Quick Answer
- Spiny-tailed iguanas are the genus Ctenosaura, a group of more than a dozen species from Mexico and Central America.
- The best known is the black spiny-tailed iguana (Ctenosaura similis), often simply called the "black iguana."
- It is often cited as the fastest-running lizard, with a reported top speed of about 21 mph (34 km/h).
- Large adults reach about 3–4 feet including the tail.
- Black spiny-tailed iguanas are invasive in South Florida, where they eat a wide range of plants and animals.
What Are Spiny-Tailed Iguanas?
Spiny-tailed iguanas get their name from the rings of sharp, enlarged spiny scales around their tails. They are related to green iguanas but are generally smaller, faster, more ground-dwelling and more omnivorous. In Central America they are widely known as garrobos, and in parts of their range they are hunted for food.
The group includes widespread species such as the black spiny-tailed iguana and the Mexican spiny-tailed iguana (Ctenosaura pectinata), as well as small island species with very restricted ranges, such as the critically endangered Utila spiny-tailed iguana of Honduras.
Black Spiny-Tailed Iguana at a Glance
| Trait | Details |
|---|---|
| Scientific name | Ctenosaura similis |
| Other names | Black iguana, black ctenosaur, garrobo |
| Native range | Southern Mexico through Central America |
| Size | Up to about 4 ft including tail; many adults closer to 3 ft |
| Color | Juveniles bright green; adults gray, tan or black with dark bands |
| Diet | Omnivore: plants, insects, eggs and small animals |
| Speed | Reported up to about 21 mph |
| Lifespan | Reported up to about 25 years |
Appearance
Adult black spiny-tailed iguanas are usually gray, tan or blackish with dark crossbands, a row of spines along the back and a tail ringed with sharp spines. Hatchlings are bright green, which is one reason they are sometimes confused with young green iguanas. Adults are easier to tell apart:
| Feature | Black spiny-tailed iguana | Green iguana |
|---|---|---|
| Tail | Rings of sharp, spiky scales | Smooth with dark bands |
| Cheek | No large round cheek scale | Large round subtympanic shield |
| Adult color | Gray, tan or black | Green, gray, brown or orange |
| Lifestyle | Mostly ground and rocks, also climbs | Mostly trees, near water |
| Diet | Omnivorous | Mainly herbivorous |
The Fastest Lizard?
The black spiny-tailed iguana is often cited as the fastest-running lizard on Earth, with a reported top speed of about 21 mph (34 km/h). Whatever the exact record, they are very quick over short distances and usually escape by sprinting to a burrow or rock crevice.
Diet
Young spiny-tailed iguanas eat mostly insects. Adults eat more plants, including leaves, flowers and fruit, but remain opportunistic. In Florida, black spiny-tailed iguanas have been reported eating crabs, birds and their eggs, small lizards, rodents, and even sea turtle hatchlings and young of their own kind, which is one reason they concern wildlife managers.
Spiny-Tailed Iguanas in Florida
Black spiny-tailed iguanas have been established in South Florida since around the late 1970s, likely after several releases. They now occur in parts of southeast Florida, the Keys and the Gulf coast, with a well-known population on Gasparilla Island. The Mexican spiny-tailed iguana also has smaller established populations in Florida.
Like green iguanas, they dig burrows that can undermine seawalls, sidewalks and foundations, and they damage landscaping. Because they eat animals as well as plants, they may also threaten native wildlife. Their legal status in Florida is similar to that of green iguanas: they are nonnative and may be removed humanely. See how to get rid of iguanas and our Florida iguana guide.
Are Spiny-Tailed Iguanas Dangerous?
They are not venomous and avoid people, but they are known for defensive behavior. If handled or cornered, they bite hard, scratch and lash their spiny tails. They are not commonly kept as pets for this reason, though some keepers do keep captive-bred spiny-tailed iguanas. Read more about bites in our guide on whether iguanas bite.
Frequently Asked Questions
What Is a Black Iguana?
"Black iguana" usually means the black spiny-tailed iguana, Ctenosaura similis, a Central American species that is also invasive in South Florida.
How Fast Is a Spiny-Tailed Iguana?
The black spiny-tailed iguana is often cited as the fastest lizard, with a reported top speed of about 21 mph.
Do Spiny-Tailed Iguanas Eat Meat?
Yes. They are omnivores and eat insects, eggs and small animals as well as plants, especially when young.
Are Spiny-Tailed Iguanas in Florida?
Yes. Black spiny-tailed iguanas have established populations in parts of South Florida, the Keys and the Gulf coast.
Sources: Wild South Florida, Black Spiny-Tailed Iguana; Five Sisters Zoo, Black Spiny-Tailed Iguana; Reptiles Magazine, Spiny-Tailed (Black) Iguana.
