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28th Annual Meeting and Symposium of the
Desert Tortoise Council, February 21-23, 2003
Abstracts
STUDENT PAPER
Desert Tortoise Reproduction and Home Range at Saguaro National Park, Tucson, Arizona
Eric W. Stitt1, Roy C. Averill-Murray2, Terry E. Christopher3,
Don E. Swann4, Cecil R. Schwalbe5, and Todd Esque6
1Wildlife and Fisheries Science, University of Arizona, 125 Biological Sciences
East, Tucson, AZ, 85721;
2Arizona Game and Fish Department, 2221 West Greenway Road, Phoenix, AZ,
85023;
3Smithsonian Institution, Las Vegas, NV;
4Saguaro National Park, 3693 South Spanish Trail, Tucson, AZ, 85730;
5U.S. Geological Survey, Southwestern Biological Science Center, Sonoran
Desert Field Station, Tucson, AZ, 8572;
6U.S. Geological Survey, Western Ecological Research Center, Las Vegas Field
Station, Henderson, NV
In 2001 and 2002, we studied reproduction in female desert tortoises at two sites at Saguaro National Park, in Tucson, Arizona by using ultrasound and x-radiography. We also tracked tortoises of both sexes regularly with radiotelemetry through the active season. Weather patterns were quite different between years, possibly leading to differences in reproductive effort. In 2001, following a period of above-average rainfall, 71% of monitored females developed egg clutches, and mean clutch size was 6.9 eggs (range, 1-9). In 2002, after an extended dry spell, 25% of monitored females produced egg clutches, and mean clutch size was 4.6 eggs (range, 3-6). There appears to be no correlation between midline carapace length (MCL) or sex and home range size. However, home range size appeared to vary between years, possibly as a response to changes in rainfall levels.