Estimating the Live Body Weight of American Black Bears in Florida

Measuring the live body weight of large-bodied animals can be impractical when equipment needed to weigh individuals is inadequate or unavailable. My objective here was to develop a model to accurately estimate the live body weight of black bears Ursus americanus floridanus in Florida based on the relationship between scale weight and sex, morphometric measurements, and age predictor variables obtainable in the field. I used an information-theoretic approach to evaluate simple and multiple linear regression models with 70% of the data, and evaluated the best model in the set using the remaining 30%. A sex-specific model was sustained because the intercept and coefficient of age variable in female and male modeled relationships differed significantly. Chest girth 2 was the best single predictor of body weight in each sex. A model including age, age 2, and body length variables was better supported than chest girth 2 alone. I also created a reduced model to estimate body weight when personnel may not have an opportunity to determine a bear's age. Even though there was decreasing support for the reduced model, differences between the observed and estimated body weight of all models applied to the validation data set were not significant. The 95% confidence interval on the bias of the best model ranged from -1.9 to 1.6 kg in females and -1.4 to 2.1 kg in males. The 95% confidence interval of the reduced model ranged from -1.8 to 2.3 kg in females and -2.5 to 0.5 kg in males. The body weight estimation models can be used to provide more live body weight data from handled black bears in Florida that are not weighed with a scale.