Abstract We describe population estimates, survival rates, and aspects of hibernation for a population of Zapus hudsonius preblei along a 3.7-km section of South Boulder Creek and 2 associated outflow ditches in Boulder County, Colorado. Mark-recapture analysis was used on 352 marked jumping mice with 722 captures from 6 paired sites along the creek and 2 sites on ditches. Linear population density estimates ranged from 22.7 ± 7.9 to 79.5 ± 33.3 animals/km of stream-reach for the 6 sites combined along South Boulder Creek, and from 33.9 ± 1.6 to 85.6 ± 30.3 animals/km along the occupied ditches. This study highlights the potential importance of irrigation ditches as suitable habitat for Z. h. preblei. Estimated over-winter survival rate for both sexes combined was 54.1 ± 18.8%, summer survival rate was 16.2 ± 9.6%, and combined annual survival rate was 8.8 ± 6.0%. We suggest that good hibernation habitat is important for these populations to offset low summer survival. First emergence from hibernation was...