Home Range, Spatial Overlap, and Burrow Use of the Desert Tortoise in the West Mojave Desert

Understanding the space use patterns of a population may provide crucial information regarding land management decisions, such as delineation of protected areas. Herein we provide a comprehensive analysis of factors affecting the space use of Desert Tortoises in the west Mojave Desert, including physical, social, and environmental variables. Our objectives were to determine how spatial overlap, as well as multiple parameters of burrow use, influence home range size of this species. Male tortoises were significantly larger than females and exhibited very different patterns of space and burrow use; however, body size did not affect these variables. Male home range (100% MCP) and core area (50% MCP) size averaged 65% and 73% larger than those of females. Burrow use by males and females affected core area size, but not home range area. Females exhibited a strong male bias in overlap of both estimates of space use and burrow sharing, while using a significantly lower number of burrows per year. However, males overlapped and shared burrows with a similar number of tortoises of either sex. In addition, a high degree of home range overlap between individuals suggests a lack of territoriality in this population, although this warrants further analysis. These results suggest that social factors may not be the primary determinants of space use in this Desert Tortoise population.