The 'western fence lizard', 'swift', or 'blue bellied lizard' - sceloporus occidentalis - is a medium-sized (up to about eight inches including tail), mottled lizard that ranges from Washington state to Baja California, and as far east as Utah. It doesn't live in the harsh deserts, but it is found from the coast up to nearly 6,000 foot elevations, from the scrubbiest coastal chaparral to mountain forests.

It has a habit of sunning itself on high points such as rock outcroppings or fenceposts (hence the name 'fence lizard'), which makes it a fine target for hawks and other predators in its habitat. This bold and careless lifestyle has required it to develop lightning reflexes and quick-burst speed (hence the name 'swift').

Another of its defenses is the ability to change colors according to its surroundings. Like many other lizards, it can lighten or darken its coloration to match the background, but it will sometimes adopt a contrasting hue. Perhaps this mimicks a dappling of shadow, or maybe the little beast simply enjoys challenging fate. I admit the second interpretation because its underside reveals a suppressed flamboyance in its nature. Its ventral coloration is characterized by gaudy patches of blue or turquoise (hence the name 'blue-belly'). These are most pronounced in the males, and, as you might expect, become much brighter during the mating ritual.

It is a pleasant and inoffensive creature, dining mostly on insects, and in turn providing a good food source for larger predators. Successful over a wide range of habitats, it is in no way endangered. If all that were not life-affirming enough, its presence in an area reduces the incidence of ticks carrying Lyme disease from about 50% to about 5%. It seems that ticks who feed on the blood of the blue bellied lizard are unharmed, but the Lyme disease spirochetes that they harbor are destroyed.

Kingdom Animalia 
Phylum Chordata 
Class Reptilia 
Suborder Squamata 
Family Phrynosomatidae 
Genus Sceloporus 
Species S. occidentalis

On any cold morning in the Western United States, go outside and look for blue bellied lizards.

You'll find them under rocks, under lumber, any place that has shelter. Once you've found one, pick it up. If you got to it early enough, it'll be too cold to move much.

The lizard's scales are spiny — gently run your finger along them the wrong way. They're like sandpaper. Now go the right way: like silk. Its skin is paper thin. Most people are too afraid of reptiles to realize they're some of the softest and most delicate creatures around. You may as well be handling gossamer.

Break down "ectotherm": outside temperature. Reptiles are ectotherms. This means they take warmth from the environment rather than generate it from within. But "environment" is really too broad a term. They take their warmth from the sun. Normally, this being would muster the strength to stick its face out in the light and let its blood carry the warmth throughout its body. Reptiles practice the crudest form of thermoregulation.

Now you're going to do something cool.

Cup the lizard in your hands, covering it with your skin. Gradually, you'll feel its lungs expanding and contracting. It will start to move. Your hands expel a lot of heat. The mitochondria in your body produce warmth; normally it dispels in the air.

After a few minutes, open up your hands and give the lizard a little rub on the belly. It may take a few seconds for the animal to snap out of the ecstacy of your heat bath. When you picked it up it was stiff as a board: now it's a clump of muscles and claws, streaking in whichever direction is Away.

For a few moments you were someone's sun. Warmth comes from the sun and your hands.

The taxonomy of the western fence lizard is currently a bit jumbled. Until recently, some six different species were classified. But recent molecular systematics work suggests that there are four clades and eleven genetically separate subspecies. They're distributed throughout the western US, where slight variations in environment, climate, ambient critters etc. justify the assumption that evolution has done a bit of separation and refinement.

These aren't big lizards. Without tail, they get four inches long — around the length of your middle finger. The alternate name "blue bellied lizard" comes from the iridescent blue patches males carry on the sides of the belly and on the throat, which are used as territorial and mating displays. Because females and juveniles have little use for such gaudiness, their patches are much less pronounced.

While blue bellied lizards are associated with desert life, they aren't actually found in the desert. They settle in the scrub and chaparral of the semi-desert, climbing as high as 2000 meters. The heart of their range is California, but they're found up into Utah and down into Baja California, and on the small islands dotting the Pacific near the North American west coast. In higher elevations they take up residence in the forests, sunning themselves where light falls through the canopies.

Like most lizards, blue bellies can alter their color slightly to match surroundings. Put a light lizard on a dark rock; it turns dark. Interestingly, they tend to stay dark when on light surfaces, appearing as shadows.

The blue belly is carnivorous, subsisting on ants and other insects. Its tendency to take up position in high places makes it easy prey for hawks, but it compensates for the devil-may-care attitude with lightning fast reflexes. When confronted without an escape route, males will perform jerky 'push-ups' to display the blue patches and upper body strength.

Mating season is May through June. Eggs are distributed ten or so per clutch in July and hatch as early as mid-August. As hatchlings go, blue bellies are quite large — counting tail, they're about two inches long.


You can make pets of lots of things.

Like most reptiles, blue bellied lizards are pretty low-maintenance pets. And since they're crawling around on the rocks by the dozens, they're pretty easy to catch — especially early in the morning.

You'll want a five to ten gallon tank, depending on the number and size of lizards. Since these guys are climbers, you'll want to include some driftwood and rocks for recreation. Soil makes a good substrate; some folks use paper towels for easy maintenance, but it isn't nearly as attractive. Keep lighting simple — a sixty-watter should do the trick if ambient temperatures aren't warm enough. Spotlights will cause burns. Clean the tank every two to three weeks, washing driftwood and other playground items with warm water and mild soap. Males are territorial, so don't house them together. Provide water in a small, shallow vessel. A dip platter works nicely.

Feed it any small, non-threatening bug you can catch. If you're squeamish about catching bugs, you can buy crickets at any reptile supply store. If you've got a small lizard start it out on ants and work it up to larger vermin as it grows. Feed it in intervals of two or three days up to a week. Reptiles are slow eaters.

Every now and then let it fall asleep in your hands. Lizards love warmth.


San Diego Natural History Museum

Reptic Zone

Las Pilitas



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