Otherwise, the overlap among authors in the two categories of turtles was low, virtually zero. During the next decade and into this one, the situation has changed in two ways. Second, many of the authors of freshwater turtle papers were formerly authors of sea turtle papers. This is a healthy sign, for all of the species under study are turtles and are more similar to each other than they are to any other group of organisms. The same basic biological principles apply.
All turtles lay eggs and begin life as vulnerable prey items for a vast array of predators.
Most develop self-protection through large size and body armor. Perhaps the greatest similarity between marine and freshwater turtles is the documented longevity of individuals, which exceeds that of almost all other animals. Therefore, they should be studied as a group for many aspects of their biology, although different questions may be asked relative to certain physiological questions influenced by salinity levels. Or, certain ecological questions may need to be approached differently, such as ones involving the immense ocean distances traveled by some of the sea turtles compared to overland travel by freshwater species. Also, most turtles face innumerable human-caused perils, some that are similar and some that differ depending on whether the turtle lives in the ocean, in fresh water, or on land.