Narrow ecological niches allow herbivores to coexist and overlap in habitat ranges with minimal interspecific competition. In species rich assemblages such herbivores in eastern Africa, large ungulates may change home ranges to access abundant vegetation. Herbivores including Grant's gazelle (Nanger granti) and Thomson's gazelle (Eudorcas thomsonii) share similar habitat requirements and live in sympatry despite the risk of interspecific competition. Both gazelles are mixed herbivores and rely on grasses and shrubs at different proportions. Studies have shown that Grant’s gazelle have a higher percentage of browsing plant material in their diet compared to Thomson’s gazelle which prioritize grasses. To test this, we assessed habitat usage and preference of both gazelle species based off habitat availability in Manyara Ranch, Tarangire National Park, and the controlled game areas of Mto wa mbu in northeast Tanzania. Throughout the dry, long rain, and short rain seasons, we conducted mammal assessment surveys using 2km transects every 500m to record each species sighting, habitat type, and location. Based off their diet preferences, I hypothesize that Grant's gazelle will have a greater preference for habitats with greater woody plant cover while Thomson’s gazelle will favor habitats dominated by grasses.
Results/Conclusions
We used the Jacob’s index to calculate which habitats were selected by using the proportion of sightings in a given habitat type and the proportion of available habitat. Our results revealed that habitat preferences were dependent on seasonality. Grant’s gazelles were more common year-round in shrublands and grasslands, but there was a preference to shrublands during the dry season and bushlands and grasslands during rainy seasons. Thomson’s gazelles preferred grasslands in dry seasons and switched to shrublands and grasslands in wet seasons. This generally supports the initial hypothesis that the gazelles are found in areas where there are abundant food resources based on their diet. Further work can quantify the differences in consumed plant material between the species to get a better understanding between their diet preferences.