White-tailed deer (Odocoileus virginianus) fawn survival is an important component of population dynamics. My study was replicated on 2 ranches in South Texas with 2 low-density (0.12 deer/ha) non-supplemented enclosures, 2 high-density (0.49 deer/ha) non-supplemented enclosures, and 2 high-density (0.49 deer/ha) supplemented enclosures. Each enclosure was 81 ha in size. Fawns were captured with the aid of vaginal implant transmitters expelled when does gave birth, fitted with expandable mortality collars, and monitored daily. During summer 2011 and 2012, 18 and 27 fawns were captured, respectively. The known fates model in program MARK v. 7.1 was used to model survival of fawns to 35 weeks of age during summer 2011-spring 2012 (drought) and summer 2012-spring 2013 (average rainfall). Bed-site characteristics were analyzed at birth, 7, and 14 days of age. Canopy cover, distance to nearest shrub, concealing cover, and temperature of birth and bed sites were compared with a random site. Fawn survival was affected by rainfall and supplemental feed. Survival was <10% at 35 weeks of age during both years for fawns with no supplement compared to 40% in 2011 and 60% in 2012 for fawns provided supplemental feed. Survival also increased with fawn body length at birth such that small fawns had <5% survival to 35 weeks even in the presence of supplement. Large fawns had 40 and 90% survival in non-supplemented and supplemented enclosures, respectively. Fawn bed-sites had >15% higher percent shrub cover than random sites (P<0.05). Fawns also selected sites >10% higher in litter (P<0.01) and >20% lower in bare ground (P<0.01) when compared to random sites. The distance to the nearest shrub to the East and West was >1 m less for fawn sites than random sites (P<0.05). Concealing cover in each cardinal direction was >20% higher than random sites (P<0.01). Fawns chose sites that were >2°C cooler than random sites (P=0.06). My data suggests survival will increase in higher rainfall years with supplemental feed. Rainfall also allows for proper vegetation structure for bed-sites. This could increase survival by allowing fawns to evade predators and/or the heat of South Texas by selecting for highly concealed sites with high shrub cover.
August 28, 2015
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