Tuleyome's Science Corner - Western Fence Lizards

Kristie Ehrhardt • May 24, 2023

Western Fence Lizard (Sceloporus occidentalis)

The Western Fence Lizard (Sceloporus occidentalis) is a moderately sized lizard commonly found throughout the western United States from Eastern and Southwestern Oregon, Southwestern Idaho, Nevada, Western Utah, Arizona and Baja California from sea level to around 11,000 feet. They can be found in a variety of habitats within their range including woodlands, grasslands, chaparral, forests, and urban areas such as farmland and neighborhoods. They usually occur near water and do not occupy desert regions.


Lizards are commonly measured from snout to vent (STV) and Western Fence Lizards usually range from a little over two inches to about three and a half inches STV. This measurement does not include the tail as is common when measuring lizards because tail length of individuals can vary greatly. Coloration ranges from light to darker brown, gray or even jet black but it is believed that the color variation is less camouflage and more related to thermoregulation, the process that helps them maintain their core internal temperature. Because lizards are ectotherms (cold blooded), their body temperature depends on external heat sources such as sunlight itself or the surfaces of other things that are warm such as rocks or the ground. Western Fence Lizards are diurnal which means that they are active during the day and can often be seen in open, sunny areas basking in the sun on rocks, fallen trees, trail edges or fences. Because they like to bask in open areas, they are susceptible to predation and a cold lizard is a slow lizard - an easy snack for keen-sighted raptors and mammals.


They have sharp claws for climbing and their sharply pointed scales make them appear spiny. They have grayish stripes along the length of their body with a lighter sandy colored wave pattern going horizontally. You might have grown up calling Western Fence Lizards “blue bellies” for obvious reasons; the adult males have bright, blue bellies as well as blue patches on the underside of their necks. The blue is usually absent or very pale on females and juveniles which makes determining sex in adult lizards fairly easy. The shade of blue can range from almost shockingly blue to a lighter, pale blue. The undersides of the front and rear legs are yellow to orange and occasionally, lighter individuals can have some bright, iridescent turquoise blue scales on their backs. Males establish territories which usually includes higher areas where they can perch and keep an eye out for intruders. You may have seen them busting out a few pushups to threaten rival males (or maybe just a passerby) to keep them from their territory and they will engage in physical combat if the rival male does not heed the warning to stay away. Adult males also do pushups and bob their heads to show off their bright blue patches to impress females. Courtship and mating usually occur from March through July and females can lay up to three clutches of up to nearly 20 eggs. The eggs are laid in shallow depressions dug by the female in loose, moist soil and begin hatching in August. Keep an eye out around that time and you will probably start seeing teeny tiny little two-inch baby Western Fence Lizards scurrying for the nearest safe place. Most of them do not breed until their second spring and individuals can live from five to seven years in the wild if things go well for them.


Western Fence Lizards eat a variety of invertebrates such as spiders, caterpillars, crickets, grasshoppers, mosquitoes and sometimes even their own babies.


If their tail is nabbed by a predator, they can detach it in an attempt to escape. The discarded tail continues to wiggle which will hopefully distract the predator enough so the lizard can escape. The tail usually grows back in about a month but is almost always shorter and will have a different scale pattern. Although this may save the lizard’s life, it is very costly and stressful for them.


It’s been discovered that Western Fence Lizards have an immunity to Lyme disease. They have a protein in their blood that kills the bacteria that causes Lyme disease. When ticks carrying the bacteria feed on a Western Fence Lizard, the protein kills the bacteria in the tick’s gut and the tick can no longer spread the disease. It’s been shown that cases of Lyme disease are fewer in areas occupied by Western Fence Lizards. Pretty cool.


-Kristie Ehrhardt (kehrhardt@tuleyome.org)


