Desert Tortoise
The nutrition lab has been investigating the nutritional needs of the desert tortoise, a threatened species, since 1991. The goals of the project are to determine the specific nutrient requirements of the tortoise, to ascertain which food plants meet those requirements, and to develop a means of assessing the availability of such foods in tortoise habitat.
There is a general concern that the precipitous decline in tortoise populations in some areas of the southwest may be related to inadequate nutrition, and that this in turn may be a consequence of human impacts, such as livestock grazing, weed introduction and off-road vehicle use, that have changed plant communities in the desert.
Research on captive tortoises is conducted at the Desert Tortoise Conservation Center, a tortoise holding facility southwest of Las Vegas. Tortoises displaced by development in the Las Vegas Valley are brought to the Center. If they are healthy, they are held at the Center until they can be released at a tortoise sanctuary south of the Las Vegas Valley. Field studies are done at various sites in southern Nevada as well as in adjacent California.
Recent studies have examined factors affecting the protein requirements of tortoises, the amounts of calcium and phosphorus tortoises need, and how the physiological adaptations of desert plants influence their nutrient composition. For example, desert plants often accumulate potassium as a means of enhancing water uptake from dry soils, and tortoises that eat them must use nitrogen (from protein) to excrete the excess potassium. We are also studying the food habits of tortoises in desert habitats and factors which influence food choice in captive tortoises.
