Lizards come in a dazzling array of colors, from bright greens to earthy browns. But some people wonder if the darker varieties like black lizards pose any special risks. If you’ve spotted a jet-black lizard scurrying by and want to know if you should be worried, read on.

If you’re short on time, here’s the quick answer: Most black lizards are not venomous or poisonous. Only the exotic Gila monster and Mexican beaded lizard produce venom. Common black lizards like skinks and swifts might look ominous but are harmless.

In this approximately 3000-word guide, we’ll cover everything you need to know about black lizard toxicity. We’ll identify venomous species to avoid, highlight harmless varieties, and describe lizard defense mechanisms.

We’ll also offer safety tips for coexisting with these mysterious backyard creatures.

Which Black Lizards Are Venomous?

The Gila Monster and Mexican Beaded Lizard

The only two venomous lizards native to North America are the Gila monster (Heloderma suspectum) and the Mexican beaded lizard (Heloderma horridum). These large, stocky lizards are found in the deserts of the American Southwest and Mexico.

Reaching up to 2 feet long, Gila monsters and Mexican beaded lizards are the largest lizards native to North America.

These lizards have venom-producing glands in their lower jaws which connect to grooved teeth. When they bite down, the venom flows into the wound. Though rarely fatal to humans, the venom causes severe pain and swelling.

Without treatment, bites can result in nausea, fainting, and an elevated heart rate lasting several days.

Gila monsters spend over 90% of their life underground in burrows or rocky shelters. They are most active at dawn, dusk, and at night during the spring and summer rainy seasons. Mexican beaded lizards are highly aquatic and are found near streams and seasonal ponds.

Difference Between Venomous and Poisonous

While the terms “poisonous” and “venomous” are sometimes used interchangeably, they have distinct meanings:

  • Poisonous animals or plants produce toxins internally as a defense mechanism. The toxins become dangerous when the animal or plant is touched or eaten.
  • Venomous animals inject toxins directly into another animal via bites or stings. Venom allows them to immobilize prey and plays an offensive, rather than defensive, role.

So while Gila monsters and Mexican beaded lizards produce their own venom internally, they use fangs to deliver it into their victims – making them venomous, not poisonous.

Venomous Animals Poisonous Animals
Snakes Dart frogs
Scorpions Pufferfish
Gila monsters Monarch butterflies

Researchers believe the Gila monster and Mexican beaded lizard evolved their venom separately from snakes. Though not often needed for hunting, the painful venom helps deter predators when threatened. It also may aid in digestion of food once swallowed.

To learn more about these fascinating lizards, visit the San Diego Zoo’s site on Gila monsters and Mexican beaded lizards.

Common Harmless Black Lizards


Skinks are a highly diverse family of lizards found worldwide. There are over 1,500 known species of skinks, making them one of the largest lizard families. Most skinks are small- to medium-sized, with elongated bodies and smooth, glossy scales.

Though some species are boldly patterned, many skinks are black or dark brown in coloration. This helps them blend into their environment and avoid predators.

Some of the most common harmless black skinks in North America include:

  • Common five-lined skink – Found throughout eastern and central US. Grows up to 8 inches long.
  • Broad-headed skink – Found in southeastern US. Grows up to 9 inches long.
  • Great Plains skink – Found in central US. Grows up to 7 inches long.

Skinks are primarily insectivores, feeding on crickets, spiders, beetles, and other small invertebrates. They are diurnal lizards, active during the day when hunting for food. At night, skinks take shelter in logs, rocks, or burrows.

One of the most unique features of skinks is their ability to shed their tails when threatened. The tail continues to wiggle after detaching, distracting the predator while the skink makes its escape. The tail eventually regrows, though it is slightly shorter than the original.


Swifts are a genus of relatively small lizards belonging to the Scincidae family. There are around 50 described species of swifts, most of which are found in Africa. However, a few swift species also occur in southern Europe and southwestern Asia.

Some characteristics of swifts include:

  • Slender bodies and long tails
  • Small heads and pointed snouts
  • Smooth, glossy scales
  • Short legs with five clawed toes on each foot
  • Coloration ranges from brown to black with some striping

The European swift (Scincus scincus) and Common swift (Scincus mitranus) are two nearly identical black swift species found around the Mediterranean region. They inhabit dry, sandy areas and scrublands. During the day, they burrow underground to avoid heat and predators.

At night, they emerge to hunt insects and other small prey.

Like other skinks, swifts are able to voluntarily shed their tails when grabbed. This helps them escape from predators in a pinch. Their tails later regenerate, though the new tail is usually shorter. Overall, swifts are harmless, mild-mannered lizards that tend to avoid humans.


Racerunners belong to the genus Aspidoscelis and are small, insect-eating lizards native to the Americas. There are around 50 recognized racerunner species, many of which have black coloration.