Tuleyome Land Conservation Program Manager

RECENT ARTICLES

By Ellen Jenkins July 2, 2026
From left to right, Horticulture Interns Ellen Jenkins, Rithika Warrier, and Diego Barraza Hernandez, with Education Associate Geoff Benn, who coordinates the internship program. From September to June, I worked as a Horticultural Intern at Tuleyome. Each week at the Woodland Regional Park Preserve, I would meet with my mentor Teri Barry. Over the course of the year, we worked together identifying, documenting, and analyzing the preserve's growth. Through this opportunity, I gained experience in hands-on restoration efforts, familiarity with plant taxonomy and classification, and community outreach.
By Kristie Ehrhardt July 2, 2026
I’m sure you already know that the Bald Eagle is used as a symbol of our Nation’s freedom, strength, perseverance and independence. It is said that our founding fathers chose the Bald Eagle to adorn our Great Seal because it is indigenous to North America and if you look closely at it, you’ll see that it is holding 13 arrows and an olive branch simultaneously symbolizing the power of war and the power of peace. But, what about our national mammal? Er, maybe you didn’t even realize that we had a national mammal… President Barack Obama designated the American Bison as our national mammal in May of 2016. It too is endemic to North America and in prehistoric times, millions of them roamed through roughly two-thirds of the United States. Their range was known as the “great bison belt” - a stretch of habitat that encompassed the forests of Alaska, the grasslands of the North American plains and stretched from the Great Basin east to the eastern Appalachian Mountains. Side note - I’m just gonna come clean right now and tell you that the historic range of the American bison, American Buffalo or just plain bison or buffalo does NOT include the Berryessa Snow Mountain National Monument (Monument). I’m supposed to be writing about the Monument region and I picked a topic that is clearly not there but it’s important and they are impressive so please don’t tattle. Another side note - the American Bison and the American Buffalo are one in the same and both names can be used interchangeably. Its scientific name (genus and species) is actually Bison bison so I guess calling them bison is probably more scientifically accurate but either works. Bison are North America’s largest land animal; an adult male averages about 2,000 pounds - that’s a ton (thanks Schoolhouse Rock, I will never forget this one!), are about 12 feet long from nose to rump and about six feet tall. Females max out at around 1,000 pounds and are a little over nine feet long. In the wild bison can live ten to twenty years. Both females and males have massive forequarters and sport what looks like a shaggy, long-sleeved sweater. Both sexes have short, curved horns that are an integral part of their status in the herd and defensive strategy. During the snowy winters, bison display a dark brown winter coat and in the summer they show off their lighter brown summer-bods. Calves typically arrive from March through May depending on weather conditions. When they’re first born calves are an orangey-red color which earned them the nickname “red dogs”. Within a few months they become darker brown like their parents and their little horns start to poke through. Around this time they also begin to develop their iconic shoulder hump. The hump is made of solid muscle buttressed by elongated vertebrae. This dense network of muscles act as a powerhouse that allows the animal to swing its massive head from side to side and plow through icy snow to access buried forage enabling them to survive even the harshest winters. Although they are not known for keen eyesight, bison have superb senses of hearing and smell. As monumental (get it?) as these animals are, they are shockingly quick and agile. Bison have been clocked at running 35 miles per hour (!), they can spin and turn on a dime, leap over high fences and are incredibly adept swimmers. All these mad skills on a strictly vegetarian diet - that’s ruminant efficiency. For thousands of years, before the European settlers arrived, Native Americans of all tribes and regions revered the bison. They were the cultural, spiritual and resource backbone of indigenous societies across the United States. Every part of the animal was used; the meat was consumed, the hide was used for clothing, shoes and shelters, and the bones and hooves were used for tools and weapons. Even the sinew was used for sewing and bow strings. Everything was copacetic then came the Europeans with their domestic cattle diseases and thoughtless greed. Bison were hunted to near extinction within roughly just 100 years. Their numbers went from an estimated 60 million (!) to less than 550 individual animals by 1889. They were hunted mercilessly and their habitat destroyed, some say as a way to control the Native Americans by removing their primary resource. One of the buffalo’s biggest fans was President Teddy Roosevelt. In the early 1880’s he traveled to what is now North Dakota (shout out to my people!) to hunt. After recognizing the bison’s diminishing population numbers he co-founded the American Bison Society in 1905 to help conserve and protect this American emblem. For many years the few buffalo that remained were only found in national parks and preserves but primarily on Native American reservations. Had it not been for the willingness of tribes across the country to work with interested individuals and state and federal governments, the American Bison would be gone today. Much like the Bald Eagle, the bison is an authentic symbol of American character and as it turns out, another one of the greatest conservation success stories in U.S. history. The bison within the Yellowstone National Park boundaries are direct descendants of the original animals that roamed our country’s grasslands and are the only herd that still occupy their original prehistoric location. This free-ranging herd numbers approximately 5,500 animals and is the largest herd on public land. Recovery efforts paid off and today bison can be found in all 50 states including private and tribal lands, national parks and wildlife refuges.