Welcome to the World of Marine Iguana
Marine Iguana
Amblyrhynchus cristatus
Also known as: Sea iguana
Average lifespan: 10–15 years (some live longer)
Primary habitat: Rocky shorelines and coastal areas
Geographic range: Galápagos Islands
Overview
The marine iguana is the only lizard in the world that forages in the ocean. Found exclusively on the Galápagos Islands, it has evolved unique adaptations that allow it to swim, dive, and feed on marine algae. Its survival is closely tied to the health of coastal marine ecosystems.
What It Looks Like
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Stocky, flattened body
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Dark gray to black coloration
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Spiky crest running along the back and tail
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Long, laterally flattened tail for swimming
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Strong claws for gripping rocks
How It Behaves
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Mostly active during the day
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Often seen in large groups while basking
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Enters the ocean to graze on algae
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Relies on sunbathing to regulate body temperature
What It Eats
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Marine algae and seaweed
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Occasionally feeds underwater or in tidal zones
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Strictly herbivorous
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Grazes repeatedly throughout the day
Life Cycle
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Breeding occurs during the dry season
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Females lay 1–6 eggs in burrows
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Eggs incubate for several months
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Hatchlings are independent at birth
Survival Skills
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Ability to swim and dive efficiently
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Flattened tail for propulsion
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Salt glands that expel excess salt through sneezing
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Dark coloration helps absorb heat after swimming
Fast Facts
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The only marine-feeding lizard on Earth
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Can dive over 30 feet deep
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Sneezes salt from its nose
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Inspired Charles Darwin’s early evolutionary observations
Conservation
Marine iguanas play a unique role in the Galápagos ecosystem as the only lizards that feed in the ocean, grazing algae and helping keep coastal marine habitats balanced. They are threatened by climate change—especially El Niño events that reduce algae availability—as well as invasive predators, pollution, and human disturbance. Conservation efforts focus on protecting the Galápagos Islands, controlling invasive species, limiting human impact, and long-term monitoring to help marine iguanas survive in a rapidly changing environment.​