Indexing winter’s impact

Temperature, snow depth are key factors in deer survival

By DENNIS APRILL,  Outdoors Columnist

If a hunter or just a plain old deer lover asks, "How’s the winter going?" it is usually in reference to these economically important animals who are close to their northern limit of range in the North Country. 

For a deer to survive a normal northern New York winter, that animal needs to have put on adequate fat during the fall. And even if winter food supplies aren’t top notch, a deer can survive if it is not over stressed. But just what constitutes undue stress?  Attacks or being hounded by coyotes, domestic dogs or bobcats certainly would be examples; however, the real deciding factor is always the winter weather. So how can we judge the impact of a particular winter on our deer herd? Is there a formula that works? Actually there are two used in the Northeast. This week I will describe the system used in northern New England (except Maine) and the Upper Midwest. Next week I will examine the New York system. 

In the current issue of the Outdoors (formerly Vermont Outdoors) magazine, writer and licensed guide Francis Smith describes the system used in Vermont called the Winter Severity Index (WSI). From November 1 through April 15, snow depth and minimum temperature are recorded in various parts of that state. One point is given for each day that has a below-zero reading and one point for each day the snow depth is over 18 inches. The cumulative totals for each season are broken down in the following categories:  0-50 points — mild --very little deer loss 57-80 points — moderate --minor fawn losses, but still good spring fawn numbers 81-100 points — severe --moderate fawn losses, minor adult losses, some reduction of spring fawns 100+— very severe--heavy fawn losses, moderate adult losses, poor spring fawn crop I have kept daily weather records for the past 25 years, as much a hobby as anything else. Earlier this week I decided to apply the WSI to my home area. Here’s what I found. In the winter of 2000-2001, I recorded 102 WSI points, an indicator of the severity of the winter; however, 43 percent of those points came from early March until April 15. By this date, Feb. 10, last year I had more than 40 points. 

In contrast, for this winter I have so far recorded only 10 WSI points — seven of them coming in the past week when my snow cover exceeded 18 inches. The season total is no surprise because we are having a mild, dry winter so far. There are, however, variables that must be considered. 

One is snow crust. 

Though my snow depth out front is about 20 inches, the snow pack has a crust not strong enough to hold a deer,  but it can support a bobcat and some smaller coyotes. Another thaw,  some rain and a refreeze will make travel harder for deer and easier for predators. 

Another factor is location. I am situated at 1200 feet in elevation in the peripheral Adirondacks, far enough away from Lake Champlain’s moderating influence that keeps snow depth down in normal winters. In places like Keeseville or Champlain, for example, the WSI points are almost assuredly lower than where I live. Farther out west in the central mountains, I’m sure the WSI points were much higher in 20002001 than mine were, so it is not surprising the yearling buck take was only 26 percent in the mountains last fall,  an indication of substantial losses during the previous winter. 

There are other local factors that play a role as well. I generally have more snow cover than my neighbors because of the way my house is situated. Deer as close as a half mile away might be experiencing different conditions If nothing else, the WSI helps us put things in perspective, and in some cases verify our hunches. If deer are having problems with cold and snow, then certainly life is more difficult for humans who have to live and travel in those conditions. So far, we’ve been in a mild trend, and I, for one, hope it continues. 

• Weather Data: After April 15, I will give you my final calculations. If anyone out there has also kept daily temperature and snow depth records, I would like to hear from you to compare notes and possibly publish some of the findings from the various geographical zones that make up northern New York. 
• License glitch? If the new license fees and regulations are passed by the state legislature this year, there is one interesting change that may affect how hunters buy their licenses. 

A deer hunter in the Northern Zone with the new Super Sportsman license,  if he or she has all the prerequisite safety certificates, or if the hunter has a Big Game license and Archery and Muzzleloader tags, will be able to take three deer, normally one during the Regular Firearms, Muzzleloader and Archery seasons. 

However, as the law is now written,  you need not be an active bow hunter to take the third deer. The Archery tag will also be good for a hunter using a muzzleloader during the Muzzleloader season as well. 

I imagine the Archery Safety classes will increase in size when the new law takes effect.