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Blunt-nosed leopard lizards (Gambelia sila) might just be the most mind-boggling creatures inhabiting the Diablo Range. It’s not merely because leopard lizards are desert creatures—the Diablo Range houses an array of desert fauna, including several other lizard species. Neither is it solely because they prefer flat, open areas—so do kit foxes. It’s both of those reasons, along with rarity. Blunt-nosed leopard lizards are not only protected under the Endangered Species Act, they’re among the first species granted protection, alongside such well-known brethren as California condors and grizzly bears.

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The saga of the blunt-nosed leopard lizard stretches back perhaps 10 million years, when uplift along the Garlock Fault resulted in the rise of the Tehachapi Mountains, forming a barrier between the San Joaquin Valley and the Mojave Desert. Some species that once existed in both areas became separated, and over time isolation led to the evolution of taxa such as the San Joaquin antelope squirrel, San Joaquin coachwhip, and San Joaquin kit fox. The leopard lizards on the San Joaquin Valley side diverged from their Mojave Desert ancestors, their most noticeable adaptation being a truncated snout. They became blunt-nosed leopard lizards, found along the west side of the San Joaquin Valley and surrounding foothills and nowhere else.

Blunt-nosed leopard lizards are large, earth-toned lizards with considerable variation in pattern. Some feature a series of cream-colored lines across the back, while dark blotches reminiscent of leopard spots may be prominent, subdued, or practically nonexistent. During breeding season adults become considerably flashier: males take on a gorgeous background color similar to cantaloupe flesh, while females exhibit eye-catching splashes of red along their sides. From snout to tail tip, a large adult may measure 15 inches in length. That’s one impressive lizard.

And if breeding color and size aren’t enough, their speed is another marvel. Most lizards scamper a few feet, but leopard lizards can sprint a number of yards, occasionally on two legs. That’s a sight to behold. They run not only to avoid threats, but to capture prey, primarily insects and arthropods. Grasshoppers are a frequent menu item, and they’ll take larger prey as well—other lizards, including young of their own kind.

Blunt-nosed leopard lizards do best on open ground with scattered shrubs, which they depend on for shade and as refuge. They rely heavily on burrows dug by mammals such as kangaroo rats and ground squirrels. They’ll make use of the raised earth entrances as promontories, where they can scan the surroundings for both prey and predators, and bask in the sun. The adjacent burrows function not only as hiding places but as refuges from the weather, places to wait out chilly, windy weather and the blazing heat of summer. Like many lizards, blunt-nosed leopard lizards have a preferred temperature range for being active above ground, generally between 75 to 100 degrees.

While some lizards are active throughout the year, blunt-nosed leopard lizards are active for only a portion of the calendar. Adults emerge from winter burrows in spring and return by late summer, staying active just long enough to breed and eat enough to fast the rest of the year; no sense exposing themselves to predators any longer than they have to. Hatchlings operate on a different time scale—they emerge in summer, about the time when the adults are retreating underground for the year. Given the threat of cannibalization, that’s a good thing. Hatchlings feed and grow throughout the summer, and sometime in fall take refuge underground like their elders, emerging the following spring.

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Blunt-nosed leopard lizards originally inhabited millions of acres of the San Joaquin Desert, as well as the intermountain valleys nearby, such as the Carrizo Plain. They ranged at least as far north as Stanislaus County, and there’s a highly credible record of one spotted near Corral Hollow as recently as 1960. Today, it’s doubtful that any persist north of the Panoche region. Throughout their range, blunt-nosed leopard lizards have been decimated by habitat loss, as land has been converted from desert to farmland, oil fields and solar energy projects, and as cities and towns have sprung up over what was once prime habitat. Some lizards—fence lizards, alligator lizards—can thrive among orchards and in suburbs, but not leopard lizards; trees are as foreign to them as seaweed. They also have large spatial requirements; an adult male can roam a territory spanning dozens of acres. That’s a lot of ground, and it needs to be unbroken.

Habitat loss can also be subtle. There are hundreds of thousands of acres along the east flank of the Diablo Range that persist as open space, but despite the lack of development, the leopard lizards are gone. That absence might be due to the proliferation of non-native grasses. Wild oats and brome have replaced the native forbs and bunch grasses, and that did the lizards no favors. Non-native grasses grow thick and tall, creating a forest that lizards can’t see beyond nor run through. They can neither forage nor flee. Where leopard lizards and grasslands coexist, it’s in places where grass growth is meager.

Another likely factor in the decline has been the use of pesticides and rodenticides. The west side of the San Joaquin Valley has seen multiple campaigns against various insect pests using widespread aerial spraying. Those efforts both poisoned and reduced the food supply for lizards. The equally enthusiastic war on rodents may also have contributed to the lizards’ downfall by eliminating the creatures that dig the burrows lizards rely on for shelter and refuge. Given the spread of invasive grasses and aggressive pest-control efforts, all that open space mattered little, for lizards disappeared.

Today, the stronghold for the species are the natural lands west of Bakersfield—the Elk Hills and Carrizo Plain. Scattered populations persist on the floor of the San Joaquin Valley in places such as Pixley National Wildlife Refuge, but those populations are small and isolated. Besides a population outside of Madera, the lizards in the Panoche region represent the northernmost outpost for the species and the sole presence in the Diablo Range. That population has persisted because the area was never converted to crops or energy development, nor was it targeted for pesticide campaigns. But populations on Bureau of Land Management holdings in the area have experienced significant decline in recent years, for no apparent reason. To resuscitate the population, a captive breeding program has been established at the Fresno Chaffee Zoo. Several pairs of lizards were captured in the Panoche region as breeding stock, and their progeny have been released back into the wild to bolster the population. The California condor may be the signature captive breeding program in the region, but the blunt-nosed leopard lizard program may be just as important if the species is to persist in the Diablo Range.

About the Author

Joseph Belli has hiked and explored the Diablo Range extensively since the 1970s. He holds a master of science in conservation biology and has worked as a wildlife biologist for the National Park Service. He has conducted surveys for the Bureau of Land Management and California State Parks, and has worked with California condors, California red-legged frogs, and other sensitive or endangered species. Belli’s writing has appeared in High Country News, the Ponderosa, and The Wonder of It All, a collection of stories from National Park Service employees and volunteers. He lives on a rural property in the Diablo Range.

He has written two books:

• The Diablo Diary contains 25 natural history essays about the Diablo Range.
• Beneath a Black and White Sky: A Year Among Condors at Pinnacles National Park is his inside account of California condor reintroduction in Pinnacles National Park.

Image Captions and Credits

1. Blunt-nosed leopard lizard at the Carrizo Plain. Photo: Joseph Belli
2. Blunt-nosed leopard lizard in the Panoche region. Photo: Joseph Belli
3. Desert conditions in the Panoche region of the Diablo Range in June. Photo: Seth Adams
4. Grassland, sparse trees, and hills in the Panoche region of the Diablo Range in December. Photo: Al Johnson
5. Joseph Belli. Photo: Joan Hamilton

High resolution versions of images are available; please contact lkindsvater@savemountdiablo.org.