Stripy, Slithery, Splendid: European Glass Lizard Hatchlings | Smithsonian's National Zoo - Smithsonian's National Zoo and Conservation Biology Institute

Because glass lizards don't have arms, legs or hands, a male holds on to a female by placing his mouth on her neck and biting down. Potentially, he could injure her in doing so, but for the most part the marks he leaves are superficial. Once she sheds her skin, they are all gone.

Glass lizards are solitary in the wild, but they can be found together during breeding season. Robin introduced them when their behaviors indicated they we ready. Instead of removing the male quickly—as she had done in years past—she kept them together for an extended period.

Our team observed them closely every day for any behavioral changes. They also checked the female's neck for any bite marks—a sure sign of a breeding attempt. Once Robin saw the marks, she removed the male and gave the female some alone time. If she did not lay eggs, Robin brought the male back to try again.

During our rounds April 28, we saw that the female dug a nest in the soil and was wrapped around two soft and leathery eggs, guarding them. She picked a good spot—the male's preferred hideaway, too—but she would not let him come near it. Male glass lizards do not play a role in incubating or raising the offspring, so the female was not willing to share her space. We placed him back in his bachelor pad.

Glass lizard eggs are about the size of a ping pong ball, but their shape is more oval than round. Because this female laid infertile eggs for the past two years, our first step was to candle them (shine a light into the egg) and look for signs of embryonic development, such as blood vessels. To our delight, that's exactly what we saw!