Warm weather and hibernation

Warm weather and hibernation

March 9, 2010 7:15 PM CST

Lily's den - March 9, 2010What will Lily do in this warm weather?  Temperatures this past week have been like mid-April (40-55F) when bears around here usually emerge.  Lily did come out briefly this afternoon, which prompted me to go to the den to check her tracks to see what she did.  I found no feces, so I suspect she came out only to eat snow, which she has been doing a lot lately.  The snow is melted away from the den, so now she has to exit to get snow.

The fact that I couldn’t find any feces makes me think I was wrong to guess she defecated when she came out just before giving birth.  Donna exited and defecated about that time, but Lily must not have had to go yet.

The den entrance looked extra dark colored like it was wet from the melting snow.  Lily’s fur was damp, too.  Not to worry about Hope, though.  Lily’s job is to lick every drop of moisture off of her.  If it gets too wet on the den floor, Lily can find a place in Lily’s fur that it reasonably dry.  The 3-day forecast includes rain, so water could be an issue in this unseasonably warm spell.

With Lily being fairly active today, I thought she might come out and let me get a heart rate.  But no, the cub decided to nurse.  When the cub makes the nursing hum, Lily holds still.  I waited until they were done but then found Hope snuggled such that Lily couldn’t move without disturbing her.  So it was a no go for seeing the cub, getting a good picture to post, getting Lily’s heart rate, etc.

I called Sue from the top of the hill to see when Sue noticed Lily perking up to listen for me.  I was still about 150 feet from the den, and Sue said the microphone was picking up my sounds loud and clear.  Lily certainly could hear me then, but Sue said she didn’t stir hearing my familiar voice.  The sensitive microphone magnifies sounds from inside the den and sounds that are far away.

People in Ely ask me if bears will be coming out in this warm weather.  Maybe briefly like Lily did today, but not to roam.  There’s no bear food in the northwoods now.  It’s not like New England and across the eastern deciduous forest where a good beechnut crop can keep bears pawing down through the snow all winter.  Here in the northwoods there is little oak, no beech, no hickory, and no other nuts to seek in winter.  The only nut around here is the hazelnut (filbert), and squirrels eat those up.  Any bear that got fooled by warm weather here would waste fat and energy and be at a disadvantage compared to other bears when it came to recovering and gaining enough weight to maintain the next pregnancy, so that trait would soon be bred out of the local strain, which it apparently has been.

Black bears in different regions behave differently in winter.  In the northwoods, most stay in all winter.  By winter, we mean mid-October through March.  Pregnant females and the biggest males often enter dens in early September.  Mothers with cubs are among the latest to enter dens.  Yearlings are also late.  Late around here is late October or occasionally early November.  Contrast that with areas where acorns and nuts are available.  Late November and December are typical dates there.  Bears in northern Minnesota abandon abundant food to hibernate on time.

Not so farther south.  Where people feed bears in North Carolina and Maryland, many bears stay up all winter.  In Florida, most naturally stay intermittently active except mothers giving birth.  They must stay with the cubs and care for them like Lily is doing.

Most black bears emerge in late March or April, but some stay in dens until early May farther north—especially if they have newborn cubs.  The way Lily’s single cub is growing, I suspect she will be ready to follow mom by early April.

Thank you again for your continuing support.

—Lynn Rogers, Biologist, North American Bear Center

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