Night Lizards: Xantusiidae

People rarely see night lizards during the daytime, but they actually can be active both night and day, if the daytime temperatures are not too hot. Even on the best of days, however, they spend most of their time out of sight under dead leaves, inside plants, or in the cracks of rocks. They are much more likely to venture outside at night, when they may scramble about under the cover of darkness. Scientists still know very little about the behavior of night lizards.

Females of all night lizard species, except one, give birth to baby lizards. The typical litter holds five to eight babies. The Cuban night lizard is the only species in this family that lays eggs. The female lays a single egg at a time, dropping it into a hole. The egg hatches two months later.

In most lizard species, a female becomes pregnant only after she mates with a male. Some night lizards do not follow this rule, and the females can become pregnant on their own. Among female yellow-spotted night lizards, some mate with males to become pregnant, but others may not even see males. Some groups of yellow-spotted night lizards that live in Costa Rica and Panama are made up of only females. With no males in sight, the females are able to become pregnant themselves and have perfectly healthy babies.