Breeding behavior and secondary sex characteristics of male white-tailed deer in southern Texas

Environmental variation can influence forage quality and quantity which in turn can affect body condition. Body condition can affect many aspects of white-tailed deer biology, including reproduction and secondary sex characteristics. I studied male mating strategies, female reproductive success, and antler growth in southern Texas, a semi-arid environment with variable rainfall.;I captured 106 male white-tailed deer during 2006-2009, and fitted each male with a GPS radio-collar programmed to acquire locations during the rut (November to January). During peak rut, males increased movement rates, remained within home ranges except for brief excursions, and most did not conform to Levy movements. Relative to other rut phases, focal points were re-visited more often, but residency time was shortest. This behavior suggests that males may rely on spatial memory by returning to profitable areas to briefly assess female receptiveness. During drought years, such behavior was less prominent, as males were 67% more likely to remain in close proximity to a single focal point. This may be a strategy to reduce cost associated with poor body conditions during drought years.;I used 6 enclosures with supplemental nutrition and 6 without to determine influence on reproductive success. Young fed males (≤2.5 year old) sired 13% offspring while no unfed young males sired offspring. All adult females had high pregnancy rates however; mature females recruited most offspring in fed (76%) and unfed (83%) enclosures. Compared to unfed mature females, fed mature females raised more fawns (49% vs. 23%), raised more twins (31% vs. 9%), and had higher fetal counts (1.85 vs. 1.50). Supplemental nutrition allowed females to increase reproduction but did not substitute for maternal experience.;I captured 30 to 150 males annually at 7 southern Texas sites to determine repeatability of antler traits. Repeatability is the intra-class correlation between repeated measures of the same trait. Repeatability was moderate to high (0.42-0.82) for all traits. Repeatability of several traits from variable rainfall sites was lower than consistent rainfall sites. Sites with variable rainfall had 13-18% higher repeatability when feed was available. The association between repeatability and variable environmental conditions supports the role of antlers as an honest advertisement of individual condition and illustrates the magnitude of environmental influence on antler traits.;Collectively, my data improve the understanding of how the environment influences deer biology and ecology in semi-arid rangelands. The extent of environmental influences on deer was quantifiable as the availability of supplemental nutrition resulted in more consistent antler expressions and higher reproductive rates in both males and females. Lastly, the movement data improves our understanding how males search for females in an environment that can influence body condition.