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A Guide to the Amphibians
and Reptiles of California


Mohave Desert Tortoise - Gopherus agassizii

(Cooper, 1863)
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Desert Tortoise Range Map
Historic Range in California: Red


observation link



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Desert Tortoise Desert Tortoise Desert Tortoise Desert Tortoise
Adult, San Bernardino County Sub-adult, San Bernardino County Adult, San Bernardino County,
in defensive pose.
Adult, San Bernardino County
Desert Tortoise Desert Tortoise Desert Tortoise Desert Tortoise
Adult crossing a road in the late afternoon, San Bernardino County Adult, San Bernardino County Old adult male, Riverside County
Desert Tortoise Desert Tortoise Desert Tortoise Desert Tortoise
Captive adult © Gary Nafis Specimen courtesy of Ed Pirog (STFU) Adult, San Bernardino County © Bill Ford
Desert Tortoise Desert Tortoise Desert Tortoise Desert Tortoise
Dry shells from expired tortoises, San Bernardino County © Jeff Ahrens
Desert Tortoise Desert Tortoise Desert Tortoise Desert Tortoise
Adult in burrow, San Bernardino County © Jeff Ahrens Adult in burrow, San Bernardino County © Jeff Ahrens Adult in burrow, San Bernardino County © Jeff Ahrens
Desert Tortoise Desert Tortoise Raven spikes  
This San Bernardino County adult tortoise was found stuck on some small rocks. It could not touch the ground with its front legs or push off with its back legs, though it probably would have worked itself free eventually. When a rock was removed, it was able to continue on its way. © Jeff Ahrens 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.  
     
Juveniles
Desert Tortoise Desert Tortoise Desert Tortoise  
Captive juvenile © Gary Nafis Specimen courtesy of Ed Pirog Juvenile, San Bernardino County
© Aaron Wells
 
Desert Tortoise Desert Tortoise    
Hatchling, rescued from raven predation, San Bernardino County © Bill Ford    
     
Desert Tortoise Scat
Desert Tortoise scat Desert Tortoise scat Desert Tortoise scat Desert Tortoise
Tortoise scat © Arthur Davenport

Tortoise scat © Michelle Tollett A handfull of tortoise scat © Jeff Ahrens Adult in burrow with scat, San Bernardino County © Jeff Ahrens
Desert Tortoise scat Desert Tortoise scat Desert Tortoise scat Desert Tortoise scat
A desert tortoise burrow with lots of scat and some egshell fragments
© Jeff Ahrens
Desert Tortoise scat © Jeff Ahrens Desert Tortoise scat © Jeff Ahrens Burrow and scat, San Bernardino County © Jeff Ahrens
       
Habitat and Burrows
Desert Tortoise Habitat Desert Tortoise Habitat Desert Tortoise Habitat Desert Tortoise Habitat
Entrance to burrow, Kern County Entrance to burrow, Kern County Habitat in spring during a wet year,
San Bernardino County
Desert Tortoise Habitat Desert Tortoise Habitat Desert Tortoise Habitat Desert Tortoise Habitat
Habitat, desert flats, Kern County Habitat, San Bernardino County Habitat, San Bernardino County Tortoise in habitat, Riverside County
Desert Tortoise Habitat Desert Tortoise Habitat Desert Tortoise Habitat Desert Tortoise Habitat
Habitat, San Bernardino County
© Jeff Ahrens
Burrow, San Bernardino County
© Jeff Ahrens
Habitat, San Bernardino County
© Jeff Ahrens
Tortoise in the mouth of a burrow, San Bernardino County © Kate Britsch
Desert Tortoise Habitat Desert Tortoise Habitat Desert Tortoise Habitat  
Tortoise burrows © Michelle Tollett  
   
Signs
Desert Tortoise Sign Desert Tortoise Sign Desert Tortoise Sign Desert Tortoise Sign
Desert Tortoise Sign Desert Tortoise Sign Desert Tortoise Sign Desert Tortoise Sign
Desert Tortoise Sign Desert Tortoise Sign Desert Tortoise Sign Desert Tortoise Sign
Desert Tortoise Sign Desert Tortoise Sign Desert Tortoise Sign Desert Tortoise Sign
Desert Tortoise Sign


   
Short Videos
Desert Tortoise Desert Tortoise    
A young Desert Tortoise walks along a rocky wash in the Mohave desert. Kicking dirt out behind it, an adult Desert Tortoise crawls back into its summer burrow.    
Description

Size
8 - 15 inches in shell length (20.3 - 38.1 cm). (Stebbins 2003)
Appearance
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 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.

Males are larger than females with a concave plastron, a longer, thicker tail, enlarged gular horns, massive claws, and larger chin glands on each side of the lower jaw.

Young have a flexible shell, long sharp nails, and a lighter carapace than adults. Colo is dull yellow to light brown with dark borders around the shields.
Behavior and Natural History
Terrestrial, spending most of its life in underground burrows. The feeding and activity period of this species is very short, and mostly restricted to spring. It is 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
Herbivorous. 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.
Reproduction
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.
Range
In California, it is found throughout the Mojave Desert south along the Colorado river and along the east side of the Salton Basin. Absent from the Coachella Valley.

Traditionally, when recognized as a single species, G. agassizii ranges from Southern Nevada and extreme southwest Utah west through southeastern California, and east through southern Arizona, to northern Sinaloa Mexico. But with the split into two species, it occurs only in California, and extreme southern Nevada, extreme southwest Utah, and extreme northwest Arizona.
Habitat
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.
Taxonomic Notes

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 suggest the common name Agassiz's Desert Tortoise for G. agassizii, and Morafka's Desert Tortoise for G. morafkai.

Conservation Issues  (Conservation Status)
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. Native ravens have fed very well on these food sources, allowing them to increase their numbers. The Desert Tortoise suffers with this population increase because ravens prey on young tortoises. Release of captive animals 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.
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.
Taxonomy
Family Testudinidae Land Tortoises Gray, 1825
Genus Gopherus Gopher Tortoises Rafinesque, 1832
Species


agassizii Mohave Desert Tortoise (Cooper, 1863)
Original Description
Gopherus agassizii - (Cooper, 1863) - Proc. California Acad. Sci., Vol. 2, p. 120

from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz

Meaning of the Scientific Name
Gopherus - French - gaufre - small burrowing animal - probably refereing to its burrowing habits.
agassizii
- honors Agassiz, Jean Louis R.

from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz

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."

Alternate Names
Desert Tortoise
Agassiz's Desert Tortoise

Related or Similar California Turtles
A. m. pallida - Southern Pacific Pond Turtle

More Information and References
California Department of Fish and Wildlife

Desert Tortoise Preserve Committee

Center for Biological Diversity

* 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.

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.


Conservation Status

The following status listings come from the Special Animals List and the Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.



Organization
Status Listing
U.S. Endangered Species Act (ESA) FT 4/02/90 Threatened
California Endangered Species Act (CESA) ST - 8/03/89 Threatened
California Department of Fish and Wildlife None
Bureau of Land Management None
USDA Forest Service None
 

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