Cold-blooded creatures
     Like other reptiles, turtles are cold-blooded, which means that their body temperature depends upon their environment.  On cold days turtles must find a place to keep warm.  On hot days, turtles often bury themselves under leaves or in the mud to stay cool.

Turtles can remain under water a long time
     This is partly due to the ability of some turtles to absorb oxygen from the water not unlike a fish does with its gills (though turtles do not have gills!).  Turtles can also slow down their heart rate and remain inactive underwater for long periods of time, requiring less oxygen and surviving off energy stored in their body.

Only a few survive
     A young turtle is not safe until it grows larger and its shell becomes hard enough to protect it from most of its enemies.  Only a very small number of baby turtles survive to become adults.