Comparative foraging ecology of white-tailed deer and Angora goats on the Edwards Plateau, Texas

Abstract

This study investigated how seasonal patterns in forage abundance and quality influenced the feeding behavior of white-tailed deer ( Odocolieus virginianus) and Angora goats; two similar-sized ungulates with different digestive morphologies. I contrasted patterns in deer and goat foraging effort, diet composition and quality, and estimated nutrient ingestion rates (i.e., foraging efficiency) while animals ranged freely within 0.4 ha enclosures in two pastures at the Texas Agricultural Experiment Station (TAES) near Sonora during fall and summer. The pastures were under different management regimes and differed in plant composition and available standing crop. During trials, deer were highly mobile, traveling an average of 10 km during 12 to 16 hr of foraging per day. Goats exhibited less foraging effort, traveling approximately 4 km during 10 to 14 hr of foraging each day. Deer fed more selectively and made greater use of forbs and other uncommon forages (oak mast). Goat diets were dominated primarily by grasses and browse which were common in both pastures. Dry matter intake rates of both deer and goats varied considerably during feeding periods. During summer, goats averaged higher intake rates than deer in both pastures. Intake rates were more similar during fall when deer selectively consumed acorns. Deer and goat intake rates could not be predicted from the availability of plant biomass in pastures. Although deer diets generally contained more in vitro digestible organic matter than goat diets, concentrations of crude protein and digestible energy were similar between pastures and seasons. Surprisingly, feeding rates of deer and goats were consistently higher in pasture D which contained only half the standing crop found in the B pasture. Results from this study suggest that traditional approaches being used to assess habitat quality for ruminants may not accurately represent feeding opportunities for selective feeders.