Weights and morphometrics of black bears in the southeastern United States

Weights and body size measurements (morphometrics) of mammals may vary throughout the range of a species for different reasons. Populations may vary genetically, demographically, or nutritionally, any 1 of which (or combination thereof) could alter the weights and morphometrics of its constituents. The objectives of my study were to determine if black bear (Ursus americanus) populations vary in weights and morphometrics and, if so, to determine if these differences correspond to current subspecies demarcations or, alternatively, to regional habitat quality indices. I also determined the level of variation introduced into morphometric data when multiple researchers collect field data. I compared the summer weights and morphometrics of 260 adult black bears, collected from 20 locations throughout the Southeast and selected other areas in the United States from 1992 to 1994. I estimated missing data points using multiple regression analyses and combined the sexes using sexual dimorphism correction factors. I partitioned the 20 populations based on 1) traditional subspecies demarcations of black bears and 2) Bailey's (1980) ecoregion province delineations. Then, I determined the optimal clusterings of these partition schemes using the minimum of Akaike's information criterion (AIC) and information complexity based on the inverse-Fisher information matrix (ICOMPIFIM) in multi-sample cluster analyses. Black bears in both the subspecies and ecoregion province partition schemes grouped separately based on their weights and morphometrics in the multi-sample cluster analyses. Therefore, there was evidence supporting the subspecies demarcations, but there was also evidence that this classification may not account for all of the morphometric variation found in black bears in the eastern United States. I concluded that U. a. americanus, U. a. luteolus and U. a. floridanus were morphometrically distinct subspecies, but that there may be additional morphometric differences within the range of U. a. americanus The weight and morphometric differences indicated by the multi-sample cluster analyses, however, were not correlated with regional habitat quality indices as measured by: crop yields, latitude, actual evapotranspiration, and soil fertility. Additionally, in Great Smoky Mountains National Park (TN) and Neuse-Pamlico Peninsula (NC), black bears exhibited inter-year differences in weights and morphometrics. Therefore, I hypothesized that black bears may respond temporally to habitat quality at a sub-regional level. I estimated the variation in morphometrics of black bears (Ursus americanus) taken by 6 field researchers. Eight body measurements were recorded by 3 teams of 2 researchers on a total of 70 black bears in Great Smoky Mountains National Park in Tennessee and North Carolina. Measurements were summarized to determine the intra- and inter-researcher variation present in the morphometrics. I then ran simulations on predictive equations to determine how the observed variation affected the results. The intra-researcher simulations differed from one another by 1.5 - 2 .6% of the average of the predicted parameters and the inter-researcher simulations differed from one another by 3.4 - 8.1% of the average of the predicted parameters. These differences may explain some of the error associated with analyses and predictive equations based on morphometrics. Consequently, it is imperative for researchers to minimize the error of taking measurements by developing stringent standards for data collection and by reducing the number of personnel involved in data collection.