In the January 2011 Ag News and Views, Ken Gee discussed ground shrinkage - the phenomenon of a harvested buck looking smaller than he appeared in life - and how to avoid it. If you are willing to pass up a few bucks next year, you may begin to wonder what will happen to them during post-rut (January, February and March.) In fact, "What happened to all of the bucks I saw last year?" is a common question.
Most biologists believe that nutritional stress during fall (October - December) and following rut can cause bucks to become weakened and more susceptible to natural mortality. During rut, bucks often ignore eating in favor of locating does that are ready to breed. After the rut, forage quality and quantity may be lacking, making it difficult for bucks to recover from rut-associated stresses sufficiently to avoid predation or overcome disease. Post-rut mortality is a major contributor to the inefficiency of trophy buck management. However, those who understand trophy or quality buck management also understand a buck's antlers will not grow larger if he's killed at a young age by a hunter.
Based on one South Texas study, only 24 out of 100 bucks can be expected to reach the age of 6 due to natural mortality1, with 77 percent of bucks dying post-rut. One might think that it would be logical to control predators to increase post-rut survival. However, a study in the same area showed that coyote control had no significant effect on the number of bucks or the age structure of bucks, and that buck survival could not justify the expense of coyote control. A more recent South Texas study found that 52 percent of radio-collared bucks survived to 6 years old. This study was conducted on a ranch that provided limited supplemental feed and, probably most significantly, received above average rainfall during the last two years of the study.
These are South Texas studies, but they raise questions about the significance of post-rut mortality in southern Oklahoma and northern Texas, and how it might be avoided. Differences in climate and habitat quality are likely variables, but there are really only two practical management techniques to increase buck survival and age structure that are required for successful trophy or quality buck management.
Of greatest importance is improving deer habitat quality over as large an area as possible. Deer habitat should consist primarily of native plants, including grasses, forbs, shrubs and trees. Quality is managed through properly timed disturbances such as grazing and fire, or properly timed lack of disturbance (rest). The intensity and/or length of time these tools are or are not applied also influence habitat quality. The desired outcome is a landscape containing a diversity of plants in differing stages of growth, resulting in areas with varying mature plant growth mixed with areas of fresh plant growth. A landscape such as this provides natural foods for bucks during the winter. These foods consist of, but are not limited to, cool-season legumes and grasses. Woody plant diversity improves mast availability and browse quality. Providing a diversity of plants and plant structure throughout the landscape will allow deer to obtain a high quality diet within a small area.
Plant diversity and structure also provide screening cover to help deer avoid predation and thermal cover to help them maintain body heat during extremely cold weather. Providing supplemental feed is an option, but it's expensive and, therefore, it's usually not offered in sufficient quantities to supplement all of the bucks in a given area. Food plots fall into the same category as supplemental feed, but food plots also require rainfall. Even in the driest of winters, naturally occurring plant communities will always provide some food for deer, while food plots will not.
In addition to habitat management, consider establishing conservative buck harvest limits. This does not help a buck survive post-rut stresses, but it can increase the number of surviving bucks by reducing hunting mortality.
Providing quality habitat consisting of primarily native plants over as much land area as possible is the most fundamental and practical way to increase post-rut survival and help avoid ground shrinkage problems.
1 The study did not include hunting mortality.