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.