White-tailed Deer Buck Movements During the Rut

 By David G. Hewitt, B&C Club Professional Member

The rut can be a particularly exciting time to be afield. Bucks and bulls have one thing on their mind. The intense focus on breeding dramatically changes their behavior. Bachelor groups break up, feeding becomes a distraction, and being secretive and discrete is no longer an advantage. Bucks and bulls come out of cover and into the open to chase, court, and guard females. Wild spaces ring with bugles, grunts, and rattling antlers.

To gain greater insight into the world of a rutting male, scientists at the Caesar Kleberg Wildlife Research Institute have been fitting white-tailed deer bucks with collars that contain a GPS unit. These GPS collars record the buck’s location every 20 minutes from the beginning of November through the end of February. This period encompasses the peak of the rut, which is mid to late December in the South Texas study area.

Over the past three years, collars have been placed on over 60 bucks. By analyzing the thousands of locations obtained for each buck, a picture of buck movements before, during, and after the rut becomes clear. To date, we have analyzed data from 33 bucks and the home range of these deer during the 4-month monitoring period averaged 2,967 acres. Although home ranges of over 4.5 square miles seemed large, what was a greater surprise was the huge variation among individual bucks.  The smallest home range was 332 acres and the largest was 13,648 acres! There was a general decrease in home range size as deer aged from yearlings to 3 years of age and then an increase in mature bucks. 

Daily movements in November averaged just less than 3 miles per day. That movement rate jumped to over 5 miles/day during December and over 6 miles per day at the peak of the rut. Again, there was a great deal of variation amongst individual bucks. For example, during December daily movement ranged among bucks from 2.5 miles to over 8 miles per day.

Excursions, defined as short term (usually less than 24 hours) trips that occurred outside of the home range, peaked in December. In fact, every one of the 33 bucks we have analyzed so far has made at least one excursion in December. Fewer than half the bucks made excursions in other months. Some excursions during the rut covered extraordinary distances. For instance, one buck made an 18-mile, round-trip excursion in early December, then 10 days later made another excursion that covered 11 miles.

So what? There are several lessons that this gee-wiz GPS technology can impart:

• The great increase in movements during the rut explains why hunters are often successful hunting trophy bucks during the breeding season. It also explains why bucks that have not been seen before suddenly show up during the rut, and why they can just as quickly disappear.

• The high rate of daily movement, coupled with bucks focusing on breeding instead of eating, explains why they lose up to 30% of their body weight in a 4-6 week period. The stress of the rut helps explain why 80% of non-hunting mortality in bucks occurs from December to March in southern Texas.

• The large movements of bucks during the rut make it imperative that white-tailed deer are managed at a large scale. One property, even if it is small, can harvest so many bucks that few reach maturity, denying nearly everyone in the region a shot at a trophy buck. 

Consequences of maternal effects on body and antler size of white-tailed deer

By Kevin L. Monteith (B&C Official Measurer), Jonathan A. Jenks (Distinguished Professor, South Dakota State University), R. Terry Bowyer (B&C Professional Member)

Although only one subspecies of white-tailed deer (O. v. dacotensis) inhabits South Dakota, deer occupying the Black Hills of southwestern South Dakota are smaller than those in the eastern portion of the state. Average body weight of adult females from eastern South Dakota is 25% heavier than females from the Black Hills. The Black Hills region is characterized by coniferous forests with little understory forage, whereas eastern South Dakota is dominated by high-quality agricultural crops. Disparity in size of deer between these two areas is probably related to differences in forage quality. What would be the effect of improving nutrition of deer from the Black Hills? Would they increase in size and how long would it take for a change in nutrition to have a positive effect on growth?

To answer these questions, we captured newborn fawns from both regions and hand raised the animals using comparable husbandry practices. This approach ensured there were no environmental differences influencing diet, growth, and variability in investment by nursing mothers. Animals were bred in captivity to obtain offspring from 1st-generation Black Hills and eastern South Dakota deer. We raised 2nd-generation animals under conditions identical to those for 1st-generation animals. Males were weighed frequently throughout the study and annual growth of antlers was measured with the Boone and Crockett scoring system for ages up to 7 years.

