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Wintering - Not easy being the king (Whitetail Deer)

The undisputed “king” in terms of hunting respect and desire in North America has long been the whitetail deer. In terms of hunting licenses purchased, hunting equipment bought, and just about any other metric you look at... whitetails are the most desired quarry for hunters. With that in mind, the hunting population is always concerned with the status of the deer herd. Hunters read and watch videos and research these animals not only to become better in their pursuit, but also because they genuinely care about the health of the whitetail deer herd! When there are less deer around, hunters are concerned and want answers.

One of the major determining factors in the health of the northern whitetail deer herd is always the severity of the winters. In New Brunswick, where we are located, we are often said to be at the northern tip of the whitetail range and it is actually higher than their historical natural range. Whitetail deer are said to have existed in North America for close to a million years, but when Europeans first explored Canada, there were no whitetails in Nova Scotia and they were very few in New Brunswick. After this, human activities such as forestry and agricultural activities enabled the migration of whitetails farther northward (and westward).  Of course, deer adapt to fit their circumstances, but no matter how much they’ve adapted to their surroundings, severe winters can have a harsh effect on the population of whitetails in these areas.

Winter for a whitetail is a marathon battle to survive. It is not any single factor (cold, snow, predation, length of winter) that results in severe winter mortality rates, but rather the combination of these things that can have a terrible effect on the herd. In this northern range, if the cold and snow lasts a long time and the spring is delayed, numbers can be severely depleted.  Deer Biologists estimate that Deer are prepared to handle 120 days of snow on the ground.  As you can see, depending on when the first snow hits the ground, or when the last flake melts away in the spring is crucial to survival rates.

There are said to be 16 subspecies of whitetail deer in North America, and the one found in the northeast is one of the three northmost ones. Northern deer have a larger body size than the ones found further south, to enable them to survive our harsh winters. Their larger body size conserves energy better and enables larger fat reserves.

Whitetail deer in the northern climate will accumulate fat reserves under their skin and around their internal organs through the summer and fall, to serve as both insulation and as an energy reserve to help them to survive the difficult winter ahead. Biologists tell us that the fat reserves on an adult doe can be up to 30% of their body weight at the beginning of the winter.

The winter diet of a whitetail is low in protein and ranges from 50% digestable to undigestable. They will ingest things like hardwood and softwood twigs, needles, and bark. These foods only slow down their use of the fat reserves and some of the food intake in the winter actually burns more calories to ingest than the food will provide. As a result, deer will voluntarily reduce their food intake through the winter months. Death from malnutrition or starvation can occur if the winter runs long and fat reserves are completely used up before they can begin ingesting more nutritious foods as the ground thaws in the spring.

Doe eating buds in winter

Whitetails are remarkably able to deal with our cold winter temperatures through their biological makeup. This is because their grey-brown winter coat has hollow hair shafts and a dense, almost wool-like underfur. Biologists also tell us that they have special muscles that are able to adjust the angle of these hollow hair shafts to provide maximum insulation from the cold. Cold temperatures themselves do not devastate the deer herd, however the cold temperatures and especially the wind will accelerate the use of calories from their fat reserves in order to stay warm.

Snow, especially deep snow, presents many difficulties for whitetails. As the snow deepens, the most nutritious foods are covered and disappear, leaving only foods of marginal value for the rest of the winter. When snow is deeper than 40 cm, deer find it difficult to move around and will tend to follow established trails. The food that can be reached from these trails can get quickly used up, and will further limit their food intake over time.

Predation during the winter months also can contribute to high deer mortality. In the northeast, coyotes are the primary predator of deer during the winter months. They will group together into a pack and chase a deer to exhaustion, sometimes for days. If they can drive them off the established trails and into the deeper snow, the deer will have to expend more energy to break a trail through the snow.  A few years ago, we attended a whitetail deer seminar, in which we were told that while coyotes are not very efficient at actually catching deer, they’re incredibly effective at “the chase”.  Each time a coyote (or anything else) chases a deer out of their usual routine, more energy is utilized than would normally be required, and causing the 120 day figure we mentioned above to get shorter and shorter.  With this in mind, on many occasions when I am out on my snowshoes in the winter and come across a group of bedded deer which jump up and spook on behalf of me, I always feel that slight twinge of guilt at the potential energy wasted because of my actions.

With most things in nature, every downside comes with a slight advantage of another kind.  Having shorter legs than deer, coyotes are not able to navigate in deep, powdery snow which can actually have a very negative effect on coyote population. However, this advantage often doesn’t last for long. If at any time a rain or temporary melt happens, causing a crust on top the snow, coyotes can run on top of the snow and can be especially effective predators of whitetails. Beyond coyotes, sometimes domestic dogs that are allowed to run free will chase deer and contribute to their death, through the extra caloric use, expending their fat reserves. Dog owners need to be responsible in keeping their dogs monitored and managed to avoid this tragedy.

In order to slow down the use of calories from their fat reserves, deer will traditionally migrate to a wintering area. In some northern areas deer are said to travel as far as 60km from their summer range to a northern wintering area, but within 15km would be more typical. Their northern ranges are between 5 and 15% of the size of their summer range. In a winter range, they are seeking a sheltered area such as a dense softwood canopy that will intercept more snow and provide reduced snow depths and shelter from the bitter winds. These deer wintering areas are also known by the term “deer yards” as the whitetails are “yarding” or “grouping” together. Migration to these wintering areas offers them the benefits of many deer sharing a trail network to conserve energy as they seek food and seek safety from predators. One could think of this in terms that it is like several people snowshoeing together in deep snow. The first person must conserve a great deal of energy as they break the trail, but each person behind them has an easier and easier time to travel through the snow as the “road” has been established. This is not unlike the way deer travel on their familiar roads through their winter habitat. Probably because of the value of these trails, the larger wintering areas with higher numbers of inhabitants will provide a higher rate of survival.

