The turtle lives ‘twixt’ plated decks
Which practically conceal its sex?
I think it’s clever of the turtle
In such a fix to be so fertile
The poet Ogden Nash was right about the turtle’s external ambiguity and fertility, according to Grzimek’s Animal Encyclopedia (Van No strand Reinhold). Turtles are not only enthusiastic breeders; they also have external sexual characteristics that often make it hard for creatures other than turtles to determine which is which. The male is sometimes distinguishable by an indentation or curvature in its plastron, or lower shell, which fits over the back of the female; females have a flat or convex plastron.
To fertilize female’s eggs, the male turtle conceals a sexual organ inside the cloaca, or waste removal chamber. The male positions itself over the female and often grasps the upper shell, or carapace, with its claws, then curves its tail until the vent contacts the female’s vent; the penis emerges for often fertilization. The often dozens of eggs develop internally and are then usually laid and buried in sandy soil.
Fertilization is sometimes preceded by elaborate courtship rituals, with hours of demonstration followed by a few minutes of copulation. The female can store sperm to fertilize its eggs, sometimes years later.