A Bear Out of its Lair

Meet wildlife biologist Dr. Lynn Rogers and some students at the den of a radio-collared black bear in winter. Dr. Rogers pioneered the technique of crawling into bear dens during their winter hibernation to tranquilize the sleeping bears. This allows him to gather data that has revealed much about seasonal changes in bear physiology. Dr. Rogers has also discovered new knowledge about bear families by radio-tracking black bears over several generations.

Click on photo images to enlarge for an up-close look at baby bears born in January!

Dr. Lynn Rogers has studied black bears in Minnesota's northwoods for most of his entire career.


To locate the den where a study bear was hibernating, Dr. Rogers carried an antenna that picked up signals from a radio collar worn by the bear. Mewing of the cubs could be heard from outside the den! The newborn cubs do not hibernate.


An assistant holds the needle that will be put on a pole, stuck far into the den, and used to inject the mother bear with a tranquilizer to keep her asleep while she is pulled out of her den and studied.


The two cubs were removed from the den first. Students had the important job of taking turns to keep the cub warm inside their clothing while it is away from its mother.


Mama bear sleeps on the snowy ground after being pulled from her den. A volunteer from the group crawled into the den to grab the mother bear. Then everyone formed a chain, grabbed his ankles, and TUGGED to pull both the volunteer and the bear out of the den.


The tranquilized mama bear yawns. Her fur is very thick. If you stuck your hand in it, the fur would bury your hand way past your wrist.


 Dr. Rogers will study blood samples and milk samples taken from the mother bear. She is also weighed. Her weight was 128 pounds. Most black bears lose between 15 and 30 percent of their body weight between early fall and late spring. Lactating mothers can lose as much as 40 percent of their body weight.


Baby bear will be suspended from this scale to be weighed. The cub weighed 3/4 pound (about as much as 3 sticks of butter) when it was born in January. It was blind and almost hairless. Now it is March, and the cub weighs almost 4 pounds.


Five long claws on each paw will help the bear grasp and dig into the bark of a tree as it climbs, and to dig and rake food to eat from the ground. But for now, this cub just feeds on its mother's milk. It will weigh about 7 pounds when the family leaves the den in spring.


Sleeping mama and her two cubs are stuffed back into their cozy den until it's time to come out in mid-April or May. They will hibernate with her next winter, too--but perhaps in a different den.When the cubs are one year old, they will be big enough to wear their own radio collars. Then Dr. Rogers will track and study them after they leave their mother and strike out on their own at the age of one-and-a-half years. 

Photos Wayne Kryduba


Try This! Journaling Questions/Activities
1. Check your library for BEARMAN by Laurence Pringle and Lynn Rogers. Before you read it, list questions you hope to find information about in the book.

2. How dangerous are black bears? Write your current opinion in your journal. Then visit the North American Bear Center. Go back to your journal and update what you wrote with new information from the site's slide show entitled How Dangerous are Black Bears?

3. Go to Journey North's Bear Facts page. Find at least three myths about black bears. Make a two-column chart and list the myth and, in the second column, a fact that shows the myth is false. Share your findings about black bears with family and friends.