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July 27, 2026Sources cited
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Marine iguana

The marine iguana (*Amblyrhynchus cristatus*) is a lizard species endemic to the Galápagos Islands and the only lizard known to forage in the ocean.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 27, 2026|2 min read| Fact-checked

The marine iguana (*Amblyrhynchus cristatus*) is a species of lizard endemic to the Galápagos Islands and the only extant lizard known to forage in the ocean. It feeds primarily on marine algae and is adapted to life on rocky coasts and in cold seawater. The species is classified as Vulnerable by the IUCN.

Description

Marine iguanas are dark, stocky lizards with flattened tails and strong claws that help them swim and cling to rocks. Males may show brighter colours during the breeding season, while adults are often black or grey-black for much of the year.

Distribution and habitat

The species lives only in the Galápagos Islands, where it occupies rocky coasts, beaches, and intertidal areas. Its restricted range makes it endemic to the archipelago.

Behaviour and diet

Marine iguanas dive into coastal waters to graze on algae growing on rocks. They are herbivores and are especially notable for being the only lizards known to feed in the ocean.

Conservation

The species is considered Vulnerable, and its population faces pressures that can include invasive predators and environmental change. Conservation concern is heightened by its limited island distribution.

Key facts

  • The marine iguana is the only extant lizard that forages in the sea.
  • It is endemic to the Galápagos Islands and is found on rocky shores.
  • Its diet consists mainly of algae and seaweed.
  • The species is adapted for swimming and underwater feeding.
  • Marine iguanas are listed as Vulnerable.
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Canadian context

Canadian readers may encounter marine iguanas in zoos, aquariums, documentaries, and Galápagos tourism coverage; the species is also of interest in Canadian science and nature education because of its unusual marine adaptations.

Frequently asked questions

What is a marine iguana?
A marine iguana is a lizard species native only to the Galápagos Islands and adapted to feed in the ocean on algae.
Where do marine iguanas live?
They live only in the Galápagos Islands, where they are found along rocky shores and other coastal habitats.
What do marine iguanas eat?
They eat marine algae and seaweed, making them herbivores.
Why are marine iguanas unusual?
They are the only modern lizards known to forage in the sea and are specially adapted for swimming and underwater feeding.
Are marine iguanas endangered?
They are not currently listed as Endangered, but the IUCN classifies them as Vulnerable.

References

  1. National Geographic — https://www.nationalgeographic.com/animals/reptiles/facts/marine-iguana
    Supports: Scientific name, diet, size, lifespan, conservation status, ocean-foraging behaviour
  2. World Wildlife Fund — https://www.worldwildlife.org/species/marine-iguana
    Supports: Scientific name, habitat, ocean-going lizard description, Galápagos-only range
  3. Galapagos Conservation Trust — https://galapagosconservation.org.uk/species/marine-iguana/
    Supports: Endemic range, conservation status, size, lifespan, subspecies
  4. Oceana — https://oceana.org/marine-life/marine-iguana/
    Supports: Only lizard that forages in the ocean, Galápagos-only distribution, evolutionary origin