| Optimum management of white-tailed deer herds is important to many stake-holders in south Texas. My objectives were to analyze white-tailed deer population dynamics as influenced by deer density and nutrition, model the population dynamics on simulated 20.2 km2 pastures in order to analyze the effects on trophy buck (Boone and Crockett score > 160) production, and compare population estimate techniques. Three target densities were analyzed with enhanced nutrition provided to half the populations. Enhanced nutrition had a positive effect (P ≤ 0.05) on all demographics analyzed except yearling antler growth. Density dependence was displayed in the indigenous nutrition enclosures as mature deer body mass decreased with increase in density from medium to high (F2,5 = 3,88, P = 0.01). Population growth rate (lambda), Fawn:doe ratios, fawn and yearling growth rate, fawn survival, and adult survival did not display density dependence. Trends in population growth rate (lambda) indicated a weak density-dependent relationship and both enhanced and indigenous nutrition populations displayed a constant growth rate over the range of densities analyzed with a 30% higher lambda population growth rate in the enhanced nutrition treatments. When modeling the population dynamics in the enhanced nutrition pastures, there was a direct relationship between density and number of trophy bucks produced. In the indigenous nutrition pastures, the medium density produced the most trophy bucks. For estimation of bucks, all methods analyzed were accurate within 1 buck. When estimating female deer, timing of survey had no affect on accuracy (F3,216 = 0.07, P = 0.55), whereas estimates of fawns was more accurate in January than in September when using the modified Jacobson technique (F1,108 = 61.2, P < 0.001). In south Texas's highly variable nutritive environment, monitoring for a decrease in mature deer body mass was the first indicator of density-dependence available to managers. Nutrition is clearly limiting in the south Texas landscape, as improving the nutritive state with enhanced nutrition resulted in improved performance in individual deer and their population dynamics. |
