Investigation

The Effects of the Environment on Desert Tortoises

Introduction:

    The desert tortoise has many unique characteristics.  These include its ability to burrow into the ground to escape the summer heat. Most of these characteristics, both physical and behavioral, were developed to help them in their environment. They are interesting because most of their life is spent underground;  they are only on the surface about five percent of their unusually long lives. All these characteristics, strange as some may seem, all serve a very important purpose; they all allow the tortoise to survive in the Sonoran Desert.


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Basic Things to Know:

    An average tortoise weighs 8-15 pounds, is 9-15 inches long, and 4-6 inches high. They have a long lifespan for a creature of their size - between 80 and 100 years, which is longer than the average human's lifespan (70 to 80 years). They are found in the Mojave and Sonoran Deserts in southeastern California, southern Nevada, and south through Arizona into Mexico. It is one of 4 species of the genus Gopherus.

Adaptations:

    There are many amazing things about the desert tortoise that many people aren't aware of. One thing most people don't know is that they can live in area where the ground temperature exceeds 140ºF. They are able to do this because they can use their strong and muscular forelimbs for burrowing into the ground where it is cooler. Ninety-five percent of a tortoise's life is spent in the ground escaping the heat. Tortoises hibernate from November to February or March. When they aren't hibernating, they usually come out just after it has rained. Adults can live a year without water, which is important because of the lack of water in the desert. They have adapted their bodies so that water that reaches the bladder is not lost but can be redrawn to be used again. They also make rain basins to collect water. They remember where the water sources are, and return to drink the water. These abilities help them because the desert is a dry place and water is very scarce. They obtain most of their water through the herbs, grasses, shrubs, new growth cacti, and the cactus flowers that they eat. All of these foods are found on the steep, rocky hillside slopes in Palo Verde and Saguaro Cactus communities where they live. In these communities, the main predators for desert tortoises are ravens. Tortoises protect themselves from ravens by drawing their head and legs into their hard, flat, pear-shaped shells. Although this is a good defense, it is not completely effective. The birds can still reach in the shell with their beaks and harm the tortoise. The tortoise population has declined ninety percent since the 1980's, and ravens cause fifty percent of juvenile tortoise deaths.

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

A typical Desert Tortoise environment © 2005 paloverde1

 

 Conclusion:

    It is extremely important that humans allow the desert tortoises to live their own lives, because humans as well as ravens are predators. These amazing animals have come so far and adapted in so many ways. The desert tortoise is a perfect example of a reptile that has impeccably adapted itself to its surroundings. It would be a terrible shame if they became extinct because of humans. There are many laws against touching, harming, and collecting tortoises. When coming across a desert tortoise it is important to not move it, unless it is in harm's way.  These actions can help save an incredible creature native to the beautiful Sonoran Desert.

Information on the Internet

References

"Tortoise." Encyclopedia Britannica. 15th ed. 2002.

Van Devender, Thomas. "The Sonoran Desert Tortoise: Natural History, Biology, and Conservation." Tucson: University of Arizona Press, August 2002

Learning Information

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