Pima County: 2024 tortoise monitoring finds most plots occupied, disease incidence low

Dr. Melissa Van Clickhan, ecological monitoring program coordinator for Pima County's Conservation, Lands and Resources Department, presented findings from the county's 2024 Sonoran Desert tortoise monitoring in Tucson Mountain Park, saying 44 individual tortoises were captured and marked on 15 of 20 long‑term study plots during the summer monsoon season.

The county monitors tortoises as part of implementation of the Sonoran Desert Conservation Plan and its Multi‑Species Conservation Plan (MSCP), obligations the county said help mitigate impacts to covered species across the county's conserved lands. "It is actually just a dream job," Van Clickhan said, describing the fieldwork and the multi‑year survey design used to track occupancy, detection, colonization and extinction rates.

Van Clickhan told attendees the program uses 20 randomly generated plots across roughly 22,000 acres of modeled suitable habitat in Tucson Mountain Park, divided into units including Sweetwater Preserve, Painted Hills and Trails Park. Each plot is visited three times between July and September, producing 60 plot visits per monitoring year. The program has completed surveys in 2018, 2021 and 2024 and plans the next monitoring season in 2027.

Survey methods and results The county's field crews walk 17 transects per plot (each 170 meters long, 10 meters apart) and search under vegetation and in shelters, recording every tortoise…