Buckmasters Magazine

Deer Diets

Deer Diets

By David Hart

Knowing deer foods and eating habits can help you fill more tags.

There are about 4,000 native and naturalized plants in Alabama. New York has nearly as many species, and Florida has at least 4,200 different plants. Whitetails eat hundreds, if not thousands of them. From a hunter’s perspective, choosing a place to sit based on a food source can seem like an impossible task.

Don’t fret.

While deer often eat a dozen different plants in a day, they tend to be highly selective, choosing specific plants at specific times of the year. You don’t need to know every type of plant in your woods, but understanding deer diets and why they choose certain foods can help you fill more tags.

NUTRITION

“Deer select food based on availability, palatability and nutrition,” says University of Tennessee wildlife management professor Dr. Craig Harper. “They eat things that provide the nutrition they need at the time and that they can digest easily.”

Harper says deer seem to have an ability to choose foods based on nutrition quality as seasons and habitat conditions change. It’s a phenomenon most noticeable during periods of drought. Whitetails key on specific plants that meet their nutritional requirements when stressed.

Even in normal conditions, deer are selective about what they eat, says Dr. Marcus Lashley, a post-doctoral research associate with North Carolina State University. During the spring and summer, they focus on a handful of forbs, particularly plants with new growth.

“What they select can vary by region and the nutrient level in individual plant species in that region,” Lashley said, “but they seem to be pretty consistent in their choices. They will eat a variety of foods at any given time, but they definitely select specific plants much more than others.”

LEAFY GREENS

Lashley found deer routinely eat plants like greenbrier, strawberry bush, ragweed, beggar lice and pokeweed when they are available. Those and other forbs make up about 70% of a whitetail’s diet in the spring and summer. However, they don’t eat random parts of those and other plants; they select specific parts.

“They prefer the tender new growth like the tips of greenbrier vines, young, tender tree leaves and the new leaves on blackberries,” he said.

Plants like prickly lettuce, old field aster and catchweed bedstraw are high on their list during certain times of the year, Harper says, and they are particularly fond of blackberries. Whitetails eat the leaves everywhere the plant is found and virtually all year. Harper evaluated protein levels of blackberry leaves from around the country and during different seasons. Although they lose protein into the fall and winter, they remain a favorite food during the lean months.

“Crude protein levels [in blackberry plants] went from a high of about 22% in the spring to about 12% in January and February in areas where the plant continued to hold leaves,” Harper said, ”and it’s highly digestible, particularly the young leaves. Whitetails really like it.”

PROTEIN MATTERS

Whitetails don’t just survive on protein, but it is a vital part of the diets of lactating does and fawns, as well as bucks, which need high levels of protein for antler growth. They also need lots of calcium and phosphorous.

“The plants deer tend to select often have the highest levels of protein and other nutrients,” Harper added. ”In the spring, most plants meet those requirements, although there are many plants that have high levels of nutrients and are highly digestible that deer won’t eat. They are either toxic, or they don’t taste good to deer.”

Carbohydrates are as important in the fall as protein is in the spring and summer. Carbs help contribute to fat reserves, which aid in survival during leaner times in late winter and early spring. Corn is high in carbohydrates, which is why deer flock to it in winter.

NUTS OVER ACORNS

Acorns are loaded with carbs, too. They aren’t necessarily high in protein — for comparison, red oaks have a crude protein level of about 10.7% while crimson clover has 28% crude protein — but they are highly digestible and loaded with carbohydrates. Every deer hunter with a few years under his belt knows whitetails flock to oaks when acorns drop.

Not all acorns are created equal, and whitetails prefer white oak acorns over red oak acorns. That’s likely due to palatability, Harper said. Red oaks have more tannin, a bitter compound found in most red oak species.

However, the acorns of some white oak species – chestnut oaks, for example – have higher tannin levels than red oak acorns.

“They will eat chestnut oaks, but only if other species are not available,” Harper said.

