A generalized nutrition model for Odocoileus deer and its application in a natural environment

Abstract

A model of protein and energy balance was created for Odocoileus deer [white-tailed deer (Odocoileus virginianus), mule deer (O. hemionus), and black-tailed deer (O. h. columbianus, O. h. sitkensis)] capable of predicting changes in body weight and fatness. Our model is not restricted for use by sex, age, season, climate, or eco-region. The model also measures animals' ability to produce offspring, milk, and antlers. I created this model through integration of all previous reductionist studies regarding physiology and nutrition of Odocoileus deer and related species. The model was designed to be highly useable, accessible and useful to resource managers, wildlife agency policy makers, and wildlife researchers. Minimal inputs for operation include: harvest weights by sex and age class, timing of peak rutting period, average fetuses/doe, estimated energy and protein content of diet, and environmental conditions (minimum/maximum temperature, windspeed, humidity, and snow depth). Age, energy content of diet, physiologic stage, and changes in photoperiod affect intake. Energy requirements are the sum of: basal metabolism, active energy expenditures, thermoregulation, gestation, lactation, and obligate growth. Basal endogenous nitrogen, gestation, lactation, antler development, and obligate growth determine protein requirements. The most limiting of the two nutrients determines changes in mass. The model was validated using 3 previously published studies (Fowler et al. 1967, Short et al. 1969, Wheaton and Brown 1983) of intake and mass change deer fed ad libitum, for 2 or more years. I also validated the model by using it to predict average live harvest weights by age & sex class of white-tailed deer collected during the 2000-2001 hunting season at the Kerr Wildlife Management Area (WMA). The model closely predicted observed changes in body mass in the published studies but significantly over-estimated intake. The model performed very well under field conditions at the Kerr WMA by correctly predicting harvest weight for all modeled age and sex classes to within 3 kg, except for yearling males. Overall, I feel that the model performed well and that the structure and formulation of this model can serve as a basis from which other generally-applicable nutrition models can be formed for ruminant wildlife species.