Spatial Variation in Sexual Size Dimorphism of the American Black Bear (Ursus americanus) in Eastern North America
Abstract
Spatial patterns of sexual size dimorphism for the American black bear (Ursus americanus) from 12 localities in eastern United States were investigated. Forty-four measurements from 371 (187 males and 184 females) adult specimens (≥4.5 years old) were recorded using digital calipers. Males were larger than females for all characters except braincase width and length of M3 for specimens from Virginia. The degree of sexual size dimorphism (SSD) for characters across localities ranged from 4.1-22.5%, with most being from 6.6-17.0%. For 39 of the 44 characters (88.8%), there was no statistically significant difference in degree of SSD across localities, indicating it was approximately the same at each locality. This was further supported by results of principal component analysis. Results followed a similar pattern reported for U. americanus in western North America, which supports a growing generalization for medium-sized and large-sized terrestrial carnivores of a uniform pattern of sexual size variation across geographic space; this is likely due to bioenergetic factors associated with growth and reproduction, with selective pressure responsible for size dimorphism acting uniformly throughout the range of the species.
Publication Title
Southwestern Naturalist
Recommended Citation
Pope, B., Kennedy, P., Mech, S., & Kennedy, M. (2017). Spatial Variation in Sexual Size Dimorphism of the American Black Bear (Ursus americanus) in Eastern North America. Southwestern Naturalist, 62 (2), 143-150. https://doi.org/10.1894/0038-4909-62.2.143
