Causes of Mortality and Diseases in Tortoises

Most of the 40 species of tortoises are experiencing population declines. Of the various causes of mortality in wild populations of tortoises, the interactions of disease and population dynamics are least understood. Although habitat degradation is considered the most significant threat to wild populations of tortoises, disease is being observed more frequently in certain popu lations. An upper respiratory tract disease has been seen in populations of desert tortoise, Gopherus agassizi, in the Mojave Desert, USA, and certain populations of the gopher tortoise, Gopherus polyphemus, in Florida, USA. Much more information is available on diseases of captive tortoises than on those of wild tortoises. Of infectious diseases, viral, bacterial, mycotic, and parasitic diseases have all been reported. Noninfectious diseases identified in tortoises include various nutritional diseases, hypothyroidism, and neoplasia. Virtually nothing is known about the effects of pollutants/ toxicants in individual or populations of tortoises.