Despite being in good nutritional condition, adult males that originated from the Black Hills ceased rapid body growth 41 days earlier, were 29% smaller in body weight (170 lbs), and grew smaller antlers (104 inches) than bucks from eastern South Dakota. Male offspring of 1st-generation deer from the Black Hills attained a 30% larger body weight at maturity and grew larger antlers than their fathers. Body weight (222 lbs) and antler size (136 inches) of those 2nd-generation males of Black Hills origin approached that of 1st-generation males (240 lbs; 152 inches) from eastern South Dakota at maturity. In contrast, 1st and 2nd-generation males of eastern South Dakota origin differed little in body or antler size.

Identifying maternal effects on offspring is critical to interpreting population dynamics of ungulates, but the duration and influence of maternal effects on offspring are not well understood. Poor forage can negatively affect growth of male ungulates, and providing a high-quality diet is expected to improve growth. Contrary to that prediction, male white-tailed deer fawns from the Black Hills raised in a controlled environment on a high nutritional plane, remained smaller in both body weight and antler size compared with males acquired from eastern South Dakota. Nevertheless, offspring of those Black Hills males attained a markedly larger body and antler size than their fathers, which supported an influence of maternal and grandmaternal condition during gestation on subsequent growth of offspring. That pattern of growth is known as a negative maternal effect, which was likely caused by poor forage conditions in the Black Hills. Moreover, these outcomes do not support a strong genetic component because deer of Black Hills origin recovered in body and antler size in the 2nd generation.

Implications for research and management of ungulates:

• Increases in forage quality, whether brought about by a reduction in the deer population or improvement of habitat, may not immediately result in increased body and antler size of males—management agencies and hunters need to be patient.

• Maternal effects may be more pronounced than previously recognized and can complicate interpretation of population dynamics, especially about predictions of body and antler size with improved nutrition.

• Fawns born small to mothers in poor physical condition will likely never recover and remain smaller in both body and antler size to those fawns born under improved conditions.

• Maternal effects also may be confused with individual quality of deer. Individual quality requires a strong genetic component that we did not identify. Our results indicate that nutrition rather than genetics has a stronger influence on growth of antlers.

Funding for this research (Monteith, K. L., L. E. Schmitz, J. A. Jenks, J. A. Delger, and R. T. Bowyer. 2009. Growth of male white-tailed deer: consequences of maternal effects. Journal of Mammalogy 90:651-660) was provided by Federal Aid in Wildlife Restoration administered through the South Dakota Department of Game, Fish and Parks, South Dakota Agricultural Experiment Station, National Science Foundation/EPSCoR Grant, and a Griffith Faculty Research Award presented to J. A. Jenks. Readers can request a copy of the original paper from This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Conservation and Management of Mule and Black-tailed Deer

By Emily Latch – Purdue University and now at University of Wisconsin-Milwaukee 

Gene Rhodes – Purdue University

Jim Heffelfinger – Arizona Game and Fish Department and Boone and Crockett Professional Member

Throughout the geographic range of mule deer and their black-tailed subspecies (Odocoileus hemionus), we see a lot of variation in body size, coat color, antler shape, behavior, and other attributes. For instance, mule deer in the southern latitudes are generally smaller than those in the north and those inhabiting the deserts appear lighter in color than those in heavily forested regions. The large degree of physical variation observed in mule deer led early naturalists to collect mule deer from a few geographically distant locations and designate them as different subspecies because they differed slightly from one another.

Recent advances in DNA analysis techniques now allow researchers to evaluate genetic data in ways that provide managers with meaningful ecological management units on an ecoregion scale throughout the range of a species. To gain insight into the genetic basis of differentiation in mule deer, we teamed up with a coalition of conservation groups to undertake one of the most ambitious projects of its kind, to study the genetic characteristics of nearly 2,000 mule and black-tailed deer from across their range.  

