Deer winter kill?

[Lee Lobbestael]

How ddep does snow have to be before you start worrying about winter kill concerning deer? I'm in southern michigan and this has never really been a concern but now we have about what looks like close to two feet on the ground and it got my obsessive compulsive tendencies bothering me in my head!

[NBK]

I'm worried here too.
We've had a "real" winter here for the first time in a decade with plenty of snow and sub zero temps the majority of December.
Tonight it's getting down to 34 below zero!
Add to that our abundance of wolves and coyotes and I'm wondering what our already low deer numbers are gonna look like next season.

[bofish-IL]

Illinois is having a lot of snow also. I would think it would effect deer that are hurt or in poor shape for sure.

Also I noticed a lot of fawns by themselves even early in the season. Since they don't have a doe to show them how to make it through a hard winter it might be harder on them.

[Lee Lobbestael]

Yeah no wolves here in the lower peninsula fortunately. I think they will be fine I'm just wondering what they eat in these conditions or do they just burn their fat stores

[Stumpkiller]

In the late 90's I found where five deer had laid-up under hemlocks and all passed away within 20 feet of each other.  We had many feet of snow on the ground at that time.

Any winter will take some.  A hard winter may take many.  It will be the smaller deer that can't dig down to the old grasses or have the body mass to keep warm enough through the cold snaps.

[Mojostick]

The Michigan DNR will start releasing their Winter Severity Index Report numbers soon. I'll post those numbers when they start issuing them to the public. It's actually pretty early to start looking for those numbers. It seems it's late Jan-Feb. before we see those released.

I'll list some of the factors used at the end of this post.

What usually gets the deer in trouble is most importantly, too many deer for the habitat. Imagine a terrible disaster involving people. Say there was a plane crash on a remote island and 200 people were cut off for 4 months. Now imagine there's only food enough to support 100 people for 4 months. The reality would be that in end that it wouldn't merely be 100 people that would starve to death. The real end result would be that about 150-175 would starve to death and the surviving 50-25 would be in terrible shape when rescued. And they'd be in rough shape for months. Poor antler quality is often a visible sign of this, due to button bucks having such a rough first Winter. Now imagine the same scenario where instead of 200 people with food for 100 that there were 100 people and food enough for 100. After 4 months, they'd still be in decent shape.

While the desire to see lots of deer is understandable, it's Winters like this that require biologists to attempt to keep deer herd numbers in check and balance. It's also why hunters need to do their part too.

Another major factor is the length of a tough Winter. Even if there's lots of snow early, it's not as bad if we get an early melt, like say in early March. It's when Winter drags on and on, that deer really drop in those final weeks. Luckily, our forecast for next weekend is around 38 and rain. Let's hope.

Another factor is unfortunately what we have now, extreme cold. Extreme cold zaps energy.

I realize that people have the need to "do good" and feed the deer, but sadly, all that does is dig the deer into a deeper hole. Feeding in Winter can throw the whole metabolism off and can keep already inflated herds too high. There are times when nature needs to do what hunters can't or won't.

On a side note, if one plants food plots, you may want to consider one not for hunting over but for Spring melt off. Coming out of Winter, a lush green Winter Wheat plot can really help your surviving local deer herd. Too many people think in terms of hunting when they think food plot. Instead, think "food" when you think food plot and think in terms of how it helps the deer put on fat, instead of how it may help you tag a deer. A lush green field in April sure helps out pregnant does/fawns and helps later antler growth. My two cents.

Here's how MDNR comes up with the WSI numbers. Sorry about the format of the paste...

Background Information
Deer are adapted to survive most Michigan winter weather conditions. However, research suggests that winter weather can affect deer mortality, fawn production, and deer physical condition (including antler development). Factors such as the quality and quantity of habitat types, deer population density, food availability, weather conditions of the previous summer, timing and duration of severe winter weather events, and timing of spring green-up affect the relationship between overall winter weather and the impact
on the deer population. Deer may also avoid the worst winter weather by moving to wintering habitat that provides shelter from wind and snow and provides food sources to maintain energy reserves to counteract the effects of low temperatures.
Although the exact nature of a winter’s impact on the deer herd can never be predicted, the Michigan Department of Natural Resources (DNR) monitors winter conditions by calculating a winter severity index (WSI). The WSI reflects the estimated effect of winter weather conditions on the energy reserves of deer; the higher the index
value, the larger the potential impact on the herd. More severe winters may require deer to expend more energy than they have available or may require the deer to use energy stores for survival rather than fawn or antler production. Using the WSI can help DNR biologists understand potential impacts of winter weather on the deer herd. The current WSI system takes advantage of standard weather data available from the National Climatic Data Center. The DNR uses weekly data on air temperature, wind speed, and precipitation from weather stations throughout Michigan and the
surrounding area in a series of mathematical equations to calculate a weekly index value from November through April. The WSI values from individual stations are averaged across the three regions of Michigan to give a regional perspective on winter severity. The DNR plots these values over time to provide insight into the pattern of winter severity over the course of the winter and to identify severe weather events.
Extended periods of severe weather and very early or very late peaks in severity tend to have the greatest effect on deer.
Due to the complexity of the relationship between the deer population and winter conditions, no single index can predict over-winter mortality, fawn production, or physical condition. Using the WSI as a tool to qualitatively evaluate winter weather severity, the DNR can identify winters that have the potential to severely impact the
deer herd. DNR biologists may also measure snow depth and make field observations of deer wintering areas to assess winter mortality and winter physical condition. The biologists use the WSI and their field observations along with a variety of other information to assess the deer population and adjust annual harvest quotas and make management decisions.

