Comparison of techniques for determining the nutritional carrying capacity for white-tailed deer

Abstract

Estimates of carrying capacity for herbivores are useful for determining the relative value of different ranges. We compared 6 estimates of nutritional carrying capacity for white-tailed deer (Odocoileus virginianus L.): digestible energy consumed by tame deer, and 5 methods using forage supplies of dry matter, digestible energy, digestible nitrogen, dry matter*digestible energy, and dry matter*digestible nitrogen in two 1-ha enclosures of different shrub plant communities in southern Texas. For the north enclosure, carrying capacity estimates (90% CI) were 3.65 (CI = 3.61-3.69), 4.5 (CI = 3.7-5.3), 9.4 (Cl = 73-11.5), 15.2 (CI = 11.6-18.8), 3.5 (CI = 2.7-4.3), and 3.5 (CI = 2.7-4.3) deer ha-1 58 days-1 for the digestible energy tame deer, dry matter, digestible energy, digestible nitrogen, dry matter*digestible energy, and dry matter*digestible nitrogen techniques, respectively. Corresponding estimates for the south enclosure were 2.6 (CI = 2.5-2.7), 3.5 (CI = 3.2-3.9), 6.8 (CI = 6.0-7.6), 10.1 (CI = 8.8-11.3), 2.1 (CI = 1.8-2.6), and 2.8 (CI = 2.4-3.1). Some methods for estimating carrying capacity provided different absolute estimates, but all produced similar relative estimates between enclosures. Similar relative results between enclosures suggests any of the methods can be used to determine the relative nutritional quality of plant communities. However, the dry matter-based technique was less expensive than the other techniques; therefore, there is no need to use more costly techniques for determining the relative stocking rates for white-tailed deer, unless forage quality differs greatly among plant communities.