Factors Affecting Space Use, Habitat Use, and Landscape Connectivity for Sonoran Desert Tortoises (Gopherus morafkai) in Southern Arizona

The Sonoran desert tortoise (Gopherus morafkai) is a terrestrial, herbivorous reptile that exists throughout most of the Sonoran Desert of North America. The species faces various threats, many of which are driven by human activity (Averill-Murray et al. 2023). Throughout much of the species’ range, climate change, drought, wildfire, habitat loss and fragmentation, the spread of invasive species, urban development, and the development of transportation infrastructure threaten the species’ long-term persistence (Esque et al. 2002; Howland and Rorabaugh 2002; Edwards et al. 2004; Gray et al. 2015; Carter et al. 2020; USFWS 2021; Averill-Murray et al. 2023). Additionally, the species’ range is split by the United States – Mexico border wall, with 62% of habitat in Arizona, USA and 38% in Sonora, Mexico. In Arizona, the species faces additional threats like off-road vehicle use and renewable energy (e.g., solar) development (Fleckenstein et al. 2025). In Sonora, agricultural practices (e.g., grazing) are replacing tortoise habitat (Averill-Murray et al. 2023). Many of these anthropogenic activities, in addition to degrading, removing, and fragmenting habitat, may be reducing landscape connectivity within and among habitat patches and populations (Howland and Rorabaugh 2002; Edwards et al. 2004; Sutor et al. 2023; Sutor et al. 2024). In response to growing concerns over the species’ future, the species was listed as “Vulnerable” following an IUCN Red List assessment in 2023 based on evidence that the species’ populations are declining and its geographic distribution is shrinking (Averill-Murray et al. 2023). For other North American tortoises (genus Gopherus), namely those species or populations already protected under the U.S. Endangered Species Act, numerous studies on what influences tortoise movement, home range size, landscape connectivity, and gene flow have helped develop or refine management actions targeted at mitigating the effects of anthropogenic activities (e.g., Hromada et al. 2020). Yet, for G. morafkai, such studies remain few. Furthermore, these studies represent a limited portion of this species’ extensive range. In this dissertation, I present the results of three studies that aim to contribute to the body of literature on the species’ habitat use and home range characteristics, as well how linear barriers to tortoise movement (e.g., highways and canals) influence landscape connectivity throughout the species’ range.