Twenty-Third Annual Meeting and Symposium of the
Desert Tortoise Council, April 3-5, 1998
Abstracts

Desert tortoise reproduction was monitored by radiography at two sites in the Sonoran Desert in 1997. At Sugarloaf Mountain, Maricopa Co., Arizona, 12 telemetered tortoises were radiographed weekly from 15 May to 12 August. Tortoises were also radiographed on 12 September and 21 October. Four tortoises were determined to be gravid, with clutch sizes ranging from two to five eggs (mean = 3.75). At the Granite Hills, Pinal Co., Arizona, non-telemetered tortoises were located and radiographed, as often as possible, during weekly trips from 4 June to 14 August. Eggs were detected in four tortoises, with clutch sizes ranging from one to five eggs (mean = 3.25). Oviposition at both sites occurred before and during the summer monsoon season, from early May to late August. Below average winter-spring rainfall in 1996-97 at Sugarloaf may have contributed to low reproductive output compared to 1993 (eight of 10 females laying eggs, 5.7 eggs/clutch), which was preceded by above average winter-spring rainfall.