Black Bears

Black Bears are a common sight in many national parks.

NPS / Neal Herbert

Black Bear

Article by Hannah Lepper, Auburn University

Background

Black bears (Ursus americanus) are historically native throughout the entire state of Alabama (Cowan 1970, Edwards 2002, Scheick and McCown 2014). However, due to over-harvest and habitat degradation, black bears were nearly extirpated from the state. For several generations, the only black bears that remained in Alabama were around the Mobile River Basin. Recently, however, black bears from the north Georgia population have begun naturally recolonizing northern Alabama (Draper et al. 2017). Today, black bears can be found throughout Little River Canyon National Preserve.

Diet

Black bears are opportunistic omnivores, meaning that they eat almost any type of food. Some common foods are berries, grasses, insects, nuts, acorns, corn, and sometimes small mammals (Rogers 1976, McDonald and Fuller 2005, Elowe and Dodge 2007, Tri et al. 2016). Unfortunately, bears have also learned that bird feeders, deer feeders, trash cans, and other human-provided sources can be easily accessible. It is important to avoid providing human foods to black bears so that they do not become a nuisance. In the fall, bears enter a period called “hyperphagia.” During hyperphagia, bears can spend up to 20 hours a day feeding in order to prepare for winter hibernation.

Behavior

Hibernation is when bears spend winter months in a state of dormancy, usually inside of a den such as a rock crevice, tree cavity, brush pile, or rootball from a blowdown. During hibernation, bears have a decreased heart rate, lower temperature, and take fewer breaths; they do not eat, drink, urinate, or defecate (Nelson 1988, Oli et al. 1997, Hellgren 1998, Donahue et al. 2006). Additionally, mother bears give birth to cubs in the den; usually one to three cubs, every two years.

Female bears (called sows) are bred by male bears (called boars) between about May and July. Once a female has been bred, she goes through a process called “delayed implantation,” in which the fertilized embryo stops developing (Rogers 1976). Later on, around November, the embryo implants and starts development (Rogers 1976). The mother will give birth to cubs in the den in January or February. The cubs will stay with their mother for about a year and a half. When the cubs are a year old, they den together with their mother. The following spring, the mother will encourage the cubs to disperse so that she can come into estrous and be bred again.

The average female home range is about six to ten square miles, while males can roam more than 25 square miles (Edwards 2002, Lee and Vaughan 2003, Scheick and McCown 2014, Draper et al. 2017). Adult females generally weigh 125-175 pounds; adult males generally weigh 250 pounds or more (Rogers 1976, 1987).

Conservation Efforts

Auburn University and the Alabama Department of Conservation and Natural Resources are currently researching black bears in Alabama. One of the research goals is to investigate differences in cub survival between the two populations- the Mobile River Basin population and the northern Alabama population. Anecdotal evidence suggests that cubs in the Mobile River Basin population are not surviving, which means they are not being recruited into the population, and the population isn’t growing (Draper et al. 2017). Conversely, cubs in the northern Alabama population do appear to be surviving and recruiting into the population. Potentially, these differences in cub survival may be driven by differences in den habitat and structure. Dens in the northern Alabama population, especially around Little River Canyon, provide structure in the form of rock crevices, tree cavities, or brush piles. These structures offer protection to the newborn cubs from weather and predation. Conversely, the general paucity of structural dens in the Mobile River Basin population means that bears are denning in a leaf bowl or ground nest. These types of dens leave newborn cubs vulnerable to weather and predation, and may be negatively affecting cub survival.

In addition to cub survival, one of the research goals is to look at how and where the current populations could expand. Namely, male cubs that survive to dispersal age (1.5 – 2.5 years old) could venture far from their mother’s home range. Juvenile dispersal and population expansion are understood by utilizing black bear GPS collar locations. Location data obtained from GPS-collared black bears can provide insight into where black bears are traveling and potentially predict where current populations may expand to in future generations.

Understanding black bear population dynamics is essential because black bears are “umbrella species,” which means that conservation and management efforts that support black bears additionally support many other species as well- both plants and animals. Because bears cover such a large area, conservation of black bear habitat is crucial for population persistence. Lastly, black bears are Alabama’s state mammal, so it is important to conserve and manage the species for future generations to enjoy.