Doctoral Candidate
Project Title:  Population Genetics, Breeding Success and Mating Strategies of White-tailed Deer.

Dissertation Project Abstracts

Temporal Distribution of Buck Breeding Success: How Do Young Bucks Compete?

Jason A. Sumners, Randy W. DeYoung, Rodney L. Honeycutt, David G. Hewitt, Mickey W. Hellickson, Kenneth L. Gee, Robert A. Gonzales, and Mitchell A. Lockwood

In age-structured populations, a small number of dominant bucks were long thought to do most or all of the breeding.  Surprisingly, recent studies are finding that more bucks are breeding than previously realized.  Although mature bucks (3.5 years and older) are most successful on average, young (1.5 and 2.5 year old) bucks collectively sire about 30% of fawns produced, even in populations containing a large proportion of mature bucks.  The finding that some young bucks are able to obtain matings raises some interesting questions about buck behavior.  For instance, what circumstances allow young bucks to sure fawns?  Young bucks could be successful at the end of the rut, when most mature bucks may be exhausted from breeding activities.  Alternatively, young bucks may be successful during peak rut, when many does are in estrous at the same time, providing more opportunities for all bucks.  Our long-term study of breeding success at the King Ranch is providing some insights to understand how young bucks can be successful breeders.  Using genetic parentage methods and tissue samples from does and embryos with known conception dates, we can determine if young bucks are successful during early, mid or late rut.  Our preliminary data indicate that young bucks are most likely to be successful breeders during peak rut.  Additional years of data collection will provide a clearer picture of buck breeding behavior.
Cooperative funding and in-kind support provided by King Ranch, Inc., Texas Parks and Wildlife Department, Samuel Roberts Noble Foundation, and the Quality Deer Management Association

Breeding Behaviors of Male and Female White-tailed Deer Relative to Age Class 
Jason A. Sumners, Randy W. DeYoung, Rodney L. Honeycutt, Stephen Demarais, Mickey W. Hellickson, Kenneth L. Gee, and Robert A. Gonzales 

 Although the breeding system of white-tailed deer is commonly described as a dominance-based hierarchy, recent studies have documented the breeding success of all age classes of bucks in white-tailed deer.  It has been suggested that the breeding success of young bucks is the result of exclusively mating with young does, while older bucks concentrate their efforts on mature does, presumably because these does are more experienced and more likely to recruit 1 or more fawns. Additionally, older does may not tolerate mating attempts of younger bucks, preferring to mate with dominant bucks..  The occurrence of multiple paternity in many white-tailed deer populations indicates that female choice may play an important role in determining the distribution of buck breeding success.  We are sampling litters of fawns and assigning paternity using a panel of genetic markers.  Our preliminary results indicate that yearling bucks successfully mate with does of all ages.  The mean age of female mates was 5.1, 4.8, 5.0 for 1.5, 2.5, and 3.5+ year-old bucks, respectively.  Additionally, we documented two incidents of multiple paternity involving yearling bucks.   The breeding success of young bucks may be restricted to the peak of the breeding season when the most does are in estrous and mature bucks cannot monopolize access to all does.  The lack of an association between buck age and doe age is more evidence that over all male-male competition may not play an important role in gaining access to does.  Our ongoing work should provide further insights into breeding behavior and success of while-tailed deer.
Cooperative funding and in-kind support provided by King Ranch, Inc., Texas Parks and Wildlife Department, Samuel Roberts Noble Foundation, and the Quality Deer Management Association