Denning/Hibernation
Based on the Tensas and Atchafalaya River Basin studies in
Louisiana, the onset of denning occurs from late November to
early January. Activity, movement, and home range generally
decrease rapidly during this period as bears enter
“pre-dens” or nests, or enter the den where they will spend
the winter.Black bears are not true
hibernators. They go through a winter dormancy period termed
“carnivorean lethargy”, or torpor, which helps them survive
food shortages and severe winter weather. During the winter
“sleep” bears do not eat, drink, urinate, or defecate. Waste
products are recycled through unique metabolic and
physiological processes and there is no degenerative bone
loss during dormancy. Black bears exhibit varying degrees of
lethargy while denning, but most can easily be aroused if
disturbed.
Denning activity is influenced by a number
of factors: food availability, age, gender, reproductive
condition, photoperiod, and weather conditions. Generally,
pregnant females are the first to den and males the last.
Factors contributing to interruption of the denning period
or the changing of den sites during a given winter include
human activity, rapidly fluctuating water levels,
fluctuating extremes in weather conditions, and the lack of
concealment of ground dens. Data collected by monitoring
denning behavior indicate bears are more active in winter
months in the lower Mississippi River Valley than at more
northern latitudes. Recent observations indicate that some
females with cubs, especially in the coastal Louisiana
population, actively forage in the area near the den,
leaving their cubs for short periods and returning to care
for them.
For some bears, usually males, winter
inactivity may be nothing more than bedding for a few days
or weeks in one area before moving to new bedding sites.
Pregnant females, the first to seek den sites, usually
choose sites that are more secure and inaccessible than
those typically selected by males. Females prefer large,
hollow trees, as these provide dry, secure, and
well-insulated cover, but will also den in brushpiles and
thickets (see Habitat Requirements section). |
