A Population of Great Basin Pocket Mice, Perognathus parvus, in the Shrub-Steppe of South-Central Washington

摘要: A population of Great Basin pocket mice, Perognathus parvus, was live-trapped in 1967-72 on a 2.7-ha study area south-central Washington to determine their density, reproductive performance, longevity, movements, and home range, as well functional role northern shrub-steppe habitat. During 41,310 trap-nights we captured 15,386 mice representing seven species: Peromyscus maniculatus, Onychomys leuco- gaster, Reithrodontomys megalotis, Lagurus curtatus, Microtus montanus, Sylvilagus nut- tallii. Pocket accounted for 91%, deer 8%, the remaining species only 1% captures. Most remained inactive underground between December February. Adult e became trappable at an average date 26 March; 9 emerged about 18 April. Once active, adults 60 days years average-to-excellent food production, 90 poor production. Sex ratios animals differed significantly from 1:1 half sampling periods, usually favored adult . Males had scrotal testes 4 mo, with highest proportion The first signs estrus were observed April, palpable pregnancies May, last pregnant July. In high availability averaged 2 litters; they 1.1 years, one three pregnant. size litters found live-traps 3.7. 1969, year excellent juveniles early bred during late summer. Subadults trapped June 40-70 days. Survival weaning following breeding season ranged 56%-58% (1967, 1970) 80% (1968); 17%-19% survived 3rd yr; 2%-3% 4th yr. overwintering success born lowest precipitation, poorest supply, reduced reproduction. Differential survival affected age distribu- tion season. One-year-olds dominated populations 1968 1970; but 1969 55% breeders preceding year. distribution little apparent effect population. parvus ceased aboveground activities summer autumn de- pending upon environmental conditions, sex, age. Population estimated by means Jolly-Seber stochastic model which helped interpret responses when components not trappable. peak autumnal varied mean 320 twofold variation estimates (206, 1968) (437, 1969) years. Within greatest fivefold increase numbers fall 1969. showed degree correlation amount precipitation falling October that largely stimulated growth reproduction vegetation, turn small-mammal 8 larger ranges (1,560-4,005 m2) than (508-2,301 m2); subadults. Home largest production moderate densities; smallest either resources densities or densities.