How Deer Deal with Winter Stress | Understanding Mature Bucks

It’s cold, there’s only sticks to eat, you’ve lost 25–30% body weight already and will be burning more calories each day than you are able to ingest. Sounds like a sarcastic blast, but it’s just another winter for Mr. Big and the rest of the deer. Here’s a closer look at what they endure and how they try to survive it.

This is Chapter 12 of Steve Bartylla’s free online book, Understanding Mature Bucks.

In the last chapter, I did a fairly poor job of trying to quantify how stressful the breeding phase and all it involves is on mature bucks. I also hopefully did just a good enough job to show those trying to manage deer, to the extent we can manage free-range deer, that there is absolutely nothing natural or healthy about overly tight buck-to-doe ratios. It makes for exciting hunting but at the cost of making all deer’s stress levels go through the roof, while being a living hell on Mr. Big.

Now, let’s start talking about something that is more easily grasped. That would be the stress that winter places on Mr. Big living in areas with real winters. For our sake, let’s say that means 6-plus inches of snow cover for one or more months of the year and worse.

Before we jump deeper, I should remind you all of my own limitations. I have done comparatively little work in the Deep South. Out of concern I could be wrong, I tend to hold my thoughts on southern deer. Here’s what I can say. In the hot, dry areas, summer is the southern deer’s winter. No, they don’t have 3 feet of snow covering most of the food. Instead, they have months with no rain and temps in the 90–100+, killing or turning dormant much of the plant life southern whitetails rely on as primary foods, while heat stresses the heck out of them. Southern deer don’t have winters, but they certainly do have their set of challenges. Even those southern deer living in swamps have gators to worry about, which no northern whitetail ever has.

Switching back to what I do think I know, remember, Mr. Big has just dumped 25–30% of body weight during the rut. For these deer, they’re also entering their seasonal low point of food, as no plant life I can think of is actively growing in frozen dirt and a whole bunch of mostly low-quality food is covered in snow. Outside of the rare standing cornfield or when a logging operation is going on in the area, deer in these settings are almost always left wanting for high-quality food.

Finally, one must factor in what Mother Nature is throwing at them. Deer have warm winter coats, but when the temps get in the single digits and below, it’s taking considerably more energies to heat their bodies, burning extra, precious calories they just don’t have to give. Same with busting trails through each new snowfall. It’s not that they can’t. It’s just one more precious energy drain.

Add it all up and most all deer in areas experiencing real winters run negative energy balances all winter long. What that means is that they are burning more calories each day than they digest. For does coming from healthy summer and fall ranges, rocking those copious layers of fat, no worries. Let Mother Nature throw her worst at them, as they are generally going to survive, ASSUMING they entered winter in great shape/with thick fat.

The fawns, well, they’re in trouble on bad years. As mentioned the other day, the pineal gland senses light in a 24-hour period and then sends the appropriate triggers out to the body to react accordingly. One of those things is to stop actively growing and shift near exclusively to fat building in early fall. It’s Mother Nature’s way of getting those fawns as tall as she can before winter (so they can reach higher woody browse and such), while stopping them just in time to build enough fat to hopefully survive winter.

Now, compare those fawns to a mature doe. They’re comparatively short (can’t reach as much food and it’s more work walking through snow), weak and small (small hurts as it takes more energy to heat one body unit the smaller the body). … Side note, this is the reason southern deer are smaller/northern deer are bigger. Smaller bodies expel heat more efficiently, which is key for those southern deer surviving summer, whereas larger bodies take comparatively less energies to heat, which is obviously better suited for northern deer. The fawns can’t get as much food and have to work harder to get it and need more for their size to heat their bodies. They’re in trouble on bad winters or when they enter winter in less than ideal shape, often due to poor habitat or poorly timed births.

You can lump Mr. Big right in there with the old, sick and seriously injured. He may not be old, compared to old does, but he is forced to pay for the sins of the rut, which transforms his body into an old deer. As the broken record keeps saying, he just lost 25–30% body weight, in less than two months, as well as likely having potentially deathly brawls. 

Simply put, the fawns, old, sick and hurt are what true winter claims first. Because of the rut and all that entails, each winter brings a close call to see what side of the line Mr. Big falls on, life or death.

Now, luckily, deer have ways of helping even the scales just a bit. First, in areas of true, seriously harsh winters, they gravitate to traditional overwinter yarding areas, often traveling many miles to get there. Though the yarding areas vary, they tend to have two things in common (at least the best ones do). They often are in slight bowls, so the topography helps block the wind, and have stands of evergreens with false roofs of branches. Pack enough deer in evergreens that allow travel under their branches, but offer a fairly low, false ceiling and it traps enough heat to make it as much as 4 degrees warmer in the yarding area. That may not seem like much, until one considers that the line between winter survival and death is a very, very fine line. The energies saved from just those 4 degrees can honestly be the difference.

Now, every area is different and all that true stuff, but one extremely troubling trend is occurring in very widespread areas. That is the destruction of these traditional overwinter yarding areas through logging and/or over browse. This is a really big deal.

No, this is unlikely to cause the whitetails to no longer be able to live in these areas. However, it’s an extremely safe bet that the destruction of these traditional overwinter yarding areas is resulting in dramatically increasing their stress levels (and their needle is already flirting with the red, when the quality of their yarding area is rocking) and making it so they simply can’t rebound as well or fast from bad years, as there is no doubt this is impacting fawn recruitment rates, which is what’s needed to build numbers back up from bad years.

