First, release of captive tortoises is a violation of the Federal Endangered Species Act under the section on "take", which includes capturing, pursuing, shooting, harming and harassing. Released pets are likely to have harmful effects on the wild populations. Pet tortoises often carry diseases and parasites which may not be apparent with casual inspections. These diseases can and already have infected wild populations. A prime example is the appearance of the highly contagious and usually fatal Upper Respiratory Tract Disease at the Desert Tortoise Research Natural Area and elsewhere in the Mojave Desert in the late 1980s. This disease, which is caused by very small bacteria called Mycoplasma, is killing thousands of wild tortoises. Experts think that Mycoplasma may be transmitted to wild populations by unauthorized releases of ill captive tortoises.

 

Second, recent research indicates that several genetically distinct tortoise populations exist. A tortoise from one genetically distinct unit should not be mixed with tortoise populations from another genetic unit. Often the pet owner does not know the source of the captive tortoise.

 

Third, some studies indicate that domesticated tortoises do not have a high survival rate, probably because they have forgotten the intricate details of living in the harsh desert environment. Pets do not dig burrows as readily or as well as wild tortoises. Pets also may not remember how to forage.

 

Fourth, release of captive tortoises increases competition and stress for the existing wild tortoises. Wild tortoise populations are already threatened with loss and deterioration of habitat. The amount of undisturbed desert decreases yearly, usurped by construction, development, and other human pressures. The quality of remaining habitat is also decreasing because of the many demands for land use: mining, grazing, off-road vehicle recreation, and energy development. Deserts recover very slowly from disturbance. As a result, habitats support progressively fewer tortoises.

 

Fifth, released pets can harm wild tortoises by interfering with the social structure. Wild tortoises have well-defined activity areas and often defend territories and burrows. The introduction of new tortoises to an area can stimulate competition for burrows, food, and other resources.