Effects of habitat quality on growth, age of first reproduction, and dispersal in Gunnison's prairie dogs (Cynomys gunnisoni)

Abstract

Populations of the highly social Gunnison's prairie dog (Cynomys gunnisoni) were studied at two sites in south central Colorado. The sites differed in availability of water, duration of the growing season, and the diversity and quantity of edible vegetation. At the lusher site, Quartz Creek, all age- and sex classes weighed significantly more than their counterparts at the more barren site, Blue Mesa. Growth rates and overwinter survival of Quartz Creek young were higher than at Blue Mesa. Two of 5 yearling females raised litters at Quartz Creek, whereas none of 15 yearling females weaned litters at Blue Mesa. Quartz Creek females produced larger litters [Formula: see text] than Blue Mesa females [Formula: see text]. At Quartz Creek, 6 of 17 yearlings dispersed from their natal harem, but none of the 31 yearlings at Blue Mesa dispersed. Thus, in a favorable habitat, Gunnison's prairie dogs were heavier, reached sexual maturity more rapidly, and dispersed at a younger age than in a less favorable habitat. These results provide intraspecific support for Armitage's hypothesis that delayed sexual maturity and dispersal in the large-bodied, social ground squirrels is associated with the age at which immatures attain adult weight.