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SONORAN DESERT TORTOISE The Sonoran Desert Tortoise is flat and pear-shaped. It is active in summer and seek shade under large rocks and boulders. The tortoises tend to live on steep, rocky hillside slopes in Palo Verde and Saguaro Cactus communities. 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. Both sexes have a gular horn -- an anterior extension of the plastron (lower shell). The horn is longer in males and often upturned. Males use these in fighting with other males, attempting to insert the horn under the anterior edge of the carapace and by twisting to the side, flip the other male on its back. The opponent attempts to stand as high as possible to prevent this from happening. Mating may occur at any time that the tortoises are above ground; however, there seems to be more of this behavior in late summer and early. Females store sperm and egg laying occurs May, June and July. The number of eggs varies. Female size seems to be one factor. A mature female might lay 4-8 white, hard-shelled eggs in a clutch and produce 2, sometimes 3 clutches in a season. Only a few eggs out of every hundred actually make it to adulthood. Desert Tortoises don't reach sexual maturity for 15 to 20 years. Much of the tortoise's water intake comes from moisture in the grasses and wildflowers they consume in the spring. During very dry times they may give off waste as a white paste rather than a watery urine. Adult tortoises may survive a year or more without access to water. Tortoise´s eat herbs, grasses, some shrubs and the new growth of cacti and their flowers comprise a major portion of the diet. If there is little summer rain, tortoises will utilize dry forage. |