We have recently published the first set of analyses, detailing variation in mitochondrial DNA in mule and black-tailed deer. The mitochondrial DNA dataset is the most appropriate for evaluating the accuracy of the existing subspecies and to define large geographic units of similar deer. Future analyses will investigate nuclear DNA which will provide a much higher-resolution look at genetic diversity throughout North America and an even better tool to address conservation and management questions. Our first set of analyses have revealed some exciting results:

Genetic variation is very high in mule deer – we identified 496 different types of mitochondrial DNA in the1,766 mule deer included in the full analysis.

Mule deer and black-tailed deer are genetically distinct – in agreement with previous studies, we found that the two types differ by as much as 7.7%.  This is on par with differences between many closely-related species of North American mammals.  

Black-tailed deer likely survived through the last glaciation in a refugium along the west coast of Washington and Oregon.  As a result, black-tailed deer have reduced genetic diversity compared to mule deer.

Mule deer probably existed in many southern refugia at very high population sizes, because much of the genetic diversity in mule deer has been retained.

Patterns of genetic structure across North America loosely correspond to currently recognized subspecies; however, we found three interesting deviations from this pattern: 1) the previously described ‘Inyo mule deer’ were not distinct from other mule deer in California; 2) Sitka black-tailed deer is not strongly differentiated from Columbian black-tailed deer, which suggests that the Sitka may be a coastal form of blacktail influenced by its environment; 3) some desert mule deer collected in the Texas panhandle, West Texas, and southeastern New Mexico show a strong genetic difference from surrounding areas despite the fact that they are currently not geographically isolated from other desert mule deer.

Support for this large scale project came from a coalition of conservation partners, including the Boone and Crockett Club, Pope and Young Club, National Fish and Wildlife Foundation, Camp Fire Conservation Fund, Safari Club International (SCI), Purdue University, Arizona Game and Fish Department, Dallas Safari Club, Seattle Chapter of SCI, University of Arizona, and California Deer Association.

The article from which information was drawn for this edition of Trophy Points is:  Latch EK, Heffelfinger JR, Fike JA, Rhodes OE.  2009.  Species-wide phylogeography of North American mule deer (Odocoileus hemionus): cryptic glacial refugia and postglacial recolonization.  Molecular Ecology 18:1730-1745.

Fact Stranger Than Fiction: Bears Afraid of Deer?

In most instances, a confrontation between a white-tailed deer and a black bear would be decided in favor of the bear. Dr. Steve Côté, a scientist with the Université Laval in Quebec, has indentified a situation which defies this conventional wisdom. Dr. Côté and his colleagues have been studying white-tailed deer on Anticosti Island, a 3,000-mile island in the Gulf of St. Lawrence in Quebec. Until the late 1800s black bears and mice were the only herbivorous mammals on the island. Bears were abundant in large part because of large, diverse berry crops. In 1896, 200 white-tailed deer were released on Anticosti Island and in 30 years their numbers had increased to over 50,000.

For some period after the introduction, bears probably benefitted from the white-tailed deer, learning to catch fawns in the spring and feeding on deer carcasses when they were available. However, as the years passed, bears begin to have difficulty finding enough food in autumn to acquire the fat stores necessary to hibernate through the long cold winters. Bears are particularly sensitive to a decline in autumn food because pregnant females give birth in February while in their dens. Sows nurse their cubs for up to 3 months before emerging. Thus, for bears to reproduce, females must not only acquire sufficient reserves to ensure their own survival over winter, but they must store enough fat to support the growth of their cubs.

Deer relish berries, and they also like the bushes that produce berries. For this reason berry bushes, not to mention berries, are rare on Anticosti Island now. Black bears are no longer found on the island, despite their populations doing remarkably well in nearly all other portions of their range. All indications are that overabundant deer, perhaps topping 100,000 in recent decades, extirpated black bears from the island.

What does this mean to those interested in wildlife management and conservation?

• A simple action, like releasing 200 deer onto an island, can have far reaching implications.
• Failure to manage the abundance of one species can decimate others.
• Conventional wisdom cannot always predict outcomes in the natural world. In some circumstances, bears should live in fear of deer.

For more information see Extirpation of a Large Black Bear Population by Introduced White-tailed Deer by Steve Côté, Conservation Biology 19:1668-1671.