Walking home from school yesterday, Rachel and I stumbled upon an alligator lizard sunning herself on the trail. Her eyes were fiery orange, and her back was colored like indian corn. She held her legs close against her sides. Possibly she had been undulating like a snake through the adjacent field, as alligator lizards are known to do. I say she because this individual had a slender head; male alligator lizards possess massive jaw muscles, giving their heads a triangular shape.
Two species of alligator lizards can be found in Santa Cruz: the northern (Elgaria coerulea) and the southern (E. multicarinata). Though similar in many respects, the northern and southern alligator lizards differ in their reproductive strategies. Southerners, like many other reptiles, are egg-layers, but northerners are viviparous, meaning that they give birth to live young.
Vivipary crops up here and there throughout the lizard family tree. One reasonable explanation for the difference between Santa Cruz’s two alligator lizards is that the northern species commonly experiences colder temperatures and shorter summers than the southern species. Rather than deposit her eggs in a spot that might be too cold for them to hatch, a northern female might be better off keeping her eggs inside her body and seeking out sunlight in which to bask and regulate the temperature of her progeny. A southern female, in contrast, can lay her eggs in a warm burrow and get on with her business.
*For a good comparison of northern and southern alligator lizard field marks, check out californiaherps.com. You can also look at the Natural History of the UC Santa Cruz Campus for more detailed information about their reproductive habits.