Imagine my surprise when, during a hike near Lake Tahoe, I paused to admire a lizard basking on a rock—only for a passing ranger to casually mention that it didn’t belong there at all. It was an invasive species, thousands of miles from home.
California’s wild spaces, from desert valleys to coastal forests, are increasingly being invaded by non-native reptiles. Whether they’ve escaped from backyard terrariums or hitched rides in cargo shipments, these unexpected guests are more than just out of place—they’re reshaping ecosystems.
Competing with native wildlife, spreading disease, and altering natural food webs, these reptilian outsiders are changing the very balance of California’s biodiversity.
1. Red-eared Slider: The Turtle Taking Over
With their bright red ear patches, these distinctive turtles—often released by well-meaning pet owners—have become California’s most widespread reptile invader. Originally from the Mississippi River basin, they’ve muscled their way into ponds and lakes across the state.
Red-eared sliders outcompete native western pond turtles for basking spots and food resources. They grow larger, reproduce faster, and tolerate poor water quality better than their native counterparts.
Fun fact: These turtles can live up to 30 years in the wild, creating a decades-long ecological impact after just one thoughtless tank-dumping incident!
2. Brown Anole: The Backyard Invader
These nimble brown lizards, now common on garden walls and fences across Southern California, first arrived as stowaways in potted plants shipped from Florida and the Caribbean. Their lightning-fast movements and adaptive nature have helped them establish thriving colonies in urban areas.
Males perform an impressive push-up display with their reddish dewlap (throat fan) extended to attract mates or defend territory. Unlike many invasives, brown anoles primarily occupy disturbed habitats where native lizards are already struggling.
They’re consummate bug-hunters, potentially altering insect populations in the neighborhoods they colonize.
3. Jackson’s Chameleon: The Living Dinosaur
With three horn-like projections on males’ heads and independently rotating eyes, these mini-dinosaurs from East Africa make unforgettable escaped pets. Their unusual appearance made them popular in the exotic pet trade, but their specialized needs often lead to releases.
Armed with projectile tongues that can extend to nearly twice their body length, Jackson’s chameleons snatch up native insects with surgical precision. They’ve established breeding populations in several California counties, particularly in coastal areas with moderate temperatures.
Surprisingly adaptable for such specialized creatures, they’ve learned to camouflage within California’s urban jungles just as effectively as their native forests.
4. Italian Wall Lizard: The Mediterranean Hitchhiker
Uninvited but thriving, Mediterranean reptiles slipped into California via plant shipments — and never looked back.
First spotted in San Pedro during the 1990s, they’ve since spread throughout Los Angeles County.
Quick and agile, Italian wall lizards display beautiful green, brown, and sometimes blue coloration. They’ve proven particularly adept at colonizing urban environments, where they scurry along walls and fences hunting insects.
Remarkably, these adaptable lizards have shifted their diet in California, consuming more plant material than their European counterparts – a behavioral change that helps them thrive in their adopted homeland.
5. Mediterranean House Gecko: The Nighttime Nuisance
Chirping like tiny birds at night, these pale, translucent geckos have taken up residence on California’s buildings. Unlike many reptiles, they’re comfortable around humans, often seen clinging to walls near porch lights, feasting on insects attracted to the glow.
Native to Southern Europe and North Africa, these nocturnal hunters arrived as stowaways in shipping containers. Their specialized toe pads allow them to scale vertical surfaces and even traverse ceilings with ease.
While not particularly harmful to native wildlife, their expanding presence represents yet another shift in California’s urban ecology, where non-native species increasingly dominate human-adjacent habitats.
6. Spiny Softshell Turtle: The Pancake Predator
Flattened like aquatic pancakes with leathery shells and tubular snouts, these odd-looking turtles have infiltrated California’s waterways. Native to eastern North America, they’ve been transported westward through the pet trade and deliberate introductions.
Experts at ambush, spiny softshells bury themselves in sandy or muddy bottoms with only their eyes and snout exposed, waiting for unwary prey. Their aggressive predatory behavior threatens native fish, amphibians, and invertebrates.
Surprisingly fast both in water and on land, these turtles can outswim most predators and quickly retreat to safety when startled – making them nearly impossible to eradicate once established.
7. Green Iguana: The Arboreal Giant
Reaching lengths of up to six feet, these herbivorous reptiles—once kept in captivity—have established small but stable colonies throughout Southern California. Pet owners often underestimate how large and demanding these Central American reptiles will become, leading to releases.
Primarily herbivores, green iguanas strip vegetation from trees and shrubs, potentially damaging native plant communities. Their burrowing habits can undermine riverbanks, seawalls, and even building foundations.
While cold-sensitive, California’s warming climate may allow these tropical lizards to expand their range northward, threatening more of the state’s ecosystems with their voracious plant-eating and destructive digging behaviors.
8. Southern Watersnake: The Wetland Warrior
Slithering through California’s marshes, these water-loving serpents have established populations in the Central Valley. Often mistaken for venomous cottonmouths (which aren’t native to California), these harmless but aggressive snakes will strike repeatedly when cornered.
Voracious predators, southern watersnakes feast on native fish, frogs, and salamanders – many of which are already threatened by habitat loss and pollution. Their ability to thrive in degraded aquatic environments gives them an edge over more sensitive native species.
Remarkably, females don’t lay eggs but give birth to live young – up to 30 at once – allowing populations to expand rapidly once established in suitable habitat.
9. Northern Watersnake: The Aquatic Ambusher
Easily confused with its southern cousin, this adaptable water-dwelling snake has quietly infiltrated California’s freshwater ecosystems. Reaching up to 4.5 feet long, these powerful swimmers patrol ponds, lakes, and slow-moving streams hunting for prey.
Northern watersnakes are generalist predators, consuming whatever aquatic creatures they can overpower – from native fish to amphibians to crayfish. Their introduction threatens California’s already imperiled native frog and fish populations.
Surprisingly, these snakes can remain submerged for nearly 30 minutes while hunting, allowing them to access prey unavailable to many native predators and giving them a competitive edge in their adopted California habitats.
10. Argentine Black-and-White Tegu: The Intelligent Invader
Intelligent and eye-catching, these black-and-white lizards from South America are changing what we know about reptile smarts. Growing up to four feet long and weighing 10+ pounds, tegus have begun appearing in California after establishing problematic populations in Florida.
Unlike most reptiles, tegus can regulate their body temperature, allowing them to remain active in cooler weather. They’re omnivorous opportunists, consuming everything from fruits and vegetables to eggs, small animals, and carrion.
Perhaps most concerning, these clever lizards can remember locations and routines, returning to productive feeding sites and learning to avoid traps – making them particularly difficult to control once established.