Population Dynamics of the Western Jumping Mouse (Zapus Princeps) During a Four-Year Study

A live-trapping study of the western jumping mouse ( Zapus princeps ) was conducted in a willow-sedge bog adjacent to a montane stream in the Laramie Mountain Range of southeastern Wyoming from August 1965 through June 1969. Population densities were quite stable during the 4 years and varied from a high of 1.8 mice per acre in August 1967 to a low of 0.9 mouse per acre in June 1966. Insufficient energy stores appeared to be a major source of juvenile mortality during the long period of winter hibernation, with an average of 55.6 per cent of young not being taken in traps the following spring. the over-winter loss of adults was much lower, averaging only 16.5 per cent. Summer disappearance rates for adults and young adults were nearly identical, averaging 27.3 and 30.0 per cent, respectively. Some jumping mice exhibited remarkable longevity for small rodents, surviving as long as 4 years. the estimated mean life span of 28 jumping mice was 16.5 months. the average home range length of 32 adults was 572 feet, with males averaging 691 feet and females 510 feet. Home ranges of most jumping mice tended to be extremely elongate and to parallel a stream that crossed the study area. the seasonal, cyclic weight changes of the species were of considerable magnitude. At least 10 other species of small mammals were associated with Zapus on the study plot.