[Bonebuster]

A late spring is harder on them than an early bad spell.

The increased daylight speeds their metabolism and increases the need for calories in the spring.
A late spring reduces food availability when they need it most.

Harsh cold and deep snow is something southern Michigan deer usually don`t have to deal with too much. At least not for an extended period.

After this cold spell the forecast is for temperatures to moderate at least for a while, and that will help a lot.

Deer in the north are in for a bad time this year.
While I was at my place in Iosco County, the coyotes were travelling across the top of the crusted snow with ease. I spent the last three days of archery season hunting/calling coyotes instead of deer hunting. Coyotes did not respond to any calls and we found TWO fresh deer kills from coyotes. We posted over the fresh kills with .22 rifles and all the warm clothes we could muster.

I have been following the weather in Wisconsin and they have had some NASTY temps for an extended period.

Lets hope the weather moderates for the rest of the winter...get out and kill some coyotes, Southern Michigan has plenty of them!

[Jack Shanks]

I'm with Mojostick on the food plots. I planted 3 acres of winter rye on my property in northern Michigan late last summer in hopes that it would help the deer out in the early spring and not so much to hunt over. Actually, the deer had enough other food sources in the area that the rye wasn't a big attraction during the fall.

[NBK]

Mojostick,
Great post with alot of good info there.  Thanks for taking the time.

[Mojostick]

Here's some more info from MDNR. I'll get ahold of Brent Rudolph and see if he has any WSI numbers yet.

 http://www.michigan.gov/dnr/0%2C1607%2C7-153-10319-109131--%2C00.html

Monitoring Winter's Impact on Deer

Michigan winters can be tough on wildlife, including white-tailed deer. When the winter winds howl and snow whips across fields locking the landscape in an icy grip, deer in our northern areas seek shelter in conifer swamps where they likely will remain until March or April.

Wintering whitetails are remarkably adaptable animals, but our harsh northern climate claims some deer every year.

Winter severity has been measured by the Department of Natural Resources at field offices across the state since 1969. Initially it was developed to measure the stress winter weather placed on white-tailed deer, but since has been applied to other wildlife species.

The department's method of calculating winter severity incorporated a measurement of wind chill, snow compaction and snow depth starting in November and continuing until the end of April.

Each week, biologists would collect data from a chillometer (a device developed to measure the amount of energy required to maintain a pot of water at 39 degrees F.) and snow compaction gauge. Snow compaction and depth were measured by dropping the compaction gauge into the snow. The depth the compaction gauge sinks was recorded and added to the energy reading from the chillometer to produce a weekly winter severity index (WSI) measure.

The seasonal WSI then could be calculated by summing the values for each week. The number generated using the WSI procedure allowed a general comparison of winter conditions from one year to the next.

According to DNR Research Specialist Brent Rudolph, a review of historical data shows that winter losses appear highest when the WSI reaches a mark of 120 or more.

"But it's really not as simple as just labeling any given winter as harsh, moderate or mild," Rudolph said. "There just are too many variables involved."

As its name suggests, the WSI can only generally track the severity of weather conditions that may be stressful to wildlife and cannot be used to directly quantify impacts on wildlife populations.

Although useful, this method of collecting WSI measurements required regular equipment maintenance, absolute consistency in measurement by many different employees, and great travel times to some of the weather station locations.

So, beginning in 2005, Rudolph and other DNR biologists are using a new, automated method of determining winter severity, which eliminates some of the complications associated with the old method of WSI data collection.

The new method uses data collected at weather stations established and maintained by the National Oceanic and Atmospheric Administration. These stations collect data hourly and record the readings on the Internet. By selecting specific weather stations around the state, a WSI value (comparable to values collected in the past) can be determined.

The new WSI allows the same kind of general comparisons of weather conditions from one year to the next while reducing the time and resources required. The DNR now offers an online WSI Report that contains graphs showing progression of the WSI throughout the winter season (November through April) by region The graphs show the current year related to the average weekly regional WSI.

"Deer are well-equipped to survive even the harshest conditions during a 'typical' winter period," DNR Big-Game Specialist Rod Clute. "Their metabolism declines during the winter months, enabling them to conserve energy and rely heavily on fat stores during adverse periods or when the availability of food is limited."

In winter, Clute said deer instinctively seek protective cover in areas commonly referred to as "deer yards," to minimize body heat-loss and the hazards of deep snow.

"Because of a strong homing instinct, deer may travel distances of 40 miles or more to their traditional wintering grounds." Clute said. "It has little to do with the availability of food."

However, when severe conditions arrive earlier (November and December) or linger longer (April) than usual, winter mortality or poor fawn production the following spring can have a noticeable effect on deer populations in some areas.

Biologists, therefore, must balance future management recommendations with more subtle aspects of where and when harsh weather occurs, rather than simply using the general severity of winter conditions.