Marine iguana
Amblyrhynchus cristatus
Endemic Galápagos sea lizards bask on black lava, sneeze salt and graze algae at low tide. Watch quietly from park distance; sightings are not guaranteed.
Vulnerable (IUCN, 2020) means it is at high risk of extinction in the wild. Some island subspecies are assessed on their own, up to Critically Endangered.
Photos show the species, not always the places on this page.
Length
Varies a lot by island. In one measured group on San Cristóbal, adults averaged about 1 m (3.2 ft) from nose to tail, from about 0.7 to 1.2 m (2.4 to 4 ft); up to about 1.5 m (4.9 ft) is reported
Weight
Varies hugely by island: on Genovesa the largest weigh under 1 kg (2 lb), while on southwest Isabela big males can top 12 kg (26 lb). Males weigh about 70% more than females on average
Next to a person
On Genovesa an adult weighs about as much as a large water bottle; the biggest males on Isabela or Fernandina can weigh as much as a small dog
What it eats
Seaweed, mostly red algae and sea lettuce; a few populations also eat salty coastal plants.
Around people
Calm, give space
How it lives
About 95% of marine iguanas graze on seaweed uncovered at low tide; only the largest, mostly males, dive for seaweed farther offshore. Afterwards they bask on dark lava to warm up, and they gather in dense groups, especially on cool nights. In the month-long mating season, males become more colourful and defend small territories, and females lay 1 to 6 eggs in sandy burrows, which hatch after about 3 months.
Where it goes
Marine iguanas stay on their home island coast and do not migrate. Most dives are short and shallow. In cold water their heart rate slows, and afterwards they warm up again on the rocks.
We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.
Populations
Found only in the Galápagos, with 11 named island subspecies that differ in size, shape and colour. The largest live on Isabela and Fernandina, and some of the smallest on Genovesa. Breeding males on Española and Floreana turn vivid red and green. The species is Vulnerable, but several island subspecies are Endangered or Critically Endangered.
Meet it respectfully
Galápagos National Park rules apply: stay with your authorised naturalist guide and on marked trails, and keep at least 2 m (6 ft) from wildlife on land, snorkel and dive, even if an iguana comes closer. From a kayak, paddleboard or panga the rule is at least 4 m. Never touch, feed or chase them, never use flash, and watch where you step on lava and beaches, where females nest.
Fun fact
Tap the bulb to light it up.
It is the only lizard in the world that feeds in the sea.
It is not a land iguana. Galápagos land iguanas belong to a different genus and live inland.
Since March 2026, international commercial trade in marine iguanas is banned under CITES Appendix I.
When El Niño brings hunger, marine iguanas can shrink their skeleton by up to 20%, so they need less food to survive.
Source: Galapagos Conservation Trust, Marine iguana (see Wikelski & Thom, 2000, Nature)
Marine iguanas eat salty seaweed. They filter the extra salt from their blood at the nose and sneeze it out, often leaving salt crystals on their snouts.
Marine iguana in the Ocean Atlas
Places we have researched where this animal is recorded. It is never guaranteed, and some places are for watching from the boat only.
Travel with usComing soonTrusted referralExploringOn pause, story onlyEthics pass
Country colour: pink where we travel, blue where we are exploring or refer, grey for story only.
EcuadorRead more about the marine iguana
Sources for this page
- IUCN Red List, 2020
- Galápagos Conservation Trust
- Miralles et al., 2017
- Wikelski, 2005
- Lewbart et al., 2015
- IUCN SSC Iguana Specialist Group, 2020
- Galápagos Conservancy, park rules
- WoRMS, Amblyrhynchus cristatus
Facts checked 26 September 2026. Photos: Unsplash licence, or Creative Commons as shown on each photo.
Work in ocean travel?
We are always happy to hear from exceptional local operators, accommodation, conservation organisations and destination experts. If your work fits responsible, small-group ocean travel, we would love to learn more.
Partner with Ocean CallingShop with Ocean Calling
Visit the Ocean Calling storefront on Amazon.
As an Amazon Associate I earn from qualifying purchases. You are not only choosing products that respect the ocean, you are also helping us keep going: paying our local partners fairly and keeping our retreats ethical, sustainable and honestly priced for you. 💗