Patterns of survivorship in turtles (order Testudines)

Survivorship data by general age-class are reviewed for 30 species of turtles representing nine families. Survivorship varies significantly across age-classes, with mortality generally inversely related to age (type III survivorship). Survivorship also varies significantly across habitat types, with marine and terrestrial turtles exhibiting higher survivorship early in life than freshwater turtles. Marine turtles also tend to have the lowest survivorship as adults. The implications of these findings for the evolution of marine and terrestrial turtles form ancestral freshwater forms are discussed.