Land Management

Deer Dispersal

By: Dr. Jonathan Shaw

As a biologist and deer hunter I’ve heard it countless times, “Shoot the does because they’ll run the young bucks off.” While there are many reasons to harvest does, shooting them to reduce yearling buck dispersal is not necessarily one of them.

Dispersal occurs when a deer permanently leaves the area it was born in to establish a new home range elsewhere. Most dispersal in white-tailed deer occurs in bucks, and bucks typically disperse in the spring when they are roughly 1 year old, or just prior to peak rut when they are about 1½ years old.

While some research indicates that mothers harass their young and force them to leave, there are numerous studies that do not support this idea. Deer behaviors vary greatly with climate, habitat and herd demographics. Likewise, the timing, rate and cause of dispersal may differ from one population to the next.

In research we conducted at Chesapeake Farms in Maryland, we found no evidence that doe aggression caused yearling buck dispersal. We performed an orphan study using DNA and radio telemetry. If mothers forced their young to leave, non-orphans should be more likely to leave than orphans. We observed similar dispersal rates of orphan and non-orphan bucks, which indicated mothers were not causing their young to leave in this particular population.

We also observed interactions of radio marked yearling bucks with other deer. Again, we found no evidence that female aggression caused dispersal. However, we did observe an interesting trend in breeding behaviors of yearling bucks. Yearling bucks that eventually dispersed were involved in sparring activities earlier and more often that yearling bucks that did not disperse, which indicated breeding competition was linked to dispersal.

While doe harvest may not lead to decreased dispersal in young bucks, manipulating buck age-structure may. We observed fewer breeding behaviors in yearling males when numbers of mature bucks in the population were increased. The increased presence of mature males and their signpost likely suppressed breeding competition in young males. Hence, if breeding competition caused dispersal, and increased numbers of mature males suppressed breeding competition in young males, then an older male age-structured population should yield lower dispersal rates of young males. Our research supported this notion as we observed a higher dispersal rate of yearling bucks in a young male age-structured population (70% pre-QDM) than we did 7 years later in an older male age-structured population (54% post-QDM).

Dispersal is an important process that replenishes depopulated areas and ensures genetic diversity. Dispersal likely played a large role in successful white-tailed deer restoration efforts in the 20th Century, and it continues to serve as an important mechanism of exchange of genes between populations today. However, dispersal is a management challenge for most properties, because management success is largely affected by management practices on surrounding lands. While we may be able to decrease dispersal rates through harvest management practices, we can’t stop dispersal from happening, nor do we want to.

The best solutions to management challenges posed by dispersal are to 1) support regulations that limit buck harvest prior to and during the dispersal period. For example, the dispersal period at Chesapeake Farms ended early November, prior to peak rut. Hunters in Maryland were restricted to primitive weapons prior to and during this dispersal period, which permitted Chesapeake Farms to reach their QDM goals within a relatively short time. 2) Form cooperatives with neighbors in order to manage at a larger scale. Talk with your neighbors, inform them of your goals and involve them in management decisions and activities on your property. Your philosophy on how to manage deer may not match the philosophies of your neighbors, but that doesn’t mean you can’t work together towards a common goal. After all, most hunters share the same goal of being safe, having fun and managing for healthy deer. Use those commonalities to your advantage.

About the author: Jonathan received his Ph.D. from NC State University studying white-tailed deer mating systems and dispersal ecology at Chesapeake Farms, Maryland. As a District Wildlife Biologist for the NC Wildlife Resources Commission, he works with landowners to manage deer and other wildlife.

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