Range in California: Red
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Adult, San Bernardino County |
Sub-adult, San Bernardino County |
Adult, San Bernardino County, in defensive pose. |
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Adult, San Bernardino County |
Adult crossing a road in the late afternoon, San Bernardino County |
Adult, San Bernardino County |
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Old adult male, Riverside County |
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Captive adult. © Gary Nafis. Specimen courtesy of Ed Pirog |
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Captive juvenile. © Gary Nafis. Specimen courtesy of Ed Pirog |
Hatchling, rescued from raven predation, San Bernardino County © Bill Ford |
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Juvenile, San Bernardino County
© Aaron Wells |
Tortoise in habitat, Riverside County |
Tortoise in the mouth of a burrow, San Bernardino County. © Kate Britsch |
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Captive juvenile. © Gary Nafis. Specimen courtesy of Ed Pirog |
Ravens prey heavily on juvenile Desert Tortoises. Due to their ability to take advantage of garbage and other food sources found around human settlements, the raven population has been booming in the desert. The spikes on this fence illustrate one of the methods used to discourage these native birds from roosting near protected tortoise habitat. |
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Habitat |
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Entrance to burrow, Kern County |
Entrance to burrow, Kern County |
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Habitat, Creosote flats, Kern County |
Habitat, San Bernardino County |
Habitat, San Bernardino County |
Tortoise Signs |
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Protected habitat, Imperial County |
Tortoise illustrations, Desert Tortoise Natural Area, Kern County
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Short Video |
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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. |
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| 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 |
Ranges from Southern Nevada and extreme southwest Utah west through southeastern California, and east through southern Arizona, to northern Sinaloa Mexico.
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. |
| 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 |
| No subspecies have been designated, however, various populations show some chemical differences and attempts have been made to describe new taxa. |
| 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. |
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Taxonomy |
| Family |
Testudinidae |
Land Tortoises |
| Genus |
Gopherus |
Gopher Tortoises |
Species
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agassizii |
Desert Tortoise |
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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
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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
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Alternate Names |
None that I know of.
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Related or Similar California Turtles |
A. m. pallida - Southern Pacific Pond Turtle
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More Information and References |
Natureserve Explorer
California Dept. of Fish and Game
Desert Tortoise Preserve Committee
Center for Biological Diversity
Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.
Behler, John L., & F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.
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.
Lemm, Jeffrey. Field Guide to Amphibians and Reptiles of the San Diego Region (California Natural History Guides). University of California Press, 2006.
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The following status listings come from the Special Animals List which is published several times each year by the California Department of Fish and Game.
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Organization
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Status Listing
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| U.S. Endangered Species Act (ESA) |
FT |
Threatened |
| California Endangered Species Act (CESA) |
ST |
Threatened |
| California Department of Fish and Game |
None |
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| Bureau of Land Management |
None |
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| USDA Forest Service |
None |
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| Natureserve Global Conservation Status Ranks |
G4 S2 |
Apparently Secure |
World Conservation Union - IUCN Red List
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IUCN:VU |
Vulnerable |
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