DESERT TORTOISE COUNCIL

Working to assure the continued survival of viable populations of the desert tortoise throughout its range

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


Desert Tortoise Reproduction at Two Sites in the Sonoran Desert

Eric W. Stitt,1 Roy C. Averill-Murray,2 Terry E. Christopher,3
Don E. Swann,
4 and Cecil R. Schwalbe5

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, 8573; and
5U.S. Geological Survey, Sonoran Desert Field Station, Tucson, AZ, 8572

 

In 2001, we studied the reproductive effort for female desert tortoises at two sites in the Sonoran Desert. We monitored female tortoises from May to October by using ultrasound and x-radiography. At Sugarloaf, 60% (9 of 15) of mature (Midline Carapace Length >220 mm) females developed eggs. None of three individuals <220 mm (187-199 mm) produced eggs. Mean clutch size was 5.3 eggs (range, 4-9). At Saguaro National Park, we monitored 14 female tortoises. Of these, 71% developed egg clutches. Mean clutch size was 6.9 eggs (range, 1-9). At both sites, ovarian follicles were observed in early May, and all clutches were deposited by August 9. We monitored two nests throughout the incubation period. One failed to hatch; the other produced 7 neonates. All neonates were small (mean mass = 12.4 g, average MCL = 36.7 mm), and most failed to survive.

 

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