Some wildlife managers have been promoting other oak species as an alternative to the two more commonly known species. Sawtooth oaks, for example, grow fast and produce an abundant acorn crop faster and more reliably than native red and white oaks. However, new research found that wildlife don’t eat them much. A study conducted by Lashley and others found that less than 1% of sawtooth acorns that fell to the ground were consumed by various wildlife species. Twenty-nine% of white oak acorns in the same study were eaten.

“Nothing touched [the sawtooth acorns] when we had a bumper crop of native acorns,” Lashley said.

Further, most sawtooth acorns fell much earlier; most in the study site were on the ground by early September, which makes them virtually useless as a place to hang a treestand. Dr. Christopher DePerno, the academic advisor for the study, offered another warning about sawtooth oaks.

“We have 20 or more native oak species,” he said. ”Why would we introduce a non-native species when the native oaks we have do a perfectly fine job of providing food for wildlife?”

When native acorns fall, they can make up 80% of a deer’s diet. That’s a pretty good clue how important they are, but don’t forget 20% of their diet still consists of other things.

FOOD PLOTS

That 20% is why food plots can be such a draw in the fall and winter, even when deer are eating acorns. They are even more important when the acorn crop is poor. Harper says a variety of common food plot plants are not only high in protein and other vital nutrients, they are highly digestible and attractive.

Again, deer select foods based on three things: availability, nutrition and palatability, which is tied to digestibility. Crimson clover and white clover both have high protein levels and are highly digestible.

In fact, virtually all of the food plot plants sold through places like Whitetail Institute, Pennington Seed, Tecomate and Mossy Oak’s BioLogic are great deer foods at one time or another. Deer might not eat a specific plant in October, but they will eat it eventually.

Brassicas and turnips are prime examples. Although the leaves are coarser later in the season, they are more attractive after a frost. The cold alters the composition of the leaf and increases the sugar level, making it more appealing and nutritious.

“Deer select what to eat in food plots the same way they choose their foods elsewhere,” Lashley said.

Deer won’t eat a plant just because it’s green, though. Cool-season perennial grasses like fescue and Bermuda grass might seem like they should attract deer, but those and other grasses are virtually ignored.

Harper says deer might eat perennial grasses some, but only the tender, young shoots. Most of those grasses are relatively indigestible and have low protein levels.

“If you see a deer feeding in a fescue field, it’s probably eating other plants growing among the grass,” Harper said. “They’ll eat a lot of plants, but it’s very unlikely they will eat perennial grasses.”

WOOD IS GOOD

As the season progresses and various forbs go dormant or stop producing new growth, whitetails switch primarily to browse. The tender tips of young trees and other woody plants can be high in nutrients. Thicker, coarser browse is not as digestible, but it can also meet a deer’s dietary needs.

Lashley, an avid deer hunter, says even when food sources are limited, whitetails remain highly selective. It might seem like they are randomly nibbling on the tips of low tree branches and shorter shrubs as they walk through the woods, but they are likely focusing on a few plant species. They know which plants provide the nutrients they need throughout the year.

ANYTHING GOES

Whitetails will eat just about anything in some regions, even if it is low in nutritional quality and difficult to digest. In extreme cases, they have little choice. Michigan Department of Natural Resources deer biologist Brent Rudolph says when deer in Northern climates eat spruce and fir needles, you know times are tough.

“It’s not unusual to find deer that have starved to death with a stomach full of spruce or fir,” he said. “There is some nutritional value in those plants, but typically not enough to sustain them over a prolonged period.”

Not all evergreens are bad, though. Rudolph says whitetails in northern Michigan rely on such things as white cedar and even white pine in late winter and early spring. Both have adequate nutrition to sustain deer during the toughest season. They will also eat the tips of branches from such trees as birch and red maple.

That doesn’t mean you should hang a stand over the nearest birch tree and expect to see deer. We all know it’s much more complicated than that. However, having an understanding of what deer eat and when they eat it will help make you a better hunter.

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This article was published in the September 2015 edition of Buckmasters Whitetail Magazine. Subscribe today to have Buckmasters delivered to your home.

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