Shuffling along on snowshoes, I noticed the two-toed tracks in the snow merging into trails, which became more numerous and well-used as I drew closer to the big hemlock stand I was heading toward. Stepping off the power-line right-of-way into the forest, I felt the change as much as I saw it. It was an eerie feeling. The light was much dimmer and the air cooler under the dense canopy. It felt almost cryptic, yet this was a temporary bastion of life—the whitetail’s last stand against winter’s severity.
Winter survival for deer is a matter of economics and energetics. The goal is to maximize the cost-to-benefit ratio between energy gained and energy expended, yet the odds seem squarely stacked against them as benefits become scarcer and more energy is required to obtain them. Still, most manage to make it through the bottleneck of winter; and with a little help from us, they can not only survive but thrive.
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Simple body functions, like metabolism, burn energy. Deer must eat just to fuel these functions, but the very act of feeding uses more energy. You could consider that energy loss as overhead—the cost of doing business. Simply breaking even is not enough. Young deer need additional energy for growth, and mature deer still need to make a profit. Bucks use a lot more energy during the rut, and does need more for gestation. Unfortunately, Mother Nature plays a cruel trick, placing some of the highest energy demands on deer during a time when food is at its lowest in terms of both nutrition and availability, and environmental conditions are at their worst. It’s nature’s way of ensuring only the fittest individuals survive.
Let’s back up a bit on the calendar. In late summer, diminishing daylight triggers physiological changes in deer. Something hard-wired into their DNA prompts them to shift their diet toward high-calorie foods that provide more energy and allow them to lay on fat reserves. Both bucks and does are probably at their peak physical condition, with the greatest fat reserves, several weeks prior to the rut. The coffers are full, but some big expenses lie ahead.
The energy drain begins with scraping, rubbing, and sparring, and intensifies with seeking, chasing, and sometimes fighting over does. In addition to using more energy, bucks especially spend less time gaining it. This initial period of deficit spending can last a month or more, and bucks can lose up to 30% of their body weight. In other words, they’re draining the savings account right before the Christmas rush.
Post-rut is often referred to as a period of recovery, but deer never really recover fully during this time. For the rest of the winter, they’ll operate at a deficit, losing more energy and fat reserves than they can obtain. One reason is that natural food is lacking and of low nutritional value. In the absence of supplemental food, most deer feed largely on coarse, woody browse in winter. That takes more energy to digest and provides less nutrition (more on that in a bit).
All is not lost, however, as deer use several physiological and behavioral adaptations to survive winter’s severity. For starters, they move less to burn less energy. During sedentary periods, they can lower their metabolism by as much as 50% and may remain bedded for several days during severe weather events. All the while, they’re still burning valuable fat reserves just to stave off the cold.
They can further reduce energy loss by seeking protective thermal cover. In the Midwest and West, where cover is lacking, deer may use topography, seeking draws or bottoms, or finding a south-facing ridge side warmed by the sun. Further, east and north, softwood stands can protect deer from chilling winds and reduce snow depth, allowing for easier, more energy-efficient travel.
In the northern woods, deer often move—or even migrate—to traditional wintering areas or deer yards dominated by softwoods (see sidebar: Deer Wintering Areas). That protection comes with certain risks. Concentrating deer into smaller areas puts more pressure on the habitat, and over time, edible food becomes increasingly scarce. Concentrating deer also increases stress and the possibility of disease transmission, and it attracts predators. It’s a risky endeavor, but the potential benefits are greater and the costs lower than bedding in exposed areas.
Bruce MacQueen
It all seems like a pretty grim existence up to this point. Some deer will die—first the weak and the sick, then the oldest and the youngest. During exceptionally harsh winters, even healthy, middle-aged deer may perish, occasionally in massive die-offs. But some will survive, and there’s much that land managers can do to increase that proportion.
Let’s start with the low-hanging fruit (no pun intended), as that most directly affects energetics. The healthier deer are at winter’s onset, the better their chances of surviving through it; so providing high-energy fall foods is important. Regular readers of Gamekeepers can find more specific details, but in general, that means things like fast-growing annual food plots and mast orchards. The more variety, the better, as that widens the window and closes gaps in the nutritional calendar—not to mention keeping deer from wandering off. Providing soft and hard mast could be as complicated as planting mast orchards or as simple as releasing existing mast-producing plants by removing competition and allowing more sunlight to reach them. Some species, like plums and mulberries, will also form thickets that provide cover.
Even under the best conditions, deer will still use much of the energy you provide during the fall and will need food for recovery and holdover through the winter. This is where food plot crops like brassicas, corn, sorghum, and soybeans will help. Green vegetation is long gone, but beans, seeds, tubers, and bulbs may persist well into winter, depending on deer densities.
For those who grow agricultural crops, leaving some standing corn or beans can be beneficial. That brings up another point: deer seasons are set in the fall because this is the best time to thin the herd—before food becomes scarce. We all want more deer on the landscape, but the land can only support so many. If land managers aren’t meeting harvest objectives, they’ll end up with too many mouths at the table, and all remaining deer will lack nutrition.
Proper herd management involves more than just removing the right number of deer. It also includes balancing age and sex ratios. For a variety of reasons, maintaining more natural ratios can improve overall herd health. If does are lacking, bucks must expend more energy to find them and fight over them. If does are too numerous, bucks may burn more energy competing for them. Also, more does may not be bred during their first cycle. They may breed later, and their fawns will be born later, possibly too late to survive the next winter. A lack of older bucks might mean more inexperienced bucks disrupt normal breeding patterns. All of the above means extra energy costs.
Getting back to habitat, managing it for winter survival includes more than just providing thermal cover. One of the most effective and efficient methods for the landowner is timber harvest to provide more browse. Which species you cut is important, as deer are preferential feeders, but you need not be a dendrologist to figure that out. While it doesn’t hold true for all species, deer tend to prefer hardwoods with opposite leaves and branches, like maple and dogwood, to name a couple. If you’re still not sure, let the deer show you—look for evidence of browsing, and which species are getting the most attention. Favor those and eliminate species they ignore.
To this point, I haven’t mentioned true supplemental feeding, but it’s certainly a viable option until your food plots and mast orchards are up to production. Corn is popular but can actually be harmful if not used correctly (see sidebar: Corn Conundrum). A better option might be a mixture of corn, grain, and seed, pellets, or blocks, especially those designed for deer.
In addition to fiber, these feeds provide digestible energy, degradable protein (DP), undegradable protein (UP), and minerals for replenishing body stores.
Conclusion
Think of your land as a portfolio. More aggressive investments like annual food plots might pay big over the short term but you should also make sure to invest in conservative, slow-growth assets like winter food and cover so your assets can withstand, periods of recession. Fortunately, it’s an annual cycle of boom and bust, but the less of the latter, the better.
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