National Museum of Natural Science

Like most lizards, when mating, the male grass lizard bites onto the side of the female to keep the female in position, then inserts its hemipenes into the female’s cloaca. Pictured here is the mating behavior of the Hsuehshan grass lizard in the wild.

Reptile fact: The hemipenis is the male reproductive organ of lizards and snakes. There are two hemipenes, one each on the left and right side of the groin. They are usually stored inverted at the base of the tail. When needed for mating, they fill with blood and are everted from the cloaca.

Mating behavior