One more thing on traditional yarding areas is that northern white cedar can be the ideal cover for this, as white cedar is the only browse species known that deer can survive exclusively on, all winter long. There are a bunch of high-quality browse species, but they all must be eaten with other browse species, as well (to both aid in digestion, as well as get all the nutrition they need). White cedar doesn’t need other foods to sustain deer and is being literally wiped out in many areas where it’s relied on for traditional yarding for deer.

I appreciate you all letting me jump on that soap box for a couple paragraphs, as this is a REAL big deal for a lot of northern deer. Quickly, in states like New York, old apple trees, often relied on heavily as overwinter browse, being continually crowded out by low-quality browse is also a serious issue, but that can be fixed by releasing (cutting the competition down around them) those apple trees.

For deer on the edges, where they get real winters, but just not as bad as those going to traditional yarding areas, they also often migrate some distance. The difference is that they tend to migrate to that clear cut regrowth, the logging operation for that winter, a standing cornfield or some other prime food source. In areas where deer don’t go to traditional yarding areas, they very often go for the best food they can find and set up shop there, for winter.

Deer have a miraculous ability to survive brutal conditions. Photo courtesy of Steve Bartylla.

Outside of those “migrations,” deer also greatly reduce their activity levels. In fact, they’re almost dropped to the point where travels revolve around getting to and from food, and that’s pretty much it. At the same time, deer are actually able to slow their metabolisms, further reducing their caloric demands by doing so. To top it off, they even often adjust their schedules, according to the temps. On the really cold days, even Mr. Big often shifts his feeding to late afternoon/very early evening, so they can be bedded during the coldest portion of the 24-hour period.

Think about that last line for a second and a bunch of stuff makes sense. When is it generally the coldest during a typical 24-hour period? Well, it pretty much generally keeps getting colder from sundown to just after sunrise. So, on the coldest days, Mr. Big has great incentive to feed that last hour or so of daylight on through the first few hours of dark, only to be snuggled in bed during the coldest portion of the day. That makes sense, as the line between life and death is very fine for Mr. Big, and every drop of energies he can save may be what gets him to spring.

At the same time, wow, can this knowledge be pure gold for hunting! Put just what we’ve talked about in this post so far together and there’s the answer as to why late season is the mature buck hunters’ secret weapon. In fact, many of the most serious mature buck hunters I know will take late season over the rut every day of the week. Personally, I’m in it more for the experience/observations. So, I like it all, but I completely get why so many others put all their eggs in the late-season basket. On those brutally cold days, the advantage finally switches to us, assuming you can pull off the hunt. (Going undetected and even just getting to full draw in late season is its own set of challenges, but Mr. Big can be ripe for the pickings.)

Does have another advantage for winter survival. Don’t ask me how, but enough biologists have told me that the doe is able to and does absorb a fawn when it gets really bad. If still bad after one she’ll absorb the second, if she has twins, and then the third, if she has triplets. I guess it’s nature’s way of first trying to get as many fetuses to spring as it can, but being willing to settle for the fawn maker, if nothing else.

Additionally, based on some truly gut-wrenching research, we also know that an adult deer can generally live for two months over winter without eating a drop of food. We even know that right around one month is the tipping point, where the deer will continue living for another month or so, but they are already walking dead; there is no coming back from the long-term starvation damage they’ve endured by not eating for a month, already.

Somewhat related, starvation browse is often hammered in areas with high deer numbers and low-quality habitat (often due in no small part to the overly high deer numbers). The reason it is called starvation browse is that it actually takes more calories to digest than they are able to get from the food itself. In turn, that junk food becomes a space heater, filling their stomachs, but not providing enough nutrition and even hogging space that digestible food needs, if that makes sense. Remember, deer’s first chamber of their stomachs is comparatively smaller than that of cows, goats and sheep. In large part due to that, cows, goats and sheep can digest foods that deer just can’t, which can result in deer dying of starvation with full stomachs.

As a final side note on all of this, we don’t want to try to stop deer from migrating to traditional overwinter yarding areas. Mother Nature hardcoded that into northern deer’s brains for a good reason. Those traditional yarding areas offer advantages that you don’t.

For the rest of us in areas receiving real winters, in my experience, absolutely NO improvement we can make will result in larger racks from year to year as well as offering a surplus of high-quality overwinter food. The better all of those deer come into spring the healthier and happier they’ll be come fall, and the racks on Mr. Big take dang good jumps, assuming they were nutritionally stressed and you can eliminate that. Remember, high-quality food doesn’t have to mean food plots. We can produce a ridiculous amount of quality food with a chainsaw, often putting money in our pockets in the process.

Read Chapter 1: Whitetail Tendencies

Read Chapter 2: Whitetail Home Ranges

Read Chapter 3: How Deer Use Core Areas

Read Chapter 4: When Core Areas Shift

Read Chapter 5: Seasonal Shifts

Read Chapter 6: Family Group Dominance

Read Chapter 7: Male Dominance

Read Chapter 8: Deer Population Dynamics

Read Chapter 9: Deciphering Deer Breeding Phases

Read Chapter 10: Big Deer Breeding Behavior

Read Chapter 11: Whitetail Rut Stress

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