What’s Killing Your Whitetails?

Stress from insects, heat and humidity can harm whitetail deer in summer.

Those aggravating mosquitoes biting in the evening when you’re relaxing in the yard or trying to fish a few hours or the ticks and chiggers that await on the work days at the deer lease are minor aggravations compared to what deer go through.

Deer are bugged, quite literally, by critters from spring through the first cold spell and frost. Mosquitoes, ticks, midges and different flies all give deer fits. Check out this great information from veteran hunter and researcher Charles Alsheimer about what white-tailed deer go through each summer, from the smallest fawns to the oldest bucks.

The stress that heat and insects can place on whitetails can be a major problem during spring and summer, and even further compounded when their habitat is poor.

By Charles J. Alsheimer

The stress heaped on white-tailed bucks in the depths of a Northern winter can be terrible. But as bad as cold, deep snow and a scarcity of food can be, the stress a buck encounters in summer can rival anything it receives in winter.

By mid-July, many stressors begin affecting bucks. Two of the biggest factors are heat and insects. High humidity also takes a toll in some areas. When heat and humidity arrive, a white-tailed buck’s life becomes miserable. Plus, the high temperatures often are accompanied by an unbearable onslaught of insects. These insects can actually kill a buck or stress him enough to weaken his immune system.

Seeking An Escape

During periods of excessive heat and humidity, I’ve counted more than 200 flies on a buck’s body at one time. This causes deer to be in a state of perpetual motion. They constantly twitch and shake their heads to rid themselves of pests.

Such activity will wear down a deer, and the bites incurred often cause minor bleeding and even infection. To escape flies and other insects, deer will retreat to stream beds or the lowest, thickest point in a forest — where air temperatures can be as much as 15 to 20 degrees cooler than in open, sun-drenched areas.

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I’ve also seen a situation where a buck’s antler velvet was cut and egg-laying flies were attracted to the wound. Maggots grew and fed on the bloody antler, eventually killing the buck. Although rare, this is another example of the different types of stress whitetails can face during the “dog days” of July. Only when late August arrives with its cooler days and nights do whitetails get some relief.

The stress that heat and insects can place on whitetails is further compounded when their habitat is poor. Without proper nutrition, the stresses of summer can lead to many additional problems for whitetails, with one of the greatest being disease.

A Day in the Life

Dawn comes early for a buck in July, and if humidity is not high, he will feed one last time when the sun hits the horizon. With temperatures 20 to 50 degrees cooler at sunrise than mid-afternoon, the stress of heat and insects are at a minimum. Life is good for a buck at this time of day, but things are about to change.

Ticks also may pose a problem for deer.

Before the first hour of daylight passes, the buck gravitates to the coolest location he can find to bed. He knows shady areas with high grass and thick brush near streams will provide him the most protection from the heat and insects that will hound him throughout daylight.

By mid-morning, the temperature rises, and harassment from insects begins taking a toll on the buck. As mercury inches up, insects buzz around his eyes and body. In an attempt to ward them off, the buck shakes his head, flaps his ears and twitches his body incessantly.

It’s a losing battle, and he knows it. With flies biting him all over his body, the buck bolts from his bed and runs off with a fog of insects in tow.

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When the buck feels separated from the insects, he seeks out another bedding location. Unfortunately, within minutes of bedding, the buck begins attracting more biting insects.
When the last two hours of daylight arrive, the buck has changed beds several times. Hungry and exhausted from the effect that heat and insects have had on him, he looks forward to the break nightfall will provide. Night is the buck’s best friend, and he knows the dark hours are cooler and that fewer insects will be active.

Throughout the night, the buck beds close to his prime food source and feeds heavily every three to four hours. During this time, he interacts with other bucks that use the same feeding area. He builds a bond with these other bucks, forming a loose-knit bachelor group. Although the buck seldom beds with other members of the group during daylight hours, he seeks their presence each night.

About the time the first hint of daylight can be seen, the buck rises from his nighttime bed one last time to feed before heading for daytime cover. His daily cycle is nearly complete as the sun inches toward the horizon.

With a full stomach, the buck vanishes into thick cover to prepare for another day of coping with July’s heat and the army of insects.

— Charles Alsheimer is Deer & Deer Hunting’s contributing editor of deer behavior.

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