The yellow-bellied three-toed skink lays its eggs along the coast of southeastern Australia. The yellow-bellied three-toed skink gives birth to live young in the mountains of Australia. Same species — two different ways of reproducing. What's going on here?


Along the warmth of the coast, this long, spindly-legged lizard deposits its eggs where they can fend for themselves. If a predator doesn't get them, they'll hatch into a whole new generation of yellow-bellied skinks. Up in the mountains, the eggs would have a rougher time of it. The temperature at higher altitudes drops, and the skink eggs don't have the same chance as their coastal siblings do. The yellow-bellied skink has found a solution to that; it disposes with eggs entirely and carries its young internally until it can give birth to them.

There are two other reptile species that both give birth and lay eggs. Researchers believe that they, like this skink, are in the middle of a jump. In time, they may stop laying eggs entirely, joining the twenty percent of snake and lizard species which give birth to live young.


Find out more at National Geographic.

Photo: Rebecca A. Pyles