Marine Iguana in Galápagos: Facts and Where to See It

Land iguanas from South America are thought to have drifted to Galápagos on logs or other debris millions of years ago, and the marine iguana evolved from them. Charles Darwin called it "hideous-looking" and among the "most disgusting, clumsy lizards". Its body is built for a cold sea.

• Blunt snout, sharp teeth. They scrape algae off the rocks, the only food a marine iguana eats.
• Flat tail, long claws. The tail drives it through the water like a crocodile, and the claws hold on to rocks in strong currents.
• A slower heart. In the water its heartbeat drops to half its normal rate, which saves energy and lets it feed for longer.
• Salt sneezes. Glands at the nose filter the extra salt from the blood, and the iguana sneezes it out, which often leaves white crystals on its head.

Large adults swim out and dive to graze; small ones stay near the shore and feed in rock pools on algae left dry by the low tide.

Marine iguanas are not truly social, but they gather in large groups, above all on cold nights, when lying close together keeps them warm. In the morning they bask in the sun, their dark grey and black scales soaking up the heat, until they have enough energy to swim out and feed. That is why the shore at Punta Espinosa on Fernandina, the largest colony in the archipelago according to the guide records, can look like a field of dark rock that moves.

For most of the year, adults are black. In the mating season, which the Galapagos Conservation Trust places between January and March, males change colour, and each island has its own: on Española and Floreana they turn bright red and green, on Santa Cruz red and black, on Fernandina dull green and brick red. Males fight for dominance over groups of females and defend them fiercely against rivals. The guide records place the red and green males at Punta Suárez on Española from December to March.

Marine iguana habitat is the rocky coast of nearly every island in Galápagos: the lava shore above the waterline for basking, and the sea below it for feeding. Its diet is red and green algae and seaweed, grazed from rocks underwater or in pools at low tide. Each island has iguanas of its own size, shape and colour.

Food decides how many survive. In El Niño years the warm water cuts the algae, and the population can fall by up to 85 percent. Marine iguanas can even shrink their skeleton by up to 20 percent to need less food, and grow back when conditions improve.

Guide sighting records list marine iguanas at 6 visitor sites on 6 islands, and the guides note them as present along the coasts of the whole archipelago. 2 sites are rated Likely, with sightings on most visits: Punta Espinosa on Fernandina, with the archipelago's largest colony, and Punta Suárez on Española, where the males turn red and green. The other sites are rated Possible or Rare, among them the trail on South Plaza and Las Tintoreras off Isabela.

Marine iguanas are in Galápagos in all 12 months, so no month rules them out. The colourful males of Española are the one thing tied to a season: the guide records place them from December to March, and the Galapagos Conservation Trust gives January to March for mating. In the next twelve months, 822 departures stop at a site where they are seen.

The marine iguana is listed as Vulnerable. How many there are is not well known; the Galapagos Conservation Trust funds a drone survey, Iguanas from Above, to count them for the first time across the islands. Cats, dogs and rats brought by people eat eggs and young iguanas, which cannot defend themselves against large land predators. El Niño, oil spills and plastic in the sea add to the pressure.

Protection. In 2025, all Galápagos iguana species were moved to CITES Appendix I, the highest level of protection, which prohibits all international commercial trade. Galápagos National Park rules keep visitors at least 2 metres (6 feet) from wildlife and on marked trails with a naturalist guide, which matters on shores where iguanas lie across the path.

1. Looking only on the beach. Marine iguanas lie on black lava, and against it they are easy to step past. Watch where you walk.
2. Expecting colour all year. The red and green males of Española appear from December to March; the rest of the year they are dark.
3. Expecting them to swim in the morning. They bask first and go to sea once they are warm.
4. Getting too close. Park rules set at least 2 metres between visitors and wildlife, and a sneezing iguana is a sign to step back.