Aging Desert Tortoises

                    ----------------------



The age of young desert tortoises can be estimated by their size

and rate of growth, though the high-protein diets frequently fed

to captive tortoises can result in freakish overgrowth and

development.  Counting scute rings is meaningless.  Plastron

(bottom shell) differentiation usually occurs at 10-15 years of

age, and maturity is reached at 25-30 years of age.  Once a

desert tortoise has reached maturity, it is virtually impossible

to determine its exact age.  However, shell patterns change and

the shell becomes flattened and concave as a tortoise ages.  As a

result, experienced biologists can "guestimate" the age of an

older tortoise with reasonable accuracy.  Tortoises theoretically

grow for life, and giants are occasionally found.  The life span

of desert tortoises is thought to exceed 130-150 years!