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| The Desert Tortoise t is one of
4 species of the genus Gopherus, known collectively
as gopher tortoises. Gopher tortoises have brown shells 8
-to 15 inches long with flattened front limbs adapted for
burrowing. The Sonoran Desert Tortoise is flat and pear-shaped
compared to the Western Mojave tortoise which is more butterball
shape. Desert Tortoises can weigh up to 15 pounds. |
Western Mojave Tortoise
Notice the butterball shape |
| The Tortoise's
hind limbs differ markedly from the forelimbs. Whereas the
hind limbs are elephantine, the forelimbs are flattened with
well-developed muscle. They are used for digging burrows.
The females use their hind limbs to dig their nests. |
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Desert Tortoise in natural
habitat |
Desert tortoises inhabit semi-arid
grasslands, gravelly desert washes, canyon bottoms and rocky
hillsides. In the Sonoran Desert of Arizona, however, the
tortoises tend to live on steep, rocky hillside slopes in
Palo Verde and Saguaro Cactus communities. |
| Northern Desert Tortoise
populations are most common at elevations of 2,300 to 4,000
feet, while the Sonoran populations generally live at 2,300
to 3,500 feet. Creosote bush, burrobush, mojave yucca and
blackbrush are usually found in Desert Tortoise habitat. At
higher altitudes, joshua tree and galleta grass (Pleuraphis
rigida) are common. |
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| The diet
of the Desert Tortoise is comprised of herbs, grasses, some
shrubs and the new growth of cacti and their flowers. The
Desert Tortoise may go for many years without drinking, getting
most of their water from plants and then storing it in their
bladders. |
Munching Lunch |
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Tortoises can vocalize and
make hisses, long calls, pops and "poink" noises. Scientists are
not sure what the various noises mean or why the tortoises make
them. Studies indicate that tortoises may have both fear vocalizations
and distress calls. Males tend to grunt when mating. They may also
make sounds can't hear because the sounds are either too high or
too low for the human hearing range.. |
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Desert tortoises live long
and pretty solitary lives. They spend about 93 to 95 percent of
their lives underground. They hibernate from October or November
until February or March, usually in separate burrows. Hibernation
for a tortoise is a period of inactivity, generally below ground
in a burrow or den. The body temperature is lowered and is close
to that of the air temperature in the burrow, about 40° F to
60° F. The heart rate, respiration rate and all bodily processes
are slowed. Tortoises usually do not emerge from the burrow during
hiberrnation except to drink water when it is available. |
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Male Tortoises generally
court female tortoises whenever the opportunity presents itself,
e.g., in spring, summer, or fall. There does not appear to
be a well defined "mating season."
females usually lay one or more clutches
of 1 to 14 eggs between mid-April and the first week of July.
The size of the clutch depends on the size of the female,
with small females producing smaller clutches than the larger
females. Females dig the nests with the hind legs and drop
the eggs into the nest, placing them with the hind legs and
covering them carefully. The location of an undisturbed nest
cannot be detected by humans. Nests are most often associated
with the female's burrows. The nest may be in the burrow mound,
the mouth of the burrow, or deep inside the tunnel.
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Female laying
eggs
Hatchlings emerging from eggs |
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Predators of the Desert Tortoise
vary depending on the age and size of the tortoise. There are egg
predators, such as the gila monster, kit fox, coyote, and badger.
Predators of juveniles include ravens, roadrunners, some snakes,
kit foxes, bobcats, badgers, coyotes, and probably the spotted skunk.
Larger tortoises are more likely able to resist
predation. Large tortoises may be eaten by kit foxes, badgers, bobcats,
coyotes and golden eagles. The large mammalian predators are not
likely to eat tortoises unless other food sources, such as rabbits
and rodents, are in short supply. Coyotes and kit foxes may dig
tortoises out of their burrows to eat. These predators can eat the
tortoise without breaking open the shell. |
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Some interesting facts about
Desert Tortoises are:
1. The Desert Tortoise is able to live where
ground temperature may exceed 140 degrees F.
2. 95% of a Desert Tortoise’s life is
spent in underground burrows!
3. Ravens have caused more than 50 percent
of juvenile Desert Tortoise deaths in some areas of the Mojave Desert!
4. Adult tortoises may survive a year or more
without access to water!
5. Desert Tortoise populations have declined
by 90 percent since the 1980s.
6. It is unlawful to touch, harm, harass or
collect a wild Desert Tortoise. |
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