Grazing pressure impacts on potential foraging competition between Angora goats and white-tailed deer

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Abstract Increased Angora and Spanish goat populations in the Tamaulipan Province of southern Texas and northeast Mexico and the economic importance of white-tailed deer lease hunting in the region has heightened concern as to negative interactions between these two herbivores. This study selected a shallow ridge range site, dominated by palatable shrubs, as a high potential community for herbivore interaction at the landscape level. The site was stocked at 0, 2, 4, 6 goats/ha on an experimental ranch in South Texas. Deer and goat biting tactics, diet selection and reconstructed dietary crude protein and digestible organic matter were compared across stocking treatments. Dietary overlap indices were 0.75-0.88 between the herbivores across season and stocking rate. Deer had a greater tendency to use nip bites than goats in the non-grazed pastures (60–65% vs. 42–55%, respectively). However, goats increased the use of nip bites more than deer as intraspecific competition increased while deer used similar strategies across all stocking rates. Increased stocking rates had little impact on dietary composition of woody species in the diet of goats. The greatest dichotomies of dietary selection between both herbivores was shrubby bluesage where deer exhibited a positive preference while goats generally avoided the species, regardless of its availability. Both herbivores were generally able to stabilize nutrient concentration in their respective diets regardless of grazing pressure by goats.