During Wintertime in Northen regions, Icy, crusty-packed snow allows Fishers, Foxes and other carnivores to get out into the woods and achieve hunting success while conserving energy.....This, versus deep snow powder accumulations that make it near impossible for "hunters" to venture out in search of food

Predators Get Snowed In Too

By ROLAND KAYS

Roland Kays, curator of mammals at the New York State Museum and author of "Mammals of North America," writes from Albany, where he is comparing the behavior of fishers in urban and wild settings.

Snow changes everything out in the woods. Snow covers the ground, hiding vegetation from hungry deer, and mice from predators. As it piles up, it makes it difficult to even walk around. Animals have a rough time in the snow.

The purpose of our camera trapping survey is to compare the mammal communities at nearby wild and urban sites so we can compare food available to the two populations of fishers we are studying. Fishers are predators of medium and small prey; to understand how and why they have adapted to urban forests, we wanted to see what food is available to them. Judging from the fat squirrels I see at my home bird feeder and rabbits in my garden, I have a hunch (call it a hypothesis) that there is a lot of food in suburbia for a predator like the fisher.

To test this we are putting camera traps at random locations in urban and wild forests. Randomizing sampling is a standard scientific method, but has only recently been applied to camera traps. Historically, camera trappers have put out bait or placed their devices along game trails to get the most, or best, photos. These methods do get some great shots, and are fine for some scientific questions, but also introduce a number of biases to the data. What if some animals don't use game trails? What if animals in one area are hungrier, or bolder, and thus more attracted to your bait than others? What if some animals are afraid of the bait? To avoid these biases we use a computer to pick random points within our two study sites. We might get fewer pictures over all, but the data are more comparable between sites.

Checking camera traps is like a mix of fishing and Christmas. Finding pictures of common things like deer and squirrels is fun, like catching bluegills, but there's always a chance of catching the big one — for example, a coyote, fisher or other rare species. But instead of slowly accumulating catches over the day, you get them all on one memory card — let's pop that sucker in and see what we got!

Deer, yes, we've got a lot of deer in both the urban and wild sites. But over all I'm surprised at how few pictures we've gotten in these two weeks with snow, compared with earlier in the fall. It seems like all animals have decreased their activity with the snow. When we get back to the museum we'll enter these all into a database and crunch the numbers to do a statistical comparison between the urban and wild sites.

The thing that strikes me from the first look at these pictures is how many of the predators were photographed on the few nights when there was a nice icy crust to the snow. Of the three foxes and one fisher we photographed, all were during the three days with a crusty snow, with none on the 15 days with deeper snow. The video shows the foxes and fisher clearly walking around on top of the icy crust. They must have sharply increased their activity on those nights, taking advantage of the easy travel to hunt up some dinner, or traverse their territory for scent marking. We set these camera traps to compare urban and wild mammal communities but ended up with some surprise insight on the effect of snow cover on animals, and the joy of ice-skating foxes and fishers.