Emigration and Survival of 2-Year-Old Male Elk in Northwestern Colorado
Citation
A William Alldredge, and Mylea L Petersburg, Emigration and Survival of 2-Year-Old Male Elk in Northwestern Colorado: .
Summary
Wildlife managers in northwestern Colorado have had difficulty accurately estimating numbers of subadult male elk (Cervus elaphus) by sampling winter population densities and sex ratios. We investigated emigration and survival of telemetered 2-year-old male elk in a trophy hunting area in a northwestern Colorado Game Management Unit (GMU) to evaluate management strategies. We hypothesized that skewed numbers of males resulted from high subadult mortality or dispersal of subadult males. We used telemetered elk and Kaplan-Meier staggered entry methods to estimate emigration probability of 0.56 and 0.33 in 1995 and 1996, respectively. Maximum distances moved by emigrants from their capture point averaged 87 km (median = 79±6.8 [SE]) [...]
Summary
Wildlife managers in northwestern Colorado have had difficulty accurately estimating numbers of subadult male elk (Cervus elaphus) by sampling winter population densities and sex ratios. We investigated emigration and survival of telemetered 2-year-old male elk in a trophy hunting area in a northwestern Colorado Game Management Unit (GMU) to evaluate management strategies. We hypothesized that skewed numbers of males resulted from high subadult mortality or dispersal of subadult males. We used telemetered elk and Kaplan-Meier staggered entry methods to estimate emigration probability of 0.56 and 0.33 in 1995 and 1996, respectively. Maximum distances moved by emigrants from their capture point averaged 87 km (median = 79±6.8 [SE]) in 1995 and 149 km (median = 136±24.7) in 1996. Survival of emigrants was 0.25±0.07 for both years combined. Resident survival was greater in both years at 0.89±0.05. Our results suggest that elk movement between management areas in northwest Colorado is prevalent. Losses of males from the 2-year-old age cohort were attributed to high emigrant mortality and dispersal. Monitored elk dispersed throughout west-central Colorado and into parts of Utah and Wyoming. In addition, many harvested 2-year-old males had antlers that would have resulted in misclassification into older age categories by biologists during winter population surveys. We recommend conducting small-scale studies to identify local population dynamics, coordinate hunting seasons and population surveys, and align management boundaries with biological groups of elk.
Published in Wildlife Society Bulletin, volume 28, issue 3, on pages 708 - 716, in 2000.
