You need to build a nesting box when the turtle is ready to lay eggs. You will need to know the nesting habits of your turtles. Different species have different nesting habits. For North American turtles such as sliders, map turtles, cooters, and box turtles (Terrapene), nesting usually occurs from late spring and early summer. You should think about building a nesting box around this time. You have to also watch out for signs that show that the turtle is gravid. Here are some of the signs that show that your turtle is gravid. - Expect the turtle to be restless. A gravid turtle will try to escape the enclosure. This is because she needs to find a suitable nesting site. She may try to climb out, dig through the bottom, and even swim through the glass. The turtle will usually start wandering and paddling frantically about the enclosure. - Expect the turtle to lose appetite. When a turtle is gravid, she may lose appetite and even stop eating. Also, some turtles may start eating more when they are gravid. Watch out for both signs.  The basking habits of the turtle may also change.  - The turtle will start digging with the hind legs. Turtles use their hind legs to dig holes for the eggs they lay. When the female turtle is gravid, she will try digging available substrate with the hind legs.