Fed bear survival and water in the den
Fed bear survival and water in the den
Update March 10, 2010
We do our best to respond to the questions thrown at us, but we don’t get to them all. Sometimes we just don’t know the answer and other times the number-crunching to give precise answers would take too much time away from research.
One number-crunching question we thought we’d try is, “What is the survival rate of fed bears versus other bears.”
Comparing fed bears with other bears threw us because virtually all the bears here are fed by people—either by residents or hunters. In the study area, bears are perhaps fed more than in other areas. A dozen or so residents have been feeding the bears here for over four decades, but the small amount of food they provide is dwarfed by the tons of food hunters put out as bait each year from mid-August to mid-October.
So, we assumed the question referred to bears fed by residents and that is virtually all the bears in the study area. Some more, some less. Some disappear for years and then check back. No bears depend on the supplemental food. But the supplemental food, also called diversionary food, does keep them out of trouble and keeps them from getting shot by landowners in years when natural food is very scarce. They go to feeding stations where they are welcome rather than to places where they would be shot. As a result, nuisance problems are lower in the study area than elsewhere.
We’ve said that the research bears survive at a higher rate than other bears in the state. Someone suggested that this is because hunters spare radio-collared bears because of the ribbons on the collars. We like to think that’s true. The average age of the 8 bears (all female) wearing collars at this moment is 6.6 years (range 2-11 years). Compare that to the average age at which bears are killed by hunters, which is 2 years for males and 3 years for females. That’s a little like comparing apples and oranges because it compares the average age of radio-collared bears with the average age at which bears are killed in the overall population. We would rather compare the average age of the radio-collared bears with the average age in the overall population, but nobody knows that—not the DNR, not us. The closest we can come to that is from a study we did back in 1971-1975 when the average was found to be 5.4 years, excluding dependent young. But that number is from 35 years ago.
However, there’s more to it. Back to today. Although the average age of the 8 radio-collared bears is 6.6 years, the average age of 19 non-radio-collared bears (10 males, 9 females) we’re watching is 9.8 years (range 4-26 years), again excluding dependent young. All of these are fed by people. The fact that these non-radio-collared bears average older calls into question the explanation that the higher survival of research bears is entirely due to hunters sparing the radio-collared ones. We can offer other explanations, but this update is already getting long and is so crowded with numbers that it’s not good reading.
In conclusion, although the average age at which bears are shot in the overall population is 2 for males and 3 for females, the average age of the 27 research bears we are watching (radio-collared plus non-radio-collared) is 8.6 years (range 2-26), excluding dependent young. There are many ways a person could calculate this, all with incomplete data, but we feel safe in saying the research bears, all of which are fed by residents, survive at a higher rate than bears in the overall population, and we don’t entirely know why.
As we’ve said before, there are many misconceptions about what happens if bears are fed. Most people know that food can lead bears into trouble, but there is very strong evidence that food can also lead bears out of trouble. We are continuing to explore that.
The most important bears in the research are the radio-collared ones. We are seeking cooperation from hunters in sparing those, which should further contribute to their higher survival rate compared with non-research bears.
The loyal den-cam watchers have had front row seats for the excitement of the last couple days. Lily ventured out of the den briefly yesterday and gave us another good look at Hope alone in the den. We could see some moisture seeping into the den, but the main portion of the den appeared dry. Many noticed Lily’s fur was damp when she re-entered the den—likely from the tight squeeze against the wet den opening as she went out and back into the den. There is so little snow around the den—and the ground slopes away from the den—that Lily likely won’t have much trouble with water in the den.
Lily nearly exited her den twice today. She may have been trying to gather more bedding—something commonly done by bears in response to moisture in the den. Each time she quickly backed back into the den in response to Hope’s cries.
For more information on how mother bears deal with water in the den see 'Dealing with Water in the Den'.
Thank you again for your continued support of this project and our ongoing educational efforts.
—Lynn Rogers and Sue Mansfield, Biologists, North American Bear Center