Diet of desert tortoises at Yucca Mountain, Nevada, and implications for habitat reclamation

The diet of desert tortoises at Yucca Mountain was assessed during 1992 to 1995 using a combination of feeding observations and scat analysis. Feeding observation data (1993 through 1995) showed that tortoises fed on a wide variety of items. The most frequently eaten items were forbs and annual grasses. These two forage groups comprised more than 90% of all bites taken. Analysis of scat (1992 and 1993) also showed that grasses and forbs were the most common groups, making up more than 80% of the composition of scat. Yearly differences between proportions of species in the diet were observed and were most likely attributable to differences in plant productivity, which is linked to rainfall patterns. Non-native species were an important component of the diet in all years, accounting for 13 to 50% of all bites observed and 6 to 24% of scat contents. A list of all items encountered in the diet is provided. To facilitate reclamation of desert tortoise habitat disturbed by the Yucca Mountain Site Characterization Project, native forage species that should be included in reclamation seed mixes, when feasible, were identified. Although shrubs make up only a small proportion of the diet, they should also be included in reclamation efforts because they provide habitat structure. Tortoise cover sites, and microhabitats amenable to seed germination and seedling establishment. In addition, non-native species should not be planted on reclaimed sites and, if necessary, sites should be recontoured and soil compaction reduced prior to planting