Criteria to Improve Age Classification of Antlerless Elk

Wildlife managers routinely survey age and gender compositions of elk (Cervus elaphus) during winter to assess population demographics and to prescribe and evaluate harvest strategies. We measured precision of replicated field classifications of antlerless elk conducted during 1996-1999 on the National Elk Refuge, Wyoming. We found classification discrepancies of 14% for elk calves. Next we examined morphometrics collected from 349 individuals from 2 populations of elk in northwest Wyoming. A model constructed from the combined data set accurately predicted the ages of 93% of calves, yearlings, and adults. There were age-specific, quantitative differences in head morphology among calf, yearling, and adult elk. Using quantitative differences and photographic images, we developed illustrations and descriptions that can help observers distinguish calves from older elk. Use of these guides should improve indexing of population recruitment, based on calf:cow ratios, that wildlife mangers use to model population growth and to design annual harvests.