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Carrizo Springs, TX, United States

Donohue R.N.,Texas A&M University-Kingsville | Donohue R.N.,U.S. Fish and Wildlife Service | Hewitt D.G.,Texas A&M University-Kingsville | Fulbright T.E.,Texas A&M University-Kingsville | And 3 more authors.
Journal of Wildlife Management | Year: 2013

Concentrated food sources are used frequently in white-tailed deer (Odocoileus virginianus) management and research, but because such food sources are easily defended, aggressive interactions among deer may influence their effectiveness. The objectives of this study were to determine if deer population density or season affect 1) the order or degree of social dominance among different age and sex groups of white-tailed deer, 2) the rate at which aggressive interactions occur, 3) the severity of interactions, and 4) the extent to which subordinate groups avoid dominant groups. We conducted our study in South Texas using 2 sets of 3, 81-ha enclosures managed at varying deer population densities. We captured aggressive interactions using digital trail-cameras placed at sites with spatially concentrated food. We found that bucks ≥2 years of age were dominant over all other age and sex groups in ≥87% of their interactions regardless of deer density or season. The odds of a buck dominating over a doe increased by 10% (95% CI = 0-21%) for each additional deer/km2 during summer, but density had little effect in any other season. Yearling bucks were dominant in 81% (95% CI = 51-100%) of their interactions with does during spring, whereas during other seasons we found no clear order to the dominance hierarchy. Social dominance between yearling bucks and does was not affected by population density. The rate of aggressive interactions increased by 2% (95% CI = 1-3%) for each additional deer/km2 and did not differ by season. Ten percent (95% CI = 6-14%) of interactions involved more violent behaviors that we characterized as severe; this percentage did not change with population density or season. At all population densities, during all seasons, does avoided bucks at sites with concentrated food; however, the degree of avoidance declined with increasing deer density in all seasons except spring. Our results indicate that as population density increases, so do social pressures that may limit access of subordinate age and sex groups to concentrated food sites. Therefore, concentrated food sites are not equally accessible to all age and sex groups of deer and the effectiveness of such sites in deer management and research may become increasingly limited as population density increases. © 2013 The Wildlife Society. Copyright © The Wildlife Society, 2013. Source

Crider B.L.,Texas A&M University-Kingsville | Crider B.L.,South Dakota State University | Fulbright T.E.,Texas A&M University-Kingsville | Hewitt D.G.,Texas A&M University-Kingsville | And 6 more authors.
Journal of Wildlife Management | Year: 2015

Diet selection theory predicts that selective foraging by white-tailed deer (Odocoileus virginianus) may reduce palatable and nutritious plants when high-quality food resources are available or deer densities are high. Our objectives were to determine if providing a high-quality food resource ad libitum and increasing deer densities 1) reduced standing crop and nutritional quality of forbs and 2) altered standing crop and nutritional quality of grasses and shrubs. We used 6 81-ha controlled-density enclosures on each of 2 study sites in southern Texas with deer densities considered low (12 deer/km2), medium (31 deer/km2), and high (50 deer/km2) relative to the range of population estimates for white-tailed deer in the Rio Grande Plains of Texas. For each pair of enclosures with the same deer density at each study site, we provided white-tailed deer in 1 enclosure high-quality pelletized feed ad libitum and did not provide feed (control) in the other enclosure. During spring and summer 2004-2012, we estimated standing crop of forage in 40 0.25-m2 × 1.5-m volumetric plots/enclosure and we harvested 20 randomly selected plots/enclosure, which we dried to convert wet mass estimates to dry mass. Availability of high-quality pelletized food and deer density did not affect (P≥0.392) forb standing crop during spring and summer. Forb, browse, and grass standing crop and nutritional quality varied (P<0.001) with precipitation among years. Enclosures with low deer densities had lower forb crude protein than those with higher densities (P<0.034) during summer in drought years (2006, 2009, and 2011). Enclosures with high-quality pelletized food tended to have lower browse crude protein than controls (sampling date x feeding treatment interaction, P=0.051) in spring during 2006 and 2007. Variable and limited rainfall had a more pronounced effect on variation in vegetation standing crop than white-tailed deer foraging regardless of food resource availability or deer density. Vegetation responses were more complex than can be predicted by traditional theory on diet selection in part because of the pronounced effect of variation in rainfall on vegetation standing crop. © 2015 The Wildlife Society. Source

Foley A.M.,Texas A&M University-Kingsville | Deyoung R.W.,Texas A&M University-Kingsville | Lukefahr S.D.,Texas A&M University-Kingsville | Lewis J.S.,Texas A&M University-Kingsville | And 4 more authors.
Journal of Mammalogy | Year: 2012

