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Whitetail Jiu-Jitsu
12-13-2010, 08:23 PM
With the 5th highest snow fall of 17 inches here in MN and negative degree temperature to follow so early in the winter got me thinking. We all know that deer have a harder time living in deep snow and cold weather hurts any living creature.

But, how much does it actually play on their winter survival rate? Is anyone familiar with any studies done on annual snow fall compared to annual winter survival rate? Or subsequently, any studies done on the annual temperatures and the winter survival rate.

Does anyone have any insight?

MattRoss
12-14-2010, 11:36 AM
Whitetail Jiu-Jitsu,

This topic has been throroughly studied the past several decades - and today many state agencies tie their estimates of winter mortality back to this research. Often, it incorporates the Winter Severity Index (WSI) of that local area.

In short, in most areas of the north deer go into winter with a 90 day "clock" of fat reserves; if severe winter (based on some pre-determined WSI level) lasts longer than that clock, you start losing deer. Adults get as much as 50% of their daily nutrition from that reserve bank, fawns get about 25% since they are smaller. Deer survive winter (in the north) by balancing the energy they receive from those fat stores and whatever winter food they can get, against their daily energy costs.

Perhaps one of the first people to look at this topic was Dr. William Mautz from the University of NH. He wrote a peer-reviewed article in 1978 in the Wildlife Society Bulletin about the annual fat cycle in deer (Vol 6: pgs 88-90). In fact, if you were in a member in 2002, Kip Adams profiled this research in a feature article in Quality Whitetails magazine in the Winter issue that year (back when we did 4 issues a year).

Other big names of this type of research include:

Ozoga and Verme from MI,
DelGuidice from MN,
Moen from NY
Hobbs from CO
Gray and Servello from ME
Pekins and Thomson from NH

Hope that helps!

Matt

Side Hill Growler
12-14-2010, 06:46 PM
Here in Maine the biologist told me that he figures 100 days with a snow pack over 12 inches would result in high losses.

Whitetail Jiu-Jitsu
12-15-2010, 09:38 PM
Matt

Thanks, I found this which is very applicable to my area.

http://www.dnr.state.mn.us/volunteer/sepoct09/bounce_back.html

Younghunter
12-16-2010, 02:30 AM
Sandbur posted that study awhile ago on the forum. I thought it was very interesting!

If my memory holds... In the winter of '96-'97 the WDNR estimated that something like 160,000 deer died due to winter mortality in Northern Wisconsin. That was estimated to be about 30 percent of the overwintering deer population in those areas.

-Matt

foodplotdude
12-16-2010, 08:08 AM
Matt

I wonder if the reserve bank in bucks is stronger or depleats with the riggors of the rut? Several of my farms here in Maryland have a relatively balanced sex ratio and the ruts have been extremely strong the last few years and bucks literally run themselves to skin and bones. Couple that with last years brutal/multiple 25" + snow falls with blistering cold temperatures and we found plenty of what we believe were victims of winter mortality.....mostly bucks. Just curious if this might play a small factor in this.

sandbur
12-16-2010, 09:16 AM
WJJ-So far the center of the state and north have escaped much of the worst. For you and the southeast, the racks will be smaller next year.

Numbers will be down like we experience in northern Minnesota many years. You probably have many winters like that.

NH Mountains
12-16-2010, 10:20 PM
Matt

I wonder if the reserve bank in bucks is stronger or depleats with the riggors of the rut? Several of my farms here in Maryland have a relatively balanced sex ratio and the ruts have been extremely strong the last few years and bucks literally run themselves to skin and bones. Couple that with last years brutal/multiple 25" + snow falls with blistering cold temperatures and we found plenty of what we believe were victims of winter mortality.....mostly bucks. Just curious if this might play a small factor in this.

In the northeast the rigors of the rut is a major reason (besides coyotes) the mature bucks don't make it through rough winters. Especially if the snow comes early and doesn't give them a chance to gain back fat reserves.

Younghunter
12-16-2010, 10:33 PM
I wonder if the reserve bank in bucks is stronger or depleats with the riggors of the rut? Several of my farms here in Maryland have a relatively balanced sex ratio and the ruts have been extremely strong the last few years and bucks literally run themselves to skin and bones. Couple that with last years brutal/multiple 25" + snow falls with blistering cold temperatures and we found plenty of what we believe were victims of winter mortality.....mostly bucks. Just curious if this might play a small factor in this.

I'm sure it plays a factor for the buck moralities... but I always understood it in an opposite way.

