When Will the Bears Den? - UPDATE August 16, 2021
Mystery Mom w/2 cubs
Mystery mom w/2 cubs
A question today was:
"We have been having a discussion wondering if the really hungry bears will den earlier so they are not expending calories looking for non-existent food or if they will wait longer to den so they can try to find more food and hopefully put on more weight. Hoping you can shed light on that."
With myself waiting to see what the bears will do in this second year of drought and scarce berries, I gave some general information on it, saying:
As the research continues, questions get harder to answer. It was easy in the beginning with sample sizes of one. Now, bell-shaped curves make it harder—some will do it one way and some another. Plus, data varies across the continent. Bears in the different regions have evolved to fit the regional norms of plant growth and fruiting, but late frosts and summer droughts make big differences in berry crops—especially in our study area where the Laurentian Divide that has shallow, sandy soil over bedrock lets water evaporate more readily during droughts. But, in general, bears around here den about the same time each year whether food is abundant or not, and that includes supplemental food. Providing bears with food around here has long failed to keep them up longer into fall. Thousands of years with no fall food has created a fairly strict internal schedule.
On the other hand, in the eastern deciduous forest with thousands of years of variable fall crops of acorns, beechnuts, hickory nuts, and other foods have led to great variability in the hibernation schedule. For example, some bears there remain active all winter if a good beechnut crop is available under the snow. People that provide supplemental food there see bears all winter.
Local exceptions here in the Ely area are described in publication number 55 under published papers on bearstudy.org: Rogers, L. L. 1987. Effects of food supply and kinship on social behavior, movements, and population dynamics of black bears in northeastern Minnesota. Wildlife Monograph No. 97, in the section "Prehibernation Activities" (pages 37-38). There is also related information in the section "Foraging Period" "Late Summer and Fall Travels" (pages 31-34).
I'm looking forward to seeing what we will learn here this fall if hunters don't kill too many of the study bears in September.
On another subject. Lucy was accompanied by both her cubs today, including independent Desi. It was also nice to see the mystery mom with her two cubs, but the picture still doesn’t include her faint chest blaze that is shaped like a W that we want to have on record. Still trying.
Thank you for all you do.
Lynn Rogers, Biologist, Wildlife Research Institute and North American Bear Center