Antler traits are both genetically determined and environmentally influenced. However, the degree to which environmental factors affect antler expression has rarely been quantified. We captured 30 to 150 male white-tailed deer (Odocoileus virginianus) annually at 7 South Texas sites during 1985 to 2009 to determine repeatability of antler traits from a semiarid environment with variable rainfall. Repeatability is defined as the intraclass correlation between repeated measures of the same trait over time. Repeatability was moderate to high (0.420.82) for all antler traits. Overall, number of antler points had the lowest repeatability, whereas inside spread of main beams and length of main beams had the highest repeatability. Repeatability of total antler score and number of antler points from sites with variable rainfall was 16 and 24 lower than sites with consistent rainfall, respectively. Sites with variable rainfall had 1318 higher repeatability when enhanced nutrition was available. Studies of cervids reveal a tendency for lower repeatability of antler traits as the environmental conditions become more variable. The association between repeatability and variable environmental conditions illustrates the magnitude of environmental effects and supports the role of antlers as an honest advertisement of individual condition or quality. Our results help to understand potential of microevolution in antlers and have implications for sexual selection and harvest management. © 2012 American Society of Mammalogists. Source

Bullock S.L.,Texas A&M University-Kingsville | Hewitt D.G.,Texas A&M University-Kingsville | Stanko R.L.,Texas A&M University-Kingsville | Dowd M.K.,U.S. Department of Agriculture | And 2 more authors.
Small Ruminant Research | Year: 2010

Whole cottonseed (WCS) is a potential supplemental feed for white-tailed deer (Odocoileus virginianus) in rangeland conditions because of its high digestible energy and protein content, moderate fiber content, and resistance to degradation in moist conditions. WCS also contains the polyphenolic secondary metabolite gossypol, which reduces palatability to non-target monogastric species but may be of concern for deer nutrition. Plasma gossypol stabilization when fed a constant dry matter intake, plasma gossypol depletion after WCS was removed from the diet, and the relationship between WCS consumption and plasma gossypol concentration was studied in 10 mature male (N= 5) and female (N= 5) captive white-tailed deer. Consumption of WCS by 73 free-ranging white-tailed deer (59 males, 14 females) was estimated using results of the captive study. Plasma gossypol concentrations declined exponentially and averaged 0.74 μg/mL 35 days after WCS was removed from the diet. Plasma gossypol concentration was linearly related to WCS consumption (P< 0.001), with females having 0.35 μg/mL greater (P= 0.04) plasma gossypol than males for a given rate of dry matter consumption. All female and 93% of male white-tailed deer captured in WCS supplemented pastures had detectable plasma gossypol. Female averaged 1.88 μg/mL of plasma gossypol and males averaged 4.84 μg/mL of plasma gossypol. Based on the captive deer data, these plasma values suggest an average WCS consumption of ∼2.6. g/kg BW/day for female free-ranging deer and ∼5.6. g/kg BW/day for male free-ranging deer. Inferentially, a large proportion of free-ranging white-tailed deer in rangeland conditions will consume WCS, with females consuming 125. g WCS/day and males consuming 428. g WCS/day. That plasma gossypol levels decrease rapidly after cottonseed is removed from the diet suggests that the long withdrawal periods often used prior to breeding season may not be needed. However, although 93% of gossypol was eliminated from the animals after a five-week withdrawal period, a small amount of gossypol can still be detected. While our preliminary data on these animals suggests that these levels are not detriment to animal health or reproduction, ranch managers may want to take a conservative approach to the feeding of WCS until these questions are answered. © 2010 Elsevier B.V. Source

Timmons G.R.,Texas A&M University-Kingsville | Hewitt D.G.,Texas A&M University-Kingsville | Deyoung C.A.,Texas A&M University-Kingsville | Fulbright T.E.,Texas A&M University-Kingsville | Draeger D.A.,Comanche Ranch
Journal of Wildlife Management | Year: 2010

Provision of supplemental feed to large herbivores is a common management practice that may motivate selective foraging, thereby influencing plant community composition. Our objective was to assess the effect of a high-quality supplement on diet composition and nutritional quality for white-tailed deer (Odocoileus virginianus). We permanently released hand-reared deer into 4 81-ha enclosures; in 2 enclosures we provided a pelleted supplement. We conducted bite-count studies seasonally to assess diet composition and quality. Supplemented deer reduced mast (fruits and pods of woody plants and cacti) in their diets (P < 0.019) during spring and autumn compared to unsupplemented deer. Diets of deer in supplemented enclosures had 2 times greater proportion of browse during spring (P= 0.065) and 5 times greater proportion of forbs during autumn (P= 0.007). Quality of the forage portion of the diet did not vary by treatment during winter or summer. Metabolizable energy concentration was 13 greater (P= 0.054) in spring and digestible protein content was 3 times greater (P= 0.006) during autumn in diets of supplemented compared to unsupplemented deer. Our results support the selective foraging hypothesis during autumn but not during winter, spring, or summer. Furthermore, white-tailed deer did not reduce the proportion of their diet composed of browse, but did reduce consumption of mast. Supplemented deer continued to eat poor-quality, chemically defended forage, perhaps to alleviate ruminal acidosis induced by the supplement or because nutrients in the supplement increased the deer's ability to detoxify chemically defended browses. A decline in mast consumption by supplemented deer could influence plant communities, depending on the role of deer in seed dispersal and seed predation. Impacts of supplemental feed on selective foraging of white-tailed deer in shrub-dominated rangelands are more complex than suggested by previous research. Long-term studies of vegetation communities are needed before wildlife managers will be able to fully incorporate effects of supplemental feed into management decisions. © 2010 The Wildlife Society. Source

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