©David McChesney, outmywindows.com
Crunch, crackle. Crunch, crackle. What's going on under that creosote bush? Push aside the branches, peer into the shade, and you may catch a glimpse of the animal I observed while hiking in the park last spring: a desert tortoise, Gopherus agassizii, California's state reptile. Except in the steepest areas, these unhurried creatures make their home throughout the park, where they spend 95 percent of their time underground. Just how fast does a tortoise walk? (Answer at the end of this article).
Desert Tortoise Are Threatened
Perhaps because of the release into the wild of former pet tortoises during the past several decades, a deadly bacterial infection began to appear more and more frequently among wild tortoises. Upper Respiratory Tract Disease attacks the tortoise's respiratory system and can be transmitted through sharing of burrows, or through human handling of tortoises. This can occur when a person handles a sick tortoise and then unwittingly transmits the disease to a healthy animal.
Females generally behave less aggressively than males, and may spend more time underground since it is their task to nest and produce clutches of eggs. Females have, however, been observed aggressively defending their nests from the unwelcome presence of other reptiles and even park biologists! Tortoises may mate at any time of year, with the peak season from March through early October. A female may retain viable sperm for up to eight years after mating and still lay fertile eggs at that point. The average number of eggs per clutch is five, and they are usually laid from May through July. Several clutches may be laid annually, depending upon the availability of food and water. Eggs hatch anywhere from 70 to 120 days later. The chromosomes do not determine the sex of the offspring. Rather, the incubation temperature produces males or females.
It is illegal to remove a tortoise from the wild and bring it home as a pet. There are plenty of rescued tortoises looking for good homes. If you are interested in adopting one, please contact one of the park's visitor centers or a chapter of the California Turtle and Tortoise Club. Do not release pet tortoises into the wild; they may carry a number of diseases. Even if a domesticated tortoise appears healthy it probably will not be able to fend for itself after being dumped in the desert. It is used to being cared for, and may have lost its instincts to forage and protect itself from predators. Beyond that, tortoises are highly territorial and an intruder will not be tolerated for long. Tortoises have good vision and a good sense of smell, and they know their territory well. During its lifetime of 50 to 100 years, a wild tortoise rarely moves more than a couple of miles from its birthplace and is intimately familiar with the resources within its territory. These resources are vital to its survival, and may not support a new addition.
The aboriginal peoples who lived in the western deserts were well acquainted with the tortoise. Although not all groups would eat tortoise meat, it was generally prized for its food value. Some hunters lured tortoises onto the surface of the ground by placing a dish of water at the opening of a burrow. Tortoises were then roasted in cooking pits lined with hot rocks. The shells were put to a variety of uses: they served as bowls, scoops, spoons, ladles, and were sometimes ground into powder for medicinal purposes. They were also used to make ceremonial rattles: the carapace, or upper dome-shaped half of the shell, and the plastron, or flat underside of the shell, were joined together after being filled with small stones or seeds. The openings at either end were plugged with pitch. Tortoise motifs appear in desert rock art and in basketry and pottery. Several creation stories feature a tortoise shell, whose shape evokes the dome of the sky above the earth.
Biologists are currently studying the desert tortoise living within Joshua Tree National Park. Using measurements collected by such sophisticated equipment as radio telemetry and GPS (Global Positioning System), they are gathering information that allows us to increase our understanding of this threatened desert reptile.
Spring is a good time to spot a desert tortoise because the warm temperatures trigger an impulse to emerge from the burrow, forage, and look for mates. If you see one, please fill out a wildlife observation card, available at visitor centers and entrance stations. By slowing your pace, you will increase your chances of catching a glimpse into the unassuming world of the desert tortoise.
(Answer: average speed is 0.2 mph)
by Park Ranger Caryn Davidson
Did You Know?
Five of North America's 158 desert fan palm oases are located in Joshua Tree National Park, where fault lines force water to the surface. More...