27th Annual Meeting and Symposium of the
Desert Tortoise Council, March 22-24, 2002
Abstracts

Proposed Physiological Studies on Desert Tortoises at Fort Irwin, California

Michael P. O'Connor
Department of Bioscience and Biotechnology, Drexel University, Philadelphia, PA 19104

Desert tortoises are ectothermic herbivores that face a series of challenges in their environment including both the rigors of their xeric and often thermally inhospitable habitat, anthropogenic effects (habitat destruction and disturbance) and a range of diseases. As part of the management planning for desert tortoises, three independent population viability analyses have been done. Those analyses are unanimous in noting that one of the fundamental problems with the analyses, and hence with the management plans, is the lack of data allowing one to match temporal and spatial variation in habitat characteristics to variation in demographic rates of tortoises. Our studies aim to create such linkages by proposing that habitat characteristics strongly affect the activity, thermal, hydric, and energy/resource budgets of tortoises and that those budgets play a significant role in determining the demographic rates of tortoises. We choose to focus initially on how environmental characteristics and disease (seroreactivity to Mycoplasma) affect the activity, hydric, and energetic budgets of tortoises in several sites. We will examine the relationships between those budgets and the vital rates (growth, reproduction and survivorship) of the tortoises. The study will be conducted and the vital rates measured in conjunction with a tortoise demography study already ongoing at Ft. Irwin, CA. In addition to the factors cited above, we will attempt to address the effect of the Army's training activities on both the tortoises' physiological states and vital rates by selecting sites that experience varying intensities of training activities (including no activity). This information may be used by the study's sponsor (Ft. Irwin, DOD) to guide tortoise management efforts.