Whitetails on the Move

Spring for one-year-old whitetails is like graduation for high school seniors - a time to strike out on their own. Like high school graduates, some will take off for far away places and some will establish themselves just up the road from their parents.

Missouri whitetails are truly mobile critters. The deer you see on the back 40 today may or may not hang around until next year. A high percentage of young bucks leave each year but are replaced by bucks that have dispersed from somewhere else. Some young does leave too.

Adult does and their offspring sometimes make significant spring and fall movements to areas with better food and cover resources. Adult bucks have finished their dispersals but still do a lot of moving during the fall breeding period.

Dispersals, migrations and breeding movements may increase mortality rates for these wandering whitetails because they are entering territories they are not familiar with. Some will be struck by vehicles or suffer similar accidental deaths. The urge to move is strong though. It is how deer and other animals colonize new areas and mix the genetic pool and is the reason deer sometimes end up in some pretty unlikely places.

Among whitetails most dispersals occur from April to June and involve yearling deer, although some males will wait until they are 18 months to disperse. Migrations occur during spring and fall and involve both sexes and all age classes.

Deer biologists and managers have long been interested in deer movements. Knowledge of daily and seasonal deer movement patterns provides important information that aids deer management. The first real means of studying movement came with the development of the radio transmitter in the 1960s. Attached to a collar placed on a deer, the radio transmitter allows biologists to track deer movements. Since the development of radio telemetry systems, numerous studies of deer movement, including several in Missouri, have been conducted. Missouri studies using radio transmitter collars suggest that the often quoted statement that deer spend their lives within a few hundred acres may not be true, especially in the northern agricultural parts of the state.

Deer biologists describe the area over which a deer moves as its home range. Home ranges will vary depending on the time of year and the sex and age of the deer. For example, adult bucks during the fall breeding season generally have the largest home ranges, often covering a couple of square miles. On the opposite extreme, adult does with young fawns have home ranges less than 100 acres during the summer.

Seasonal or permanent movements of deer outside of their home ranges are common. These movements can be categorized as dispersals or migrations. Dispersals include permanent movements away from an established home range. Migrations include movements to and from established winter and summer ranges.

In a deer study conducted in north central Missouri, we found that 77 percent of the buck fawns dispersed in late spring when around one year of age. The average distance these young bucks dispersed was nine miles.

Dispersal movements by young males are common throughout the animal kingdom. No one knows for sure what causes a deer to leave its home area, but social pressures and habitat probably influence rates and distances of dispersals. Dispersals are more common in dense deer populations and tend to be longer in areas of limited habitat.

Some theorize that aggression by the doe about the time she is ready to give birth may drive fawns away. Others suggest that there is an "internal" driving force that causes these young males to leave home so that problems associated with inbreeding are avoided. Whatever the reason, that buck fawn you saw while hunting last fall probably won't be around your place next season. Also, the yearling buck you shot this year may have been born miles away.

Besides movements by young bucks we also found that 21 percent of older bucks, mostly 1.5-year-olds, dispersed. Unlike buck fawns, most of these dispersals occurred during the fall and averaged around 13 miles. We think these movements are in response to the breeding season, when there is much competition for mates and a lot of aggression toward younger bucks by older, dominant bucks. Generally, a buck establishes a permanent home range by two years of age and will remain within that home range for the rest of his life.

In our north Missouri study, we also found that a small percentage of fawn females dispersed (16 percent). The average dispersal distance was similar to that of fawn males, although one young doe moved over 90 miles and was eventually taken by a hunter in Iowa. Her movement began during spring and she wandered north throughout the summer and fall.

Most young females we studied did not disperse but remained in the vicinity of their mother, even after the older doe had given birth to young. The young doe typically rejoined the dam (mother), forming a family group.

The family group is a typical social arrangement for does and buck fawns. Common fall-winter groups include four to six deer composed of a matriarchal doe, her fawns from the current year, her doe fawn from the previous year and any fawns she may have had.

In some parts of the Midwest, however, especially where deer habitat is limited and agricultural activities dominate the landscape, a high percentage of does disperse at around one year of age, just like male fawns. Lack of cover may force these young does to move.

Migrations of yearling and adult bucks were uncommon, but around 12 percent of the fawn and adult does migrated to and from winter sites. These migrations may be more common during severe winters, when deer concentrate on areas with an abundance of food and cover. These "yards," more common in northern deer ranges where winters can be severe, may hold high concentrations of deer.

People often report 50 or more deer in fields with abundant food and become concerned about an overabundance of deer. Often, however, they are seeing deer from many miles around concentrating on one area. In spring, these concentrations break up with deer migrating back to their summer ranges. Deer truly are mobile animals.