The Llano River Watershed is located on the Edward Plateau of Central Texas, a region called the Hill Country. It is a healthy, productive ecosystem. However, the watershed is receiving more pressure from invasive plants and wildlife, which is negatively impacting riparian zones. A degraded state can lead to erosion and reduction in water quality and flow, which in turn impairs riparian function. One contributor to the riparian damage is the nonnative axis deer (Axis axis). Axis deer are also competing with the native whitetail deer (Odocoileus virginianus). The main objective of this research was to analyze and compare axis deer diet composition through DNA metabarcoding of fecal and rumen samples at the South Llano River State Park and Texas Tech University at Junction field station. Metabarcoding was done by Jonas Ventures. A secondary objective was to observe axis deer behavior. Fecal samples were obtained from known bedding areas, as well as directly observing and collecting material. Rumen samples were collected from deceased (road kill) axis deer. During observations, behaviors were categorized into seven actions: rest, stand, walk, run, social, alert, and forage. Individuals were observed for 120 seconds and consumption of grass, forb, or browse material was annotated.
Results/Conclusions
Deer spent most of their time foraging in the morning (40%) and evening (37%). Midday foraging was observed 23% of the time. Partitioning behaviors into specific habitats indicated that deer foraged 37% of the time in riparian zones, 45% in fields, and 18% in forests. Direct observations of foraging type were 57% of the time for grass, 37% for shrubs, and 6% for forbs. Metabarcoding the field station fecal samples indicated that 32% of protein is derived from Carya illinoinensis (pecan). This was followed by Carlowrightia texana (Texas wrightwort) at 31% and genus Prosopis (mesquite) at 5%. The top three species in the state park samples included pecan (35%), mesquite (10%), and Texas wrightwort (9%). Although these results don’t reflect the amount of biomass taken from the ecosystem, it shows how important protein from the pecan plant is for axis deer. This consumption, tied to high foraging in riparian zones, may lead to further erosion along the riverbanks and hamper recruitment of next generation riparian forest development. Further research needs to be done on axis deer seasonal diets as well as biomass removed from the ecosystem to understand the annual impact axis deer have on the watershed and whitetail deer.