Denning ecology of two black bear populations in the Arkansas highlands

The denning ecology of one adult male and 29 adult females in the Arkansas Highlands was studied using radiotelemetry from fall 1988 through spring 1990. Research was conducted on the White Rock and Dry Creek study areas, in the Ozark and Ouachita National Forests. Denning chronology was defined; physical, vegetative, and site parameters were measured at each den. Canonical discriminant analysis was used to determine den habitat utilization and delineate important denning habitat components. Effects of roads on den selection were examined with the aid of a Geographic Information System and repeated measures analysis. Den and ambient temperatures were recorded in week~long intervals using circular thermographs. Den availability was estimated from searches made along random transects.

In 1989, pregnant females on both areas denned significantly earlier (p=0.0005) than females with yearlings and barren females. Barren females emerged from dens first, followed by females with yearlings, then females with newborn cubs. Significant differences (p=0.0001) in length of denning period were detected among all reproductive groups. During 1988 on Dry Creek, a year of high food availability, pregnant females denned later (p=0.0183) than in 1989, a year of low food availability. Differences in entrance dates between years were not observed among females with yearlings or barren females.

Bears on both areas utilized rock cavity dens (67.3%) most often. Excavation dens (18.4%), clearcuts (6.1%), tree cavities (4.1%), and open nests (4.1%) also were utilized. Rock dens occurred in creek bottoms (rock creek) and along bluffs (rock bluff). Rock creek and excavation dens were prone to flooding during winter dormancy. Bears that occupied dens prone to flooding were significantly younger (p=0.0444) than bears in dens secure from flooding. Roads did not affect den selection because road densities were low and traffic volumes were light during winter. Rock dens maintained a constant temperature that was cooler than day ambient temperatures but warmer than night ambient temperatures (p=0.0230).

A gradient of high structural security and inaccessibility existed from rock dens, to excavations, to dens in clearcuts. Security of excavation and clearcut dens was compensated by increased cover and higher understory stem densities. Differences in components of denning habitat did not exist between reproductive classes but were detected between study areas. Twenty-two potential dens were located on White Rock and none on Dry Creek. This discrepancy was related to the sampling technique and the scarcity of rock bluff dens on Dry Creek.

Rock dens are available on both areas and utilized at the highest rates. These dens provide the most structural security and persist for many years. Location of improved gravel roads may be related to rock den habitat on Dry Creek. Proximity of roads to rock outcroppings should be given consideration on both areas in future management plans.