Food and feeding habits
- Deer eat a wide variety of plants, but their main food item is browse—the growing tips of trees and shrubs. In late winter and early spring, deer eat grass, clover, and other herbaceous plants.
- Deer also eat fruit, nuts, acorns, fungi, lichens, and farm and garden crops if available.
- For their first few weeks of life, fawns thrive on milk, which is more than twice as rich in total solids as the best cow milk.
- Deer eat rapidly and, being ruminants, initially chew their food only enough to swallow it. This food is stored in a stomach called the “rumen.” From there it is regurgitated, then re-chewed before being swallowed again, entering a second stomach where digestion begins. From there it is passed into a third and then a fourth stomach, finally entering the intestine.
Shelter and range needs
- Deer are sometimes referred to as “edge” species, meaning they thrive at the interface of openings and cover patches. This allows deer to feed in productive openings while being close to escape cover.
- Many wooded suburban environments, such as parks, greenbelts, golf courses, and roadsides, meet the needs of deer.
- Mule deer can move long distances during spring and fall migrations to avoid mountain snow. Mule deer summering in the Cascades migrate as far as 80 miles to reach adequate winter range.
- Black-tailed and white-tailed deer normally reside within a ½ to 3 square-mile area; in mountainous locations, they move to lower elevations for the winter.
Reproduction and family structure
- Deer breed during a rutting season that normally occurs in November and December. Bucks compete for the right to breed using ritualized posturing and movements, and occasionally through intense fighting.
- Unlike elk, deer bucks do not herd groups of females; however, a single mature buck may breed with several females.
- Pregnancy lasts 180 to 200 days. Younger does give birth to one fawn, while does three to nine years of age and in good condition often have twins. White-tailed deer will occasionally have triplets.
- Newborn fawns nurse soon after birth and can walk on spindly legs almost immediately.
- Adult bucks take no part in raising fawns, and generally remain solitary or form bachelor groups throughout the summer.
- Family groups usually consist of a doe and her fawns, and sometimes her fawns from the previous year. Occasionally, groups of several does may be seen together.
- In winter, deer may be observed in larger groups of 15 to 30, usually grouping because they are concentrated in limited winter habitat.
Mortality and longevity
- Cougars, bears, coyotes, and domestic dogs prey on adult deer; young fawns fall victim to these species as well as to eagles and bobcats.
- Hunting, vehicles, and diseases all take their toll on deer. In many deer populations, hunting dampens the effects of other mortality factors; as hunting mortality decreases, other forms of mortality tend to increase, and vice versa.
- Few deer live longer than ten years, and most live for no more than five.
All about antlers
Male fawns develop buttons (small bumps on top of the head) at six to eight months of age. These buttons are the rudimentary beginnings of the young buck’s first antler set (Fig. 2). Just before the fawn’s first birthday, these velvet-covered buttons begin to elongate, growing from bony extensions of the skull known as pedicels. By September these first antlers are fully grown spikes, or small, forked antlers with two points.
Each year, the antlers tend to grow in mass and diameter. Older bucks tend to have more antler points than younger bucks, but the number of points is not a reliable indicator of actual age. Antler size and conformation also respond to nutrition, and thus serve to advertise the physical condition of the buck. Rich feeding in captivity has produced five-point antlers on yearlings, while a meager food supply can limit even dominant bucks to forks. Bucks generally attain adult-size antlers when they are four to five years of age, but the size and weight of the antlers may continue to increase each year until age ten.
Antlers serve to establish dominance hierarchies among bucks. Big antlers, like bright feathers on male songbirds, are an example of fitness evolved through sexual selection. Because large antlers mean a buck has either survived many years, has superior genetics, or uses high-quality areas, bucks with large antlers make good sires for a doe’s fawn. Does tend to select dominant bucks with large antlers for their mates, and this selection enhances the success of bucks with large antlers even more.
Bucks carry their antlers through the fall, dropping them between late December and early March. Hormonal changes cause a weakening of the bone at the tip of the pedicel, where the antler-growing center is located, and the pedicel/antler connection eventually becomes so weak that the antler separates and falls from the pedicel.
Most antlers that have been on the ground for more than a few weeks will show considerable signs of gnawing by smaller animals, and after a year most of the antler points will have been considerably shortened by these mineral craving critters. Dropped antlers are chewed by mice, rats, squirrels, hares, and porcupines, helping them to sharpen their front teeth while supplying them with calcium, phosphorus, and other minerals.