Randy Cross and Jen Vashon along with contractors, Lisa Bates and Matt O’Neal and volunteer, John Wood of the Maine fish and wildlife department recently finished our winter bear den field season.
Among the highlights, we successfully deployed a live-stream web camera in an 8 yr old bear’s den on Jan 11th after beginning den visits on a regular basis on Jan 6. This bear gave birth to 2 cubs on Jan 16th. The den cam installation was part of a cooperative effort with a privately funded nonprofit group that is hoping to raise funds to help wildlife research in Maine (Wildlife Research Foundation).
We finished the winter field season on March 28 when we visited two 15 yr old females for the second time this winter in northern Maine. These bears were first weighed while pregnant on Dec 29th and Jan 3rd. They lost 60 and 65 lbs in 85 and 90 days, respectively, since we handled them earlier in the winter (ID 1592 had 3 cubs – total combined wt of all 3 cubs = 13.1 lbs, and ID 1574 had 2 cubs – total combined wt = 14. 6 lbs) ; Both of these bears traveled about 2 miles from their first den to their second den.
We visited 75 dens this winter, handling a total of 165 bears. We handled 38 yearling bears (19Females, 19Males) in 20 dens and 60 cubs in 26 litters (30Females, 30Males; 2.31 cubs/litter). There were 2 litters of 4 in Bradford study area, and only 3 single cub litters (2 in Bradford study area, and 1at Spectacle Pond study area). Last year’s cub survival was 79.7% (47 out of 59 cubs that were handled last year were seen in the dens this year as yearlings). This rate of survival to one year of age is higher than our long term average which is closer to 70%.
One important piece of information that we are able to gather every winter is the weights of bears that are just over one year old (yearlings) who are in the den with their mothers. These yearling weights are our most sensitive indication of the relative abundance and quality of food resources available to all the bears during the preceding summer feeding season. This winter, yearling weights averaged 53.0 lbs for all yearlings combined which is a relatively high average indicating that last spring, summer and fall was a particularly good natural food year for bears in Maine. This was especially true for bears living in the big woods of northern Maine where yearling bears averaged a whopping 61.8 lbs. For comparison, In leaner times, yearling weights tend to average closer to 30 lbs like the 9 year period from 96-04 when they averaged just under 27lbs in our northern study area.
Every den season holds its own surprises. This winter we had 6 bears denned in hollow trees above the ground (5 were nested greater than 25 ft above the ground). We have seen less than 12 bears denned this high in trees in the previous 29 years combined (close to 1500 dens). We successfully handled 5 out of these 6 thanks to Bill Hanson, a professional tree climber from FPL who spent 3 days helping us.