|MadSci Network: Zoology|
This question is one which rarely supercedes the perenial query about age of certain tortoises. The Kenyan tortoise here may be a giant Aldabran tortoise, of which there are many in various zoos. This means we can age and check reproduction of males. However the prime directive for many zoologists is the production and care of the eggs. Females are therefore studied, along with their fertility. Poor old males are stimulated electrically and whether they would be able to produce sperm in the wild or not, active sperm apparently appear from these middle-aged individuals around 130. This brings us back to the reason for great age in certain animals. The big answer is that tortoises metabolise very slowly and can survive without oxygen for long periods. Each species must differ, especially if we compare the carnivorous aquatic examples with the traditional vegetarian land tortoise. In the end the only conclusion can be that a large enough tortoise cares little about age. "Lonely George", on the Galapagos island of Pinta survives without possibly ever having met a female in his maturity. The search for a possible mate from his own island or another island with almost matching DNA is fascinating. What seems little in doubt is whether his actual age is important in determining his virility. His sperm could be extracted by fair means or foul, if a mate turns up.
Try the links in the MadSci Library for more information on Zoology.