Are turtles nocturnal or diurnal? Do turtles sleep with their eyes open or closed?

In animal behaviour, nocturnality describes sleeping during daytime and being active at night. Many species which are otherwise diurnal exhibit some nocturnal behaviour; for example, many sea turtles attend breeding sites nocturnally to reduce the risk of predation (to themselves or their offspring) but are otherwise diurnal. In nature, green turtles (Chelonia mydas) can exhibit nocturnal activity in addition to their typically diurnal activity cycle.

Tortoises and terrapins usually sleep with their eyes closed. They would also prefer to sleep in some form of shelter, for example underneath a piece of driftwood. Some terrapins just “go to sleep” just like that, in any position they are in, some with their backs to the sky, some vertically (like holding on to another terrapin). Pancake tortoises, on the other hand, like to sleep latched laterally in between rocks.

If we look at the skeleton of a turtle, we will see that turtles have 5 phalanges, which essentially means that they have 5 “fingers”. However, physically, sea turtles’ limbs are called flippers, and tortoises and terrapins have legs. River terrapins have 4 front claws while painted terrapins have 5. Both have 5 hind claws though.