Age Determination of Live-Captured Beavers by Weight in Southwest Montana (Poster)


  • Ashley E. Micklewright Department of Ecology, Montana State University, Bozeman
  • Torrey Ritter Department of Animal & Range Sciences, Montana State University, Bozeman
  • Lance McNew Department of Animal & Range Sciences, Montana State University, Bozeman


Studies evaluating demography and age specific space use of beavers (Castor canadensis) require accurate methods for aging live captured individuals in the field. Unfortunately, techniques for aging live captured beavers in the field are often unreliable and can require previous experience in handling beavers. Previous age weight relationships developed in other regions (e.g., Midwest) may not be suitable, because differences in diets, seasonal behavior, and selection for life history traits likely results in significant regional variation in age weight relationships. Thus, regional assessments of age -weight relationships are necessary for accurate inference. In the fall of 2015, we began a two -year study with the goal of developing accurate growth curves for beavers occurring in southwestern Montana. We are collecting beaver carcasses from local trappers and animal control experts. Carcasses are weighed and the molar teeth extracted for laboratory analysis of cementum annuli which provide an accurate age for each beaver. Regression analysis will be used to model age weight relationships for beavers, and model predictions will be tested using a hold out dataset and cross validation. We expect our results to provide useful information for researchers in forested headwater habitats of Montana, and provide baseline data for calibrations for broader scale assessments in the region. Please contact us if you can provide whole beaver carcasses.






Biological Sciences -Terrestrial Ecosystems [Poster Abstracts]