A Bad Winter for Rodents

Great Gray Owl

Adult Great Gray Owl © Brian E. Small/VIREO

It’s been a very mild and almost snow-free winter in Manitoba so far this year. Good news for us. Bad news for mice and shrews and voles. They rely on a thick blanket of snow to survive the winter.

A couple of years ago as I watched a Great Grey Owl along a road in the boreal forest east of Winnipeg, it suddenly left its perch on a hydro pole, swooped over the road-edge, and plunged, talons-first, into the thick snow. It immediately extricated itself and flew back with a small, squirming rodent.

Wow! I wondered. How’d it do that? I knew that owls had great hearing. But the snow was at least a foot thick. That, it seemed to me, was like me hearing a pin drop a block from my house.

Meadow Vole © Rob & Ann Simpson

And what was a rodent doing in a snow-bank? I thought they hibernated all winter or found a warm place like my basement to hang out.

That’s when I first heard about pukak.

Pukak is that small space under the snow and above the ground that forms when the snow piles up more than a foot or so and when the earth’s warmth melts the bottom layer to form passageways for insects, rodents and tiny mammals.

Cinereous Shrew © Audubon Guides

Mice and shrews and voles use these passageways to seek out seeds and grasses and bugs left over from the summer and fall. At irregular intervals vents form to allow gasses to escape. Owls listen to the tiny noises that emanate from these vents.

House Mouse © Rita Summers

With barely three inches of snow on the ground this year, pukak hasn’t yet formed. That means the rodents can’t leave their winter hideouts. They don’t have to worry about owl attacks, but they are in danger of starving. The thicker the snow, the better their chances of surviving the cold.

Gene Walz

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2 Responses to “A Bad Winter for Rodents”

  1. Michelle says:

    I wondered about this as we haven’t had much snow here in western NY and I have seen the vole trails in past years…

  2. Tyler says:

    Such a strange year in regards to weather. Not a very cold winter and it looks like summer is going to be pretty mild.