A deer wintering area is a major key to survival in northern areas such as ours. In New Brunswick, the government manages over 800 wintering areas on crown land, with a total of over 280,000 hectares. The typical wintering area in our province would be spruce or fir stands with some cedar mixed in, with a crown closure (density of tree cover) of 50-70 percent. These deer wintering areas are critical for the benefits mentioned to whitetail survival through our harsh winters.

A discussion of wintering whitetails in New Brunswick would not be complete without at least a look at two of the biggest man-made pressures on their survival through the harsh season: habitat and food availability. In 2014, there has been a great deal of concern among hunters over the granting of logging rights to harvest some of the traditional old growth wintering areas in our province. A combination of factors have contributed to less and less deer using these areas, and as surveys have shown few whitetails in those areas, the companies asked and were granted permission to cut some of these areas. The concern lies in the fact that a mature wintering area takes around 35 years or more to have the proper canopy and density to enable deer yarding. Without them, critics say, the deer population will have no chance of bouncing back to the totals from years before.

Along the same lines, the lack of food can be a contributing factor in winter survival. During the summer and late fall the deer is trying to build up those fat reserves by eating highly digestible, nutritious foods. Through the spraying of herbicides, many tons of this “deer food” in forms of young hardwood shoots, bushes, leaves, berries are being killed and are unavailable to the whitetails. As a result they either cannot build up the necessary fat reserves or cannot find some of that browse during the early winter that they require for survival and end up perishing. In our recent interview with biologist Rod Cumberland he made it clear that he believes the biggest single contributor to our dwindling deer numbers over the past 30 years has been due to the widespread spraying of herbicides as a forestry management strategy. With what we know about the difficulties encountered by the whitetails through our harsh winters, we can easily see how much sense his stance makes.  This large-scale spraying of herbicides, along with the loss of habitat and deer wintering areas due to the use of mechanical harvesters are contributing to hardships in our deer herd. If something doesn't change in terms of habitat and food availability, we will never see the deer numbers of the early 80s. Even under ideal conditions, the carrying capacity and food availability is not there to support that growth of the herd.

Unfortunately many people, feeling they are doing a favour to their local deer population, participate in feeding programs to feed their local deer population.  We would be remiss if we didn’t do our part to discourage this habit.  As we mention, deer have adapted to their habitat, and human intervention often causes much more harm than good.  There are countless studies and reports, such as this one from Nova Scotia illustrate the challenges that come along with attempting to feed deer.  An entire series of articles could be written discussing the pros and cons of a whitetail feeding program, but we feel the best stance at this time is to advise our readers to avoid feeding deer.  We encourage people to focus on habitat improvement, and if they wish to feed deer in the winter they can do so naturally through cutting down a few hardwood trees in the area and effectively creating proper nutrition with plant life rather than artificially bringing in food.  QDMA is a fantastic resource for learning about managing your property to assist the wildlife throughout the year.

A severe winter can have the biggest effect on fawns, does, then adult bucks in that order.  Fawns use most of their caloric intake through the year just for growth, so they don't have the fat reserves that the adults have. Lactating does, especially those with two fawns, can be especially affected because of difficulty establishing the fat reserves needed. Bucks can sometimes use up a great deal of their fat reserves due to the fall rut, and then are forced to try to ingest as much food as they can before winter comes on in order to avoid starvation.  If a severe winter depletes the fawn crop resulting in low recruitment, this can affect the herd for many years.

Even a big mature whitetail is not immune to the challenges

This order of mortality runs counter to much of the opinions and articles you read, that promote the belief that bucks are more at risk than does of winter mortality. Biologist Rod Cumberland speaks to why this happens. “At DNR I compiled the age and sex of all deer lost to winter mortality factors (coyotes, starvation, ice injuries, etc.) – everything except roadkills. I found the actual percent losses during winter were: 50% fawns, 30% females, 20% males. If you read much of the recent literature about buck breeding habits in the fall of the year that Randy DeYoung has published, it helps explain this – at one time we thought the older bucks did all the breeding and ran themselves ragged in the fall. While a few bucks may exhibit this behavior, we know from research that ALL bucks get in on the breeding, and surprisingly, some large, mature bucks opt out entirely just to increase their odds of staying alive. Yearlings were in on 20% of the breeding, 2.5 years in on a bunch more. However, it did dispel the thought that all older bucks were doing all the breeding and running themselves ragged resulting in their age/sex cohort being the second most susceptible to winter mortality. Our NB data along with DeYoung’s research rewrote the thinking on this”

The combination of multiple severe winters in a row can really diminish the whitetail deer herd in our northern range. But these can be short-term changes as deer reproduce quickly. A few favourable years can allow the population to rebound substantially or even expand its range. According to the federal department of environment, a healthy herd is capable of almost doubling its numbers during a favourable year! Under favourable conditions, Hinterland Who's Who tells us that a female fawn tends to breed at 6-7 months of age and at 12 months will produce singletons (one fawn). A healthy, well-managed deer herd should see a bounce-back of numbers quickly if they get a few consecutive mild winters with high recruitment. The question has now become, “how well-managed is our deer herd?” How many deer could our forests now support? How many deer does the department of natural resources think is optimal for our province? 

2015-03-10 07:41:36


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