The Wild Side: The importance of winter
This winter is being uncooperative. I don’t think I have unreasonable expectations for winter; we should have below freezing temperatures, and we should have periodic snowfall. We shouldn’t need to postpone sled dog races or close snowmobile trails. But here we are in January with areas of bare ground and lakes with less than a foot of ice. Winter is important. It resets our lives, our way of thinking. When I lived further south, I found my year wasn’t the same without snow. Just seeing leafless trees and dead grass for a couple of months doesn’t count. Winter gives us a new starting point for the year, where spring can follow with new life and a sense of place.
The winter does some important wildlife management work as well. It sets back disease and parasites. It manages wildlife populations, reducing numbers of sick, weak and lame animals while protecting others. For example, in a mild winter, 10 percent of our deer herd dies. In a severe winter, 20 percent or more of our deer die. But other wildlife need snow cover to survive. Ruffed grouse plunge themselves into snowdrifts to stay warm while avoiding predators like hawks and foxes. These birds need some roosting snow for maximum overwinter survival.
American marten, Wisconsin’s only endangered mammal, move about on snow easier than fisher, one of their major predators. Deeper snow might help them avoid predators as well. When we get periodic snowfall, and the snow sticks, many of our Northwoods wildlife species benefit.
We rely on the snow to tell us valuable information about our wildlife. Since 1977, trained animal track observers have traveled survey routes after a snowfall and recorded how many tracks they saw for bobcat, coyote, fox, fisher, otter, wolf, weasel, American marten and snowshoe hares. Initially, survey routes were set up only in about the top third of Wisconsin, but additional central forest counties were added in 1998. For each county, there are two locations with survey routes. Each route location had what was considered a good habitat mix of aspen, alder and conifers.
The survey routes were designed to be driven with a vehicle, so they are roads that were less likely to be plowed immediately after a storm. The best time of year to run these surveys was November or December. In years like this one, we might extend the survey period into January in hopes of having more suitable snow conditions. As we get later into January or early February, animals start to change from winter to spring activity patterns. This means they might be traveling less or hunting less as they find mates and select den sites to give birth and raise young.
During the winter of 2011-12, 24 survey routes were run. The conditions were poor or fair at best, so many routes either didn’t get run or provided very spotty information. The worst year in recent history was 2008-09, where only 20 routes were run. In an excellent year, like 2000 or 2005, 35 routes or more are completed.
The numbers gathered from these surveys do not tell us how many coyotes or otter we have. Each occurrence of a track is recorded, so we get a number of tracks observed per route. These numbers are compared against previous years and provide us with trends and relative information. For example, wolf tracks were added to the survey in 1998. At that time, 0.55 tracks were observed per route. Last year, 1.58 tracks were observed per route. This shows a trend of increased wolf numbers over the last 13 years. This trend agrees with our other population data. So, while roadside track surveys are one population management tool, like any other tool, they must be used properly to give us the greatest benefit. That is, if I get enough snow to run them.
To read these reports, check the website dnr.wi.gov, keyword “Wisconsin wildlife reports.”
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.