Figure 13.29: A Galapagos giant tortoise, pictured here, can grow to over 4 ft in length and
weigh about 670 lb. ( 18 )
Most turtles that spend most of their life on land have their eyes looking down at objects
in front of them. Some aquatic turtles, such as snapping turtles and soft-shelled turtles,
have eyes closer to the top of the head. These species of turtles can hide from predators
in shallow water where they lie entirely submerged except for their eyes and nostrils. Sea
turtles (Figure13.30) possess glands near their eyes that produce salty tears that rid their
body of excess salt taken in from the water they drink.
Figure 13.30: A species of sea turtle, showing placement of eyes, shell shape, and flippers.
( 22 )
Turtles are thought to have exceptional night vision due to the unusually large number of
rod cells in their retinas. Turtles have color vision with a wealth of cone subtypes with