Some features of racerunners:

  • Slender bodies with long tails
  • Pointed heads and rounded snouts
  • Smooth scales that are sometimes keeled
  • Adult size ranges from 3 to 8 inches
  • Colors include solid black, gray, brown, and striped varieties

Well-known black racerunner species include:

Species Range
Black-throated racerunner Southwestern US, Mexico
San Joaquin whiptail California
Gila spotted whiptail Southwestern US

Racerunners thrive in arid habitats like deserts, chaparral, and grasslands. They are diurnal and spend their mornings basking in the sun to warm up. Later in the day, they actively forage on the ground for spiders, insects, and other small prey.

When threatened, racerunners can run extremely fast to zip away from predators.

Despite their speedy movements, racerunners are mild-tempered lizards that present no threat to humans. Their small size and insectivorous diet means they help control pest populations. Overall, the many black racerunner species are beneficial components of the ecosystems they inhabit.

Lizard Defenses and Bites

Toxicity vs. Infection Risk

While uncommon, some lizards like the Gila monster and Mexican beaded lizard produce venom that can be dangerous if enough is injected (but deaths are extremely rare). More concerning is the risk of infection from bacteria in the mouth of any lizard that breaks the skin.

According to the Centers for Disease Control, as many as 8,000 people per year receive medical treatment for infections from lizard bites in the U.S. alone. Common pathogens found in the mouths of lizards include Staphylococcus, Streptococcus, Clostridium, and Pasteurella bacteria.

Without treatment, these can cause serious swelling, necrosis of tissue, blood poisoning, and other nasty effects.

So while the toxins found in venomous lizards can’t compete with the lethality of certain snakes or spiders, the risk of complications from pathogens is considerable for many common pet lizards and wild ones as well.

Being chomped even by your cute bearded dragon could lead to an urgent care visit if you aren’t careful!

Avoiding Bites

The best way to prevent getting bitten is to respect a lizard’s space and pay attention to its signals. Stress, fear, hunger, mating behaviors, and territory issues can all trigger aggressive responses.

Here are some tips to avoid lizard bites:

  • Approach slowly and calmly if interacting with a lizard.
  • Don’t touch wild lizards.
  • Properly socialize pet lizards to handling.
  • Watch for signs of aggression like puffing up, hissing, head-bobbing, change of color, etc.
  • Don’t interact with lizards during breeding season or when protecting nests/young.
  • Always wash hands after contact to prevent bacteria transmission.

Paying attention to the lizard’s signals goes a long way. While bites can’t always be avoided, taking proper precautions greatly minimizes the likelihood you’ll become a statistic.

Coexisting Safely With Backyard Lizards

Lizards are common backyard visitors in many parts of the world. While surprising encounters may startle some homeowners initially, most species of lizards are harmless and can safely coexist with humans.

Learning how to identify local lizard species and understanding their behaviors is key to maintaining a safe environment.

Identifying Backyard Lizards

Common lizards found slithering through backyards include geckos, skinks, swifts, racers, whiptails, and fence lizards. These species come in an array of sizes and colors with distinct features:

  • Geckos have widened toe pads that allow them to scale vertical surfaces and even cling to ceilings.
  • Skinks and swifts typically have smooth, shiny scales and short, stubby legs or no legs at all.
  • Racers, whiptails, and fence lizards tend to be quick and agile with long tails.

While most people assume every lizard spotted is venomous or aggressive, less than 2% of lizard species worldwide are actually dangerous to humans. Non-venomous species common in backyards primarily eat small bugs and pose little threat.

Safely Observing Backyard Lizards

Encountering backyard lizards can be an exciting nature encounter. Here are some tips for safely observing these cold-blooded creatures:

  • View lizards from a distance as not to startle them. Sudden movements may cause them to dart away or detach their writhing tails.
  • Never attempt to touch or capture wild lizards. While they may appear friendly, surprising bites are possible.
  • Supervise curious children and pets around lizards. Chasing or disturbing them stresses the reptiles.
  • Research local species to identify those inhabiting your backyard. Understanding their feeding behaviors and habitat preferences aids coexistence.

Providing sheltered, vegetation-filled areas in the backyard creates an inviting habitat for beneficial lizard residents. Leaving these reptiles alone to carry out their vital bug consumption allows safe observation from afar.

When Lizards Pose Problems

On very rare occasions, lizards encroaching in high numbers close to homes can pose problems. Large aggregations may indicate ample food availability leading to rapid breeding. In these cases, proactive steps can restore balance:

  • Trim overgrown vegetation that harbors insects, providing the lizard’s food source.
  • Remove wood piles, rock walls, and debris that offer shelter for lizards to nest and breed.
  • Use sticky barriers or gentle repellents on home foundations to block access.
  • Contact local wildlife management authorities if high densities of lizards persist.

Following these coexistence tips allows most homeowners to enjoy lizard encounters safely. Educating ourselves on native species in backyards and their vital roles creates an appreciation for these unique reptiles slithering among us.


While exotic lizards carry venom, don’t let the dark coloration of common backyard lizards alarm you. Simple precautions like not handling wild lizards should keep you safe. And maintaining native plants and hiding spots helps these docile creatures thrive alongside us.

The next time you spy a swiftly scampering black lizard, you can appreciate its graceful movements without undue worry. Just let it be, and it’s likely to treat you the same way in return.

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