American black bear estrus and parturition in the Alleghany Mountains of Virginia

Abstract

Timing of parturition and, to a lesser extent, estrus, are rarely explored aspects of American black bear (Ursus americanus) reproductive ecology. The Cooperative Alleghany Bear Study was an intensive 10-year multi-faceted research project conducted on 2 study areas in western Virginia. We examined timing of estrus based on 430 observations of 326 lone (without cubs at the time of capture) female bears from late May–August, 1994–2002. We estimated parturition date for 383 cubs from 150 litters born from 1996–2003 to 99 individual females ranging from 3–24 years old. Bears were documented in estrus from late May through August with a peak during early July. Parturition dates ranged from late December to mid February with most births occurring in mid January. Three- and 4-year olds gave birth, on average, 12 days later than older bears. We suggest parturition date likely affects den exit date and perhaps cub survival, an area requiring further inquiry.