TEXAS WILDLIFE
CAESAR KLEBERG WILDLIFE RESEARCH INSTITUTE TEXAS A&M UNIVERSITY-KINGSVILLE
Recruitment of White-tailed Deer Fawns in Texas Investing in Future Herds
Article and photo by MICHAEL J. CHERRY, Stuart W. Stedman Chair for White-tailed Deer Research
Doe on the East Foundation’s San Antonio Viejo ranch during late gestation in 2020.
P
opulation dynamics of white-tailed deer are often characterized by stable adult survival rates, and variable fawn recruitment. Fawn recruitment can be influenced by many factors and is often much more sensitive than adult survival to environmental variability. There are circumstances such as extreme drought, where all deer, independent of nutritional condition experience suppressed reproduction or fawn survival. However, such events are rare and generally deer in better nutritional condition have higher probability of survival and a reproductive potential that is more resilient to environmental variation.
The intuitive mechanism connecting nutritional condition to fawn recruitment is that fawns in poor condition are more susceptible to disease, starvation and exposure. However, there are likely more subtle linkages as well. For example, deer in poor condition may be more susceptible to predation because they engage in more risky behaviors to meet their energy requirements. While there is abundant evidence that nutrition can influence population dynamics of deer, there is also emerging evidence that conditions experienced during early life may be important in determining the lifetime growth potential for deer. Luxury traits, or characteristics that do not affect survival but enhance reproductive potential such as antler size, may be especially sensitive to early life conditions. It appears offspring resource allocation between efficiency traits, which enhance survival, and luxury traits may be a result of maternal effects. Maternal effects are the programming mothers provide to offspring to prepare them for local environmental conditions. Maternal effects are thought to be driven by epigenetic mechanisms. Epigenetic change is the heritable change in gene expression that is independent of changes in DNA. The heritable nature of material effects explains why it took multiple generations to overcome regional effects on body and antler sizes in captive experiments where deer were all provided equivalent high-quality diets. Therefore, a bad year may not only reduce the number of fawns recruited, but the quality of surviving individuals in terms of body and antler size for their entire life. If the gene expression is also heritable these effects will also be seen in their offspring's characteristics. In wildlife, this phenomenon is referred to as a cohort effect, and in deer this effect has been shown to transcend generations, as fawns pass along epigenetic changes in the way offspring express genes. Ultimately, if managers seek to improve
Sponsored by JOHN AND LAURIE SAUNDERS
20 T E X A S W I L D L I F E
JUNE 2021