When the sex ratios are skewed so badly that does are not bred in their first estrous cycle, then they enter a second estrous cycle a little less than a month later, and may enter a third estrous cycle if they still don't get bred. The added months of rutting activity causes more stress to the bucks than if the sex ratio was tight and all the does were bred in their first estrous cycle.

At least that's how I've understood it.

-Matt

sandbur
12-17-2010, 08:52 AM
I'm sure it plays a factor for the buck moralities... but I always understood it in an opposite way.

When the sex ratios are skewed so badly that does are not bred in their first estrous cycle, then they enter a second estrous cycle a little less than a month later, and may enter a third estrous cycle if they still don't get bred. The added months of rutting activity causes more stress to the bucks than if the sex ratio was tight and all the does were bred in their first estrous cycle.

At least that's how I've understood it.

-Matt

This was somewhat discussed this summer. BSK made a post that the rut pretty much occurs on time in the the north country , regardless of buck/doe ratio.

In the northwoods, I just almost never see a doe in a late heat. Most get bred on time during the first cycle. In central Minnesota and ag country, I can remember one doe fawn having a heat after the primary rut.

Matt, that is the way I had understood it. I no longer buy the argument for the buck to doe ratios we have in my parts of Minnesota.

sandbur
12-17-2010, 09:17 AM
I know we are stealing WJJ's thread.

Maybe Matt Ross can help us out on this. What would be the best tree species to drop if one wanted to help the deer through the winter? What browse has the best nutritional content and probably the least timber value if one was going to drop it just for the deer? The answer will vary with the cliamte and properties.

A winter harvest of timber would be the best.

In the late '60's, the old Minnesota Conservation Department told us to drop white birch on the state and county lands during the winter. White birch had little timber value and would sprout back form the stump for browse. Most birch trees we dropped were browsed back to 1/4 inch diameter stubs or thicker.

Perhaps Matt Ross could supply us with a list of preferred nutritional browse. We each dould decide what species we should cut on our properties.

Whitetail Jiu-Jitsu
12-17-2010, 10:21 AM
Don't worry about it, I already got what I wanted. All of the additional information is just gravy.

Wayne
12-17-2010, 10:49 AM
I know we are stealing WJJ's thread.

Maybe Matt Ross can help us out on this. What would be the best tree species to drop if one wanted to help the deer through the winter? What browse has the best nutritional content and probably the least timber value if one was going to drop it just for the deer? The answer will vary with the cliamte and properties.

A winter harvest of timber would be the best.

In the late '60's, the old Minnesota Conservation Department told us to drop white birch on the state and county lands during the winter. White birch had little timber value and would sprout back form the stump for browse. Most birch trees we dropped were browsed back to 1/4 inch diameter stubs or thicker.

Perhaps Matt Ross could supply us with a list of preferred nutritional browse. We each dould decide what species we should cut on our properties.

Red/Soft Maple is the best and highly preferred by deer. It too sprouts back from the stump, and in most northern states is the predominant species in the forest and has a moderate timber value.

Younghunter
12-17-2010, 02:17 PM
This was somewhat discussed this summer. BSK made a post that the rut pretty much occurs on time in the the north country , regardless of buck/doe ratio.

In the northwoods, I just almost never see a doe in a late heat. Most get bred on time during the first cycle. In central Minnesota and ag country, I can remember one doe fawn having a heat after the primary rut.

Matt, that is the way I had understood it. I no longer buy the argument for the buck to doe ratios we have in my parts of Minnesota.

Yeah, I don't know how much variability there actually is. I know some years I'll see fawns that are significantly different in size from the norm and that leads you to the opinion that one set was born quite a bit later than the others.

I think for the most part, our buck to doe ratios have tightened statewide after years of actually allowing antlerless harvests and in many seasons putting significant pressure on antlerless harvests. Maybe the buck to doe ratios were having more of an effect on the rut in the 80s and early 90s before we got serious about antlerless harvests. I don't know... I certainly don't have any data or observations to support that.

For the doe fawns... I think the norm is for them to come into heat later than the mature does, right?

Red/Soft Maple is the best and highly preferred by deer. It too sprouts back from the stump, and in most northern states is the predominant species in the forest and has a moderate timber value.

I agree with that. Soft Maples are excellent browse and they respond well to cutting. I've been planting them for a couple years now for that purpose... I plan on keeping them cut back for browse.

-Matt

sandbur
12-17-2010, 09:36 PM
I believe the doe fawns come in heat later than the older does. There is a gradient across our state from practically no doe fawns bred in the north to perhaps 2/3 bred in the southeast part of the state.

I hunt the ag belt in the middle of the state and more of a woods area a bit further north. Seldom do I see a fawn in heat in either location.(Maybe because we like to eat them!)