Laboratory Health Profiles
of Desert Tortoises in the Mojave Desert:
A Model for Health Status Evaluation of Chelonian Populations
P L E N A R Y L E C T U R E
MARY M. CHRISTOPHER,1 KEN A. NAGY,2
IAN WALLIS,3 JAMES K. KLAASSEN,2 AND KRISTIN H. BERRY 4
1 University of CaliforniaDavis, Davis, CA 95616 USA
2 University of California, Los Angeles, CA 90024, USA
3APL Laboratories, Las Vegas, NV 89119, USA
4 U.S. Geological Survey, Biological Resources Division, Riverside, CA 92507-0714, USA
ABSTRACT: Survival of the desert tortoise, Gopherus agassizii, in todays world depends upon its ability to adapt to drought, habitat loss, competition for forage, and our ability to detect and eradicate diseases such as mycoplasmosis. In 1989, the Bureau of Land Management instituted a Laboratory and Health Profile Research Program designed to analyze and interpret laboratory and health data from free-ranging desert tortoises over a 35 year period. The goals of this program were to establish reference ranges under a variety of environmental and physiological conditions, to differentiate physiologic and pathologic changes, and to assess the utility of specific laboratory tests for evaluating desert tortoise health. Between 1989 and 1992 blood samples were obtained for hematological and biochemical profiles from tortoises at three sites in the Mojave Desert of California. Physical examinations, nasal cultures, and serology for Mycoplasma agassizii were also performed and interpreted in conjunction with changes in laboratory data.
The first year of the program was a trial during which sampling protocols, test parameters, methodology, and data formats were optimized. Consistent data that permitted year-to-year comparisons were obtained between 1990 and 1992. Significant differences were observed in several parameters between male and female tortoises. Marked seasonal differences were observed in association with hibernation, rainfall, and dietary intake. Urea nitrogen was the best overall indicator of hydration status. Marked elevations in blood urea nitrogen occurred during a drought year and were associated with significant mortality in tortoises at one study site. Plasma iron, glucose, and total protein values were good longitudinal indicators of nutritional status, and values were often lower in tortoises serologically positive for M. agassizii. Individual tortoises showed laboratory and physical evidence for anemia, renal failure, and inflammatory disease. These results support the need for baseline laboratory and health data to assess the effects of environmental degradation, physiological changes, and disease exposure, as well as to monitor both immediate and long-term changes in population health.
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