Ravens are known to prey on hatchling Desert Tortoises. The birds are natural desert residents, but their numbers have been increasing due the increased amount of food available in the garbage from the human settlements which have steadily encroached onto tortoise habitat. The spikes placed on top of these fence poles illustrate one of the methods used to discourage ravens from roosting near protected tortoise habitat.
A large, slow-moving, terrestrial desert turtle with a high domed shell composed of large scutes marked with many growth lines, large elephantine rear feet, and stocky forelimbs covered with large conical scales.
The carapace is unkeeled, with a serrated rear rim.
Color and Pattern
Color is tan, brown, grayish brown, to blackish and usually without any pattern.
The scutes may brownish or orange centers, particulary on young individuals.
Skin on the limbs and head is brownish, and the limb sockets and neck skin are yellowish. The plastron is unhinged and yellow or brownish in color.
Male / Female Differences
Males are larger than females with a concave plastron, a longer, thicker tail, and massive claws.
chin glands on each side of the lower jaware larger on males.
The gular shields (throat shields - on the front of the shell below the head) are longer on males.
Young have a flexible shell, long sharp nails, and a lighter carapace than adults.
Color is dull yellow to light brown with dark borders around the shields.
Life History and Behavior
Terrestrial, spending most of its life in underground burrows.
This tortoise can live up to 50 years, possibly as long as 80 years.
The feeding and activity period of this species is very short, and mostly restricted to spring.
Most active during the day in spring, early summer, and during summer rains, becoming more active in early morning and late afternoon as seasonal temperatures increase. There may be another period of activity in the early fall as new sprouts germinate.
Winter hibernation begins from October to November, and often occurs in a communal den.
During the cold of winter, the heat of summer, or very dry years, a tortoise remains in a underground burrow which provides it with a more constant temperature and higher humidity. Tortoises dig the burrows in dry gravelly, or sandy soil often at the base of a bush. The burrows are she shape of a half circle, and typically measure 3 - 9 feet long, but have been measured at 30 feet long in the colder part of its range. Different burrows are constructed for different purposes. Spring burrows are shallow. During spring tortoises may simply rest under a shaded bush. Summer burrows are typically shorter and dug on flat ground, while wintering dens are longer and often dug at the top of a steep bank.
Desert tortoises are subject to dehydration due to loss of water through evaporation and urination. Tortoises will drink water when it is available during infrequent rains, but when water is not available, they rely on water stored in the bladder. When frightened, especially when picked up, a Desert Tortoise will often void the contents of its bladder, putting it at risk of dehydration.
Desert Tortoises exhibit some interesting social behaviors, including head bobbing when two tortoises meet, male combat and other territorial behavior, including vocal sounds and hissing.
A Desert Tortoise may live as long as 150 years. Adults become sexually mature at 15 - 20 years.
Native Americans used Desert Tortoises for food. A tortoise was placed on its back on a fire. When the shell cracked, the tortoise was ready to eat.
Diet and Feeding
Eats plant material such as grass, cactus, herbs, flowers, and legumes. Non-native plants are rarely eaten. The most important plants in the diet are annual plants, which have a life span of only about a month, and are only available from April to June.
The annual feeding period may last only last from 6 - 12 weeks in a good year, and good years only occur on an average of one in five years.
Courtship and breeding occur soon after emergence from hibernation in March and April. Males combat each other for access to females, using their enlarged gular horns to ram and possibly overturn another tortoise.
A tortoise that cannot right itself, is in danger of dying from overexposure to the sun.
Females lay a clutch of 1 - 12 eggs from May to July, usually at the opening of or just inside a burrow.
1 - 3 clutches might be laid in favorable years.
The eggs hatch from mid August to October.
A desert species that needs firm ground in order to dig burrows, or rocks to shelter among.
In California it is found in arid sandy or gravelly locations along riverbanks, washes, sandy dunes, alluvial fans, canyon bottoms, desert oases, rocky hillsides, creosote flats and hillsides.
