Abstract
Reptiles have very flexible growth rates, depending on living conditions - in particular dietary resources. Here, I demonstrate a difference in the growth rates of captive specimens, as compared to literature data for free-ranging ones, in Leopard tortoises (Geochelone pardalis), African spurred tortoises (G. sulcata), Hermann’s tortoises (Testudo hermanni) and Spur-thighed tortoises (T. graeca). Such high growth rates are traditionally thought to be linked to health problems. In the case of the G. sulcata dataset (spanning 18 years for the captive individuals), it could be shown that fast growth leads to a fast reproductive maturity, as expected from inflexion points of growth curves. In a retrospective evaluation of 539 tortoise patients of the University of Zurich, no evidence for diet- or growth-related disease risk was found in animals that were particularly heavy for their age. However, typical diet- or growth-related disorders were more frequent among younger patients, suggesting that animals with such problems do not often survive to older age. Raising tortoises on intensive feeding regimes in captivity may considerably shorten generation times during the breeding stage of restocking programmes. Whether fast growth presents a health risk needs to be evaluated in controlled studies. The observations also suggest that feeding regimes in captivity – even of appropriate diets - should be restricted if replication of conditions in the wild is a husbandry objective.
Ritz, Julia