ANIMALS IN DESERTS

Desert tortoises spend much of their lives in burrows, emerging to feed and mate during late winter and early spring. They typically remain active through the spring, and sometimes emerge again after summer storms. During these activity periods, desert tortoises eat a wide variety of herbaceous vegetation, particularly grasses and the flowers of annual plants (Berry 1974, Luckenbach 1982). 

Desert tortoises are essentially "K-strategists" (MacArthur and Wilson 1967), with delayed maturity and long life. Eggs and hatchlings are quite vulnerable, and pre-reproductive adult mortality averages 98% (Wilbur and Morin 1988, Turner et al. 1987, Morafka in press). Adults, however, are well protected against most predators (other than humans) and other environmental hazards and consequently are long-lived (Germano 1992, Turner et al. 1987). Their longevity helps compensate for their variable annual reproductive success, which is correlated with environmental conditions.

Source: http://refuges.fws.gov/NWRSFiles/WildlifeMgmt/SpeciesAccounts/Reptiles/DesertTortoise.html

 

 

 

Source:http://pub4.ca.blm.gov/caso/wf-destor.html

 Desert tortoises are well adapted to living in a highly variable and often harsh environment. In adverse conditions they retreat to burrows or caves, at which time they reduce their metabolism and loss of water and consume very little food. Adult desert tortoises lose water at such a slow rate that they can survive for more than a year without access to free water of any kind.

During a recent drought, desert tortoises at a study site in eastern California not only survived with very little food or water, but they produced an average of three eggs per female per year (B. Henen, UCLA, pers. comm.). Desert tortoises apparently tolerate large imbalances in their water and energy budgets (Nagy and Medica 1986). This ability enables them to survive lean years and exploit resources that are only periodically available.

During years of average or better than average precipitation and forage production, desert tortoises can balance their water budgets and have a positive energy balance, providing opportunity for growth and reproduction (Nagy and Medica 1986). All the mechanisms by which desert tortoises maintain their energy and water balance in the face of stochastic availability of resources are still not clear, but desert tortoises seem to be flexible in their mechanisms of energy and water gain and in their expenditures of these resources (Wallis et al., 1992).

Source: http://refuges.fws.gov/NWRSFiles/WildlifeMgmt/SpeciesAccounts/Reptiles/DesertTortoise.html

 

 

 

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