Desert night lizard

Originally published in The Manitoban, October 20, 2010

I'm tired. I'm getting sick, I have exams coming up, papers due, grant applications to write, I had to cook my own Thanksgiving dinner, and I just want to curl up on the couch until January. Sound familiar? Well anyway, I read this great article about whale poop and my friend told me about Pacific barreleye fishes and I felt a lot better. The sun is still shining, after all. We've got until at least December 2012 and I am not going to write about whales or barreleyes just yet. I am going to write about lizards instead.

The desert night lizard, Xantusia vigilis, lives in the Mojave Desert, which occupies portions of California, Nevada, Utah and Arizona, and spends a lot of its time hiding under logs. They feed on invertebrates such as caterpillars, moths, termites, ants and beetles and are what is referred to as a 'sit and wait' predator—they don't hunt actively but tend to remain in hiding and then pounce on their unsuspecting prey when it comes near their hide out. 

They are viviparous (“live-bearing”), and females give birth to an average of two young per year. They are small, measuring between 1.5 and 2.75 inches long, not including the tail; which, when threatened, is very likely to break off and wiggle around as a distraction so the lizard can escape from potential predators. I wonder what would be the best appendage for humans to lose when confronted by late-night muggers or street gangs of ten-year-olds? Perhaps the wallet hand? I see potential for esoteric stem cell research grants...

So far the most interesting thing I've learned about the desert night lizard pertains to its complex social structure. A graduate student at UC Santa Cruz named Alison Davis, now a post-doctoral researcher at UC Berkeley, led a five-year study of the lizards and found out a bunch of really cool stuff. 

Unlike many lizard species, X. vigilis live in groups, often hanging out under the same log for years on end. Young lizards remain with their parents and siblings for several years. Genetic testing using DNA microsatellite markers confirmed that separate aggregations of the lizards were composed of related family groups, the largest so far tested being a group of 13 members. For the less genetically savvy, microsatellites are short segments of DNA that have a repeating sequence of base pairs (CACACA for example). These segments can be passed on from parents to offspring and eventually, populations will retain a characteristic set of microsatellites distinct from those of other populations.

Aside from the fact that most lizard species are solitary, the sociality of the desert night lizard may provide future insights into the evolution of more complex social behaviours, like those seen in primates (including humans). 

There are only about twenty known species of lizards that live in family groups and of these, only two give birth to live young, implying that viviparity may be critical for the evolution of cooperative behaviour in animals. Insight into the social interactions of reptiles such as the desert lizard can provide valuable information about the evolution of kin-based groups and cooperative behaviour across a wide variety of taxa, including birds and mammals, and may help provide a means of reliably predicting other species that might be predisposed toward complex social and group behaviours. Such information could provide insight into our own evolutionary past and reveal a common evolutionary ground for social and family interactions throughout the animal kingdom. Neat!

Desert lizards don't have eyelids.