Marine iguana crawling over seaweed-covered rocks in the surf

Marine Iguana: Facts, Photos & Why It’s So Strange

Amblyrhynchus cristatus

The world’s only lizard that goes to sea

Charles Darwin called them “imps of darkness”. Black, spiky and crusted with salt, marine iguanas lie in heaps on the rocks of the Galápagos – then dive into the cold ocean to graze on seaweed. No other lizard on Earth does that.

Marine Iguana vs. you

Your heightft / incm ft in5 ft 7 in

Highlights

The only sea-going lizard
Highlights

It sneezes salt
Highlights

Shrinks when food runs out

Size: ~4 ft; Up to 4 ft (1.3 m) long on some islands, much smaller on others
Weight: 1.1–26 lb; 1.1–26 lb (0.5–12 kg), depending on the island
Lifespan: ~12 years; About 12 years on average, sometimes far longer
Left in the wild: ~200,000; Probably around 200,000

Conservation status

Least Concern
Near Threatened
Vulnerable (this animal)
Endangered
Critically Endangered
Extinct in the Wild
Extinct

Vulnerable

Superpowers

Venomous : Is it venomous? No
Glows : Does it glow? No
Regenerates limbs : Can it regenerate limbs? No

Identity

Scientific name: Amblyrhynchus cristatus
Class: Reptile (lizard)
First described: 1825, by Thomas Bell

Life & family

Diet: Algae and seaweed
Gestation: None – the eggs hatch after about 3 months
Offspring: 1–6 eggs
Predators: Hawks and snakes; cats and dogs brought by people

Where to find it

Habitat: Rocky shores and the shallow sea next to them
Lives in: The Galápagos Islands – and nowhere else
In the wild: Yes – on almost any Galápagos shoreline
In zoos: No

Explore similar

Why is this animal unusual?

It can dive more than 66 ft (20 metres) deep and stay under for half an hour, slowing its heartbeat to save oxygen while it scrapes algae off the rocks.

Why does it look like that?

A blunt snout for grazing close to the rock, long claws for holding on in the surf, a flattened tail for swimming and dark skin that soaks up heat after a cold dive.

Strangest biological feature

Salt sneezing. It swallows a lot of seawater with its food, so special glands collect the salt and the iguana sneezes it out. The spray dries into a white crust on its head.

Why is it strange?

When food runs out during El Niño years, marine iguanas shrink. Not just thinner – actually shorter, by up to 20%. When the algae return, they grow again.

Interesting behavioral facts

After a dive it’s so cold it can barely move, so it sprawls on hot lava rock, often piled on top of its neighbours.

Records held

The only lizard in the world that feeds in the sea.

Dark marine iguana with a spiky back on black volcanic rocks by the sea

Marine Iguana: quick answers

Are marine iguanas dangerous?

No. They eat only algae and seaweed and are famously relaxed around people. In the Galápagos, visitors must keep their distance anyway.

Why are marine iguanas black?

Dark skin soaks up heat from the sun quickly, which matters after a dive into cold water. In the breeding season, males on some islands turn red and green.