The species previously known as Gopherus agassizii was split into two species:
Gopherus agassizii occurs only in California, extreme southern Nevada, extreme southwest Utah, and extreme northwest Arizona;
Gopherus morakfai occurs from Southern Nevada and extreme southwest Utah east through much of western Arizona, and south along the Pacific Coast of Mexico to northern Sinaloa.
Range In California
The Mohave Desert Tortoise is found throughout the Mojave Desert and south along the Colorado river and along the east side of the Salton Basin in Sonoran Desert. Absent from the Coachella Valley.
There is an introdued population
of Desert Tortoises in Anza-Borrego State Park, San Diego County. (There is a picture of one above.) I have not yet found anything in print that explains their presence there. According to comments by Jeff Lemm in his field guide to reptiles and amphibians in San Diego County (2006) the Desert Tortoise "...is rarely seen in San Diego County. Specimens in San Diego County are believed to be introduced once-captive animals and their offspring (K. Berry, pers. comm.)"
On a March 2015 flickr page naturalist Donald Endicott, co-author of 50 Best Short Hikes San Diego, posts a picture of a tortoise he photographed at Anza-Borrego State Park and writes that pet tortoises were intentionally released into the area in 1970 and 1971 to repatriate them and to establish a reserve for the species in a suitable habitat, but he does not provide a source for the information.
Stebbins & McGinness (2012) comment that the Desert Tortoise "...is absent from the Coachella Valley except from the Boyd Deep Canyon Research Center area. The historical situation in this valley may be confusing because of escaped or released pet tortoises."
Notes on Taxonomy
'The spelling of the word "Mojave" or "Mohave" has been a subject of debate. Lowe in the preface to his "Venomous Reptiles of Arizona" (1986) argued for "Mohave" as did Campbell and Lamar (2004, "The Venomous Reptiles of the Western Hemisphere"). According to linguistics experts on Native American languages, either spelling is correct, but using either the "j" or "h" is based on whether the word is used in a Spanish or English context. Given that this is an English names list, we use the "h" spelling (P. Munro, Linguistics, UCLA, pers. comm.).'
(Taxon Notes to Crotalus scutulatus, SSAR Herpetological Circular no 39, published August 2012, John J. Moriarty, Editor.)
Robert W. Murphy, Kristin H. Berry, Taylor Edwards, Alan E. Leviton, Amy Lathrop, and J. Daren Riedle, in a June 2011 publication * found that the original publication date for the description of Xerobates agassizii, Agassiz Land-Tortoise, which was given as 1863, was actually 1861 and that the specimen was from California, not Arizona.
Citing significant differences in DNA and morphological, physiological, and ecological characteristics, they determined that Gopherus agasizii consists of two species, which they name Gopherus agassizii and Gopherus morafkai. G. morafkai represents the tortoises formerly classified as G. agassizii occurring east and south of the Colorado River in Arizona, and western Mexico. G. agasizii represents those tortoises occurring west and north of the Colorado River, in California, Nevada, Utah, and Arizona. They suggested the common names Agassiz's Desert Tortoise for G. agassizii, and Morafka's Desert Tortoise for G. morafkai, but the SSAR wisely decided to support the recognition of the traditional geographic standard names - Mohave Desert Tortoise, and Sonoran Desert Tortoise.
[In my opinion all species common egocentric names derived from possessive family names - Cope's, Morafka's, Skilton's, etc., should be replaced with a more appropriate common name that represents either a geographic region or a special characteristic of the animal. I think it honors history enough to use a person's name only in the Latin.]
Listed as a threatened species by the state and federal governments. The Desert Tortoise population has declined significantly due to human activity in the desert. Military land development, urban development, off-road vehicle use, mining, overgrazing, agricultural development, intrusion of non-native plants, and Upper Respiratory Tract Disease have all been pointed out as probable causes for this decline. In addition, urban development of the desert leads to an increase in sources of food and water, including garbage, that are used by native ravens, allowing them to increase their numbers. The Desert Tortoise suffers with this population increase because ravens prey on young tortoises. Release of captive pet Desert Tortoises has also been considered detrimental.
