The Genetics of White Tailed Deer

Tremendous advances in molecular genetic techniques were achieved in the past decade.Wildlife researchers have benefitted from the progress made in both the theoretical aspects and "nuts-and-bolts" technology, such as the automated analyses developed for the recently completed human genome project. As a result, large-scale genetic examination of free-ranging wildlife populations is now feasible. The number and type of genetic markers available enables researchers to study patterns of genetic variation at several spatial and temporal scales. Microsatellite DNA markers are especially useful because they are highly variable, which is necessary for fine-scale genetic research.

In recognition of the beneficial impact of molecular genetic techniques to wildlife management, the Department of Wildlife and Fisheries and the Mississippi Department of Wildlife, Fisheries, and Parks began a cooperative research effort with the Samuel Roberts Noble Foundation and Texas A&M University in 1997.

Whitetails are of considerable economic importance due to their popularity as game animals. The increasing demand for trophy hunting and the advent of quality deer management has made white-tailed deer the most intensively researched and managed big game species in the U.S. However, despite an enormous amount of deer research, there are many aspects of deer ecology where knowledge is lacking. For example, conventional wisdom says that mature bucks with large antlers should be the most successful breeders, yet there is no hard evidence to support this hypothesis. Paternity testing, using microsatellite DNA, now makes determination of reproductive success and paternity in wild populations feasible.

The cooperative research team's first objective was to develop a panel of molecular markers for use in white-tailed deer. Because these markers often are conserved across species, biologists screened markers developed for use in domestic sheep and cattle, white-tailed deer, and mule deer to minimize development time and expense. The process resulted in a panel of 20 microsatellite loci optimized for use in white-tailed deer. The large number of loci makes this panel useful for application to parentage determination and population genetics studies. Wildlife biologists are interested in examining population structuring and reproductive success in free-ranging deer. Therefore, the marker panel on deer from populations in Florida, Oklahoma, Mississippi, and Texas was tested to determine the panel's resolution and the geographic range over which it is useful. Additionally, the panel to gauge the reliability of parentage determination using captive deer of known ancestry from the Mississippi State University captive animal facility was tested. The results demonstrated that the panel is highly useful for paternity exclusion and population genetic studies in white-tailed deer over a broad geographic range.

Wildlife biologist are now investigating male reproductive success in free-ranging Mississippi deer populations with the goal of finding out which bucks are doing most of the breeding. In addition, biologists are researching the effect of social dominance on a buck's reproductive success in the MSU captive facility. The bucks' behavior during the breeding season is being observed, and then paternity testing is conducted on fawns that are born the following summer. Preliminary results indicate that the dominant males do most of the breeding, although other subordinate bucks do manage to sire fawns. One interesting development of the captive research was that more than one buck can share paternity for a set of twins born to a single doe, which has never been documented in deer. Sampling in wild populations will allow biologists to document how many fawns are produced by bucks at various sex ratios.

Wildlife biologists are also comparing the genetic similarity of Mississippi deer populations. Deer populations throughout the Southeast were reduced to very low levels in the early 1900s due to unrestricted harvest and habitat loss. State and federal agencies restocked deer from other states and viable populations within Mississippi. It is believed that several populations in the Mississippi Delta and southwest Mississippi are native deer which recovered, while others were significantly affected by restocking programs. In addition, some currently accepted white-tailed deer subspecies designations may not be valid based on data.

The high-end equipment in the Noble Foundation's labs enable fast and efficient processing of large numbers of samples. The deer genotype database currently contains >1,400 animals and will be used to examine other questions of interest, such as correlating antler size with heterozygosity (e.g., genetic variation) and relating differences in breeding dates to genetic differentiation. This research is expected to have a tremendous, positive effect on white-tailed deer ecology and management.

This article can be accessed from the Mississippi State University Forest and Wildlife Research Center at the following URL:

http://www.cfr.msstate.edu/fwrc/wildlife/genetics.htm