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- G. agassizii: north and west of the Colorado River in the Southwestern United States in the Mojave and western Sonoran Deserts in California, southern Nevada, northwestern Arizona, and southwestern Utah (Murphy et al. 2011)
- Small subpopulation found east of the Colorado River in the Black Mountains of northwestern Arizona.
- Found up to 1570 m elevation
- Population estimates difficult to accurately describe due to patchy distribution and difficulty of detection
- Appearance of upper respiratory tract diseases, shell disease, habitat destruction, degradation, and fragmentation have all contributed to declining populations (IUCN 2020)
- G. morafkai found in US and Mexico inhabiting Arizona south and east of the Colorado River, Sonora (including Isla Tiburon), and extremem northern Sinaloa (Murphy et al. 2011, Rhodin et al. 2018)
- G. evgoodei is endemic to Mexico occurring in southern Sonora, northern Sinaloa, and extreme southwestern Chihuahua (Edwards et al. 2016, Rhodin et al. 2018)
Previous range descriptions (Van Devender 2002)
- Western California
- Southern Nevada
- Far southwestern and western Arizona
- Far southwestern tip of Utah
- Sonora and Sinaloa, Mexico
- Including Tiburón Island, Gulf of California (Osorio & Bury 1982)
- Possibly Chihuahua
- Populations separated into Mojave and Sonoran deserts: (Lamb & McLuckie 2002)
- Mojave tortoises north and west of Colorado River
- Sonoran desert population: south and east of Colorado River (Arizona and Mexico)
(Van Devender 2002)
- Desert scrub
- Foothills thorn scrub
- Tropical deciduous forest/coastal thorn scrub
- Sea level to 2,225 m (7,300 ft); best habitats at 305-914 m (1,000-3,000 ft)
- Three population assemblages: (Berry 1990)
- North and west of Colorado River/Grand Canyon - valleys and alluvial fans in creosote bush/yucca communities with good soil for digging and adequate forage
- South and east of Colorado River/Grand Canyon - steep, rocky slopes of mountains in palo verde-cactus communities
- In Mexico - thorn scrub and oak woodland communities.
- Habitats occupied Sonoran Desert: usually steep and east-facing (Zylstra & Steidl 2009)
- Shelter-sites most often utilized in naturally exposed caliche along washes or rock fractures. (Zylstra & Steidl 2009)
- Lower alluvial slopes of desert mountain ranges, in valleys between ranges (Riedle et al 2008)
- Habitats occupied in Mojave Desert: (Zylstra & Steidl 2009) (U.S. Fish and Wildlife Service 1994)
- Traditionally described as occupying flats and bajadas; also slopes up to juniper woodlands
- Soils may be important aspect to habitat; loamy soil (suitable for digging) preferred (Anderson et al 2000)
- Suitable plant cover, especially creosote bush communities (Larrea tridentata), along with annual and perennial grasses and cacti. (Ernst & Lovich 2009)
- Elevations 1,500 to 1,600 m (4921 to 5,249 ft); on occasion up to 2,000 m (6,562ft) (Ernst & Lovich 2009)
- Habitats in Mojave Desert have more irregular rainfall, limited resources (Curtin et al 2008)
- Plant communities dominated by creosote bushes (Larrea tridentata) and burro bushes (Ambrosia dumosa) (Ernst & Lovich 2009)
- Habitats in Sonoran Desert's rainfall is more predictable, resources more abundant. (Curtin et al 2008)
Desert Tortoise Distribution
Desert tortoises, G. agassizi, live in the southwestern United States.
Adapted from www.d-maps.com according to Nevada Fish & Wildlife fact sheet. Click here for on map for detailed distribution (IUCN).
Also see pg. 8 of Annotated Bibliography and Data Basin, which uses USGS data for some maps.
Desert tortoises rely on the rocky substrates for shade and protection from predators.
Image credits: © San Diego Zoo Wildlife Alliance. All rights reserved.
Anderson et al. (2000)
Curtin et al. (2008)
Ernst & Lovich (2009)
Lamb & McLuckie (2002)
Murphy et al. (2011)
Osorio & Bury (1982)
U.S. Fish and Wildlife Service (1994)
Van Devender (2002)
Zylstra & Steidl (2009)
SDZWA Library Links
Fact Sheet Index
Fact sheet index, San Diego Zoo Wildlife Alliance Library
Home page, San Diego Zoo Wildlife Alliance Library
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