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Agassiz's desert tortoise and egg data from the Sonoran Desert of California (1997-2000, 2015-2018)

September 6, 2020

These data were compiled to evaluate reproductive output of Agassiz's desert tortoises (Gopherus agassizzi) in relation to environmental and individual-level variables. We collected data from four study sites in the Sonoran Desert of California, including two separate populations within Joshua Tree National Park, one population located on the northern versant of the Orocopia Mountains, and one population located at the extreme western end of the Coachella Valley. These data represent eight reproductive seasons that spanned over 20 years (1997-2000, 2015-2018). These data were compiled and added to a larger database with additional records collected by other scientists from eight other study sites in order to detect drivers of reproductive output in G. agassizii across its range. In our studies, mature female tortoises (straight-line carapace length ≥ 200 mm) outfitted with radiotransmitters were located and X-radiographed approximately every 10-14 days during the reproductive season (April-July). The appearance of shelled eggs on X-radiographs allowed for the determination of reproductive status, clutch sizes and number, and total annual egg production (TE). As a federally listed species, it is important to understand variables affecting desert tortoise reproductive ecology for effective management of the species.