of the Kluane Region, Yukon Territory

Abstract

From 1973 to 1977 we studied popUlation changes in small rodents of the Kluane Lake region, southwestern Yukon. Six species were at maximal abundance in 1973 and were relatively scarce from 1974 to 1977. Only one species, Microtus oeconomus (Tundra Vole). showed a correlation between body size and popUlation size (the Chitty Effect). Reproductive rates varied among species but were not related to popUlation density in any species. Peromyscus maniculatus (Deer Mouse) had the lowest reproductive rate because of a short breeding season, so that females had only one or two litters in most years. There was no evidence of winter breeding in any species. We conclude that none of the small rodent species in the Kluane region, except Microtus oeconomus, show good evidence of 3-4 year population cycles. Density fluctuations are irregular and popUlations appear to be strongly r-selected in an unfavourable environment which is typically almost empty of rodents.