The discovery that the desert tortoise actually consists of two unique species reduces the geographic range of G. agassizii to around 30 per cent of its former range which heightens the need for the conservation of the species.
According to the group Defenders of Wildlife, the tortoise population in the western Mojave Desert has declined by 90 percent since the early 1980s. Military bases in the area with healthy tortoise populations
have been charged with protecting the tortoises by monitoring their health and conducting training exercises away from tortoise-heavy areas. Large-scale tortoise relocation efforts have also been attempted, and more have been planned, but after it was learned that more than 30 percent of tortoises relocated died in a 2008 relocation project at Fron Irwin, the effectiveness of relocation has been debated. A study conducted by Federal officials blamed a drought for the tortoise deaths, claiming that 30 percent of non-relocated tortoises also died in the drought, but Environmental groups disputed the finding. Fish and Wildlife Service biologist Brian Croft, who has dealt with the problems of relocating tortoises, says that as long as translocation is planned properly, it can be successful. (Washington Post 6/28/16)
Official California State Reptile
The legislation was proposed by students at the Benjamin Bubb School in Mountain View and sponsored by Assemblyman Richard D. Hayden of Sunnyvale.
It was made law in 1972. Being an official state reptile still doesn't protect you from bulldozers, so I'm not sure what good it is.
Mohave Desert Tortoise
Gopherus agassizii - (Cooper, 1863) - Proc. California Acad. Sci., Vol. 2, p. 120
According to James R. Buskirk, the meaning of the word "gaufre" in French is honeycomb, not a small burrowing animal. "The word may thus refer to the anastomosing tunnels of these fossorial chelonians," or an "alternative explanation for the origin of Gopherus is that it is derived from a West African word for chelonian, mungofa."
* Murphy RW, Berry KH, Edwards T, Leviton AE, Lathrop A, Riedle JD (2011) The dazed and confused identity of Agassiz’s land tortoise, Gopherus agassizii (Testudines, Testudinidae) with the description of a new species, and its consequences for conservation. ZooKeys 113: 39–71. doi: 10.3897/zookeys.113.1353
Stebbins, Robert C., and McGinnis, Samuel M. Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012.
Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972.
Samuel M. McGinnis and Robert C. Stebbins. Peterson Field Guide to Western Reptiles & Amphibians. 4th Edition. Houghton Mifflin Harcourt Publishing Company, 2018.
Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.
Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.
Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998.
Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Turtles and Lizards of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009.
Carr, Archie. Handbook of Turtles: The Turtles of the United States, Canada, and Baja California. Cornell University Press, 1969.
Ernst, Carl H., Roger W. Barbour, & Jeffrey E. Lovich. Turtles of the United States and Canada. Smithsonian Institution 1994.
(2nd Edition published 2009)
Lemm, Jeffrey. Field Guide to Amphibians and Reptiles of the San Diego Region (California Natural History Guides). University of California Press, 2006.
The following conservation status listings for this animal are taken from the November 2020 California "Special Animals List" and the November 2020 "State and Federally Listed Endangered and Threatened Animals of California" list, both of which are produced by multiple agencies and available here: https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals. You can check the link to see if there are more recent lists.
If no status is listed here, the animal is not included on either list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status you can go to the NatureServe and IUCN websites to check their rankings.
NatureServe Global Ranking
Vulnerable—At moderate risk of extinction due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors.
NatureServe State Ranking
Imperiled - Vulnerable
U.S. Endangered Species Act (ESA)
Listed as Threatened 4/02/1990
California Endangered Species Act (CESA)
SCE - 10/19/2020
Listed as Threatened 8/03/1989
Candidate for Endangered Species 10/19/2020