Reproductive Biology of Black Bears in the Smoky Mountains of Tennessee

Information related to the reproductive biology of female black bears (Ursus americanus) was collected in the Smoky Mountains of Tennessee. Denning and weight information were also collected.

The majority of females utilized tree dens. The denning period averaged 114 days, with most females entering dens during the first 3 weeks of December and emerging from dens between the first and last week of April. Females with newborn cubs denned longer and emerged from dens later than females without offspring. The date of den emergence for females for females was used to effectively predict reproductive condition (with newborn cubs or without offspring).

Average litter size, determined from den work during 1979-80, was 2.5 cubs, with average litter sizes of 2.2 and 2.7 during 1979 and 1980, respectively. Tape recording in tree dens was an effective method for determining the presence of cubs and estimating litter size.

Most breeding activity was observed during the last week of June and the first 3 weeks of July. The majority of sub-adult females that exhibited signs of estrus were without offspring the following winter. Vaginal smears were useful in verifying estrus in female black bears.

Minimum reproductive age was 4 to 5 years, with most females giving birth for the first time at age 5. The majority of females exhibited a regular pattern of consecutive reproductive cycles: breeding and giving birth during alternate years. However, a substantial number of females skipped a year between reproductive cycles at some time during their life, probably due to mast availability and the nutritional condition of the female.

Only 1 female was observed lactating during successive years, indicating that losses of whole litters is uncommon. Average litter sizes determined from den work for females with newborn cubs and yearlings were 2.5 and 2.0, respectively, indicating that some cub mortality does occur.

Wild female black bears reached mature weights from 4 to 5 years of age. Panhandler females reached mature weights earlier and weighed more than wild females.