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Where Did They All Go ?...Black Bear Winter Denning
                                                                                             By DHenry


After regularly seeing bears throughout most of the year, black bears in our area are missing from the landscape during the winter months. Black bears have entered their winter dens to avoid the rigors of winter and will spend several months hidden in seclusion and for some, giving birth to a new generation of cubs. Generally black bears are considered to be hibernators, implying that they spend the winter in a dormant or lethargic state. Although some will correctly point out that they are not "true hibernators" because their body temperatures only decrease a few degrees and they do not become fully comatose like woodchucks, bats and some small rodents. Nonetheless, black bears become semi-dormant during which time they do not defecate, urinate, eat or drink and can lose up to 40% of their body weight. The adult females (sows) also carry out the gestation and give birth to their cubs in the dead of winter. Sows will usually breed every other year and the cubs born in the previous year will enter the den with, and spend a second winter with their mother before establishing a territory of their own.


 

NYSDEC did extensive research on black bear denning behavior in the Catskill region in the 1970's. The Catskill Mountains have an abundance of rock formations which offer suitable den sites. Bears will also den in hollow trees, brush piles and in some cases in a simple depression in the ground. Interestingly, they have also been known to den in some pretty strange places including under porches of occupied homes and in some instances road culverts.

During the research, bears that were equipped with radio collars were monitored to determine their actual denning dates. Sixty-two (62) den entries were confirmed. Females with young of the year cubs entered their dens on an average date of November 22. Females without cubs had an average denning date of November 24 and adult males had an average denning date of December 10. Availability of natural foods can impact this schedule. When natural food is scarce (like the fall of 2012), bears entered their dens earlier and hunter harvest is reduced. Conversely, when natural food was abundant, they tended to stay out longer and in those years bears were subject to heavier hunting mortality.


Black bears will often line their den floor with leaves, branches and evergreens. While in the den, adult bears survive by utilizing energy from their fat reserves. After they have finished feeding in the fall, their digestive sytem shuts down, and bears form a fecal plug from leaves, twigs, hair and pine needles that can be up to 12 inches in length. Any urea they produce is resorbed in their bodies, and adult bears neither defecate nor urinate while denned. Interestingly, bears typically shed the skin on their foot pads near the end of the denning period. Front foot pads are usually shed in a single piece, while rear pads are often lost in several pieces. During the entire time that they are denned, they are capable of being aroused by human disturbance and if disturbed may often vacate the den for a brief period of time.

Similar research was done in the Catskills regarding the timing of bears emerging from their dens in the late spring. A total of 38 den exits were documented. Leaving the den occurs in the reverse order that bears enter their dens in the fall. Males typically leave the den on an avererage date of about March 26, while females with last year’s cubs (that are now yearlings) exit about April 5. Barren, unbred females left the den around April 8, while sows with newborn, young of the year cubs did not fully do not fully leave  their den until around April 15.


Since most of their diet is vegetation, food is often scarce for newly emerging bears in the early spring. Succulent spring plants such as skunk cabbage and red maple buds are preferred early food for hungry bears. Newly born cubs typically have reached a weight of about five pounds by the time they leave the den with their mother. Cubs avoid predation and other dangers by climbing a tree when the sow gives a distinct vocalization, and will remain treed until such time as she signals another "all clear" vocalization.


By late June yearling bears disperse from their mother. The sows will come into estrus in late June, starting the two year circle of life in the world of black bears.


Interestingly the oldest black bear recorded from the Catskill Region during the 1970's bear research was a 41 year old sow. One can only imagine how many cubs she produced during her long lifetime.

 

 

 





















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