# Galápagos Marine Iguana (*Amblyrhynchus cristatus*)

The Galápagos Marine Iguana is a unique lizard that can swim in the ocean. It has dark skin and spiky crests on its back. These iguanas love basking in the sun on rocky shores.

- **Category:** [Reptiles](https://www.snappit.app/explore/categories/reptile)
- **Rarity:** Common
- **Danger:** 1/5 · Very low
- **Habitat:** Coastal areas
- **Also known as:** Marine Iguana

![Galápagos Marine Iguana](https://media.snappit.app/site-media-v1/0ee56e5212e971a8182003dadd8df8f6bc706d20b87b1077555d4142b4af2735/image-560x560/w-560.webp)

## Appearance

The Galápagos Marine Iguana is a uniquely dark-colored lizard, often black or mottled grey, with some individuals displaying reddish or greenish hues during breeding. It has a prominent spiky dorsal crest, a blunt snout, and a flattened, paddle-like tail, making it visually distinct from land iguanas.

## Taxonomy

- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Squamata
- **Order:** Lacertilia
- **Family:** Iguanidae
- **Genus:** Amblyrhynchus

## Marine iguana, up close

The marine iguana (Amblyrhynchus cristatus) lives only on the Galápagos Islands, on the black lava shores of almost every island. It is the only lizard in the world that finds its food in the sea. Adults graze on red and green seaweed (algae), and the biggest males dive for it. The sea there is cold, so after each trip they warm up again by basking on the rocks. Extra salt from their food comes out through glands in the nose, with a loud sneeze. In El Niño years, when warm water kills off the algae, many starve, and the survivors can actually shrink. Males are much bigger than females, and on islands like Española they turn red and green in the breeding season.

Also called: Galápagos marine iguana, Sea iguana.

The only lizard that feeds in the sea: it dives for seaweed, sneezes out salt and can even get shorter when food runs out. Spin it, tap it, then test yourself.

### Special abilities

- **Seaweed Diver** (≈15 m usual depth for big divers): Big marine iguanas swim out from the shore and dive to the sea floor to graze on algae. No other lizard in the world finds its food in the sea. [1][5][2][11]
  - Iguanas heavier than about 1.8 kg dive to around 15 m and stay down for up to 20 minutes. Large adults have been reported diving below 30 m.
  - Smaller iguanas mostly stay out of deep water. They graze on rocks that the low tide has uncovered.
  - Even so, marine iguanas spend only about 5% of their time at sea. The rest is spent resting and basking on land.
  - In a 1965 lab test, iguanas held underwater for 30–50 minutes stayed calm, and their heartbeat slowly got slower.
- **Rock Grazer** (red + green algae make up most of its food): A marine iguana presses its blunt face against the rocks and scrapes off the thin red and green algae that grow there. It is a plant-eater that grazes like a cow, but under the sea. [5][21][6][1]
  - Its main foods are red and green algae, such as sea lettuce (Ulva).
  - Its sharp, pointed teeth scrape the algae off the rock.
  - In 1835 Charles Darwin opened the stomachs of several marine iguanas and found nothing but minced seaweed.
  - Now and then it eats other things too, such as beach plants, crabs and insects.
- **Salt Sneeze** (achoo! how the salt comes out of its nose): Seaweed and seawater bring far too much salt into an iguana's body. Glands in the nose pull the salt out of the blood, and the iguana blasts it out with a sneeze. [1][21][6][20]
  - After feeding, marine iguanas go back to their resting spots and 'sneeze' out the extra salt.
  - The salty spray often lands back on the head, leaving a white crust on the head and snout.
  - Darwin noticed that a frightened marine iguana would squirt a drop of fluid from each nostril.
  - In 1958, scientists showed that sea-going reptiles, including this iguana, get rid of salt through special glands.
- **Shrink to Survive** (up to 20% shorter after an El Niño famine; still debated): In El Niño years the sea warms up, the algae die back and marine iguanas go hungry. Instead of only getting thinner, adults can get shorter, and smaller iguanas need less food to stay alive. [3][4][5]
  - Martin Wikelski and Corinna Thom used 18 years of measurements from two islands. Iguanas shrank by up to 6.8 cm (up to 20% of their length) in two-year spells: 1982–83, 1987–88, 1992–93 and 1997–98, all El Niño years.
  - Bigger iguanas shrank the most, and the ones that shrank survived longer. When food came back, the survivors grew longer again.
  - Losing soft tissue between the bones could not explain so much shrinking, so the scientists think the bones themselves get shorter. Exactly how is still being studied.
  - A 2025 study found that during El Niño, iguanas also used about 20% less energy when resting.
- **Solar Recharge** (2× faster at warming up than at cooling down): The Galápagos sea is cold, so an iguana loses heat every time it swims. It warms up again by lying flat on the black lava with its legs spread out, soaking up the sun. [1][11][12][2]
  - Marine iguanas bask for the first hours after sunrise and usually go into the sea at about 7:30–8:00 in the morning.
  - In a 1965 study, they warmed up about twice as fast as they cooled down, in air and in water. Changes in blood flow and heart rate help them hold on to heat.
  - On summer days, their average body temperature ranges from about 27 °C to 35 °C.
  - Their dark colour helps them absorb heat faster.
- **Paddle Tail** (flat tail shape: a side-to-side paddle): A marine iguana swims like a little crocodile. It presses its legs against its sides and wiggles its body and flat tail from side to side. [6][1]
  - Darwin described it swimming 'with perfect ease and quickness' by a snake-like movement of its body and flattened tail, with its legs held still.
  - Near the bottom, it sometimes pulls itself over rough ground with its feet.
  - Darwin threw one into a rock pool several times. Each time it swam straight back to the spot where he stood.
  - He guessed that the iguana feels safe on land, where it had no enemies, while at sea sharks may catch it.
- **Head-Butting Duel** (up to 45 females that may mate with one top male): In the breeding season, males each defend a small patch of shore. They bob their heads to warn rivals, and if that fails, they push head to head until one gives up. [1][9]
  - A male's display territory measures about 1.2–38.8 m², from about the size of a kitchen table to a large bedroom.
  - Fights are head-to-head shoving matches and can sometimes cause serious wounds.
  - The largest males win most of the matings, with up to 45 females in a season.
  - Choosing is hard work for females too: over 30 days, females ready to mate spent about three-quarters of a whole day's energy just on choosing a mate.
- **Bird Alarm Listener** (45% vs 28% went on alert to alarm calls vs normal song): Marine iguanas make no calls of their own, but they listen in on Galápagos mockingbirds. When a mockingbird gives its alarm call, many iguanas raise their heads and watch for danger. [8]
  - Galápagos hawks hunt both marine iguanas and mockingbirds, so a mockingbird alarm is useful news for an iguana.
  - In 2007, scientists on Santa Fé played recordings to groups of iguanas. About 45% became alert to the alarm call, but only about 28% to a mockingbird's normal song.
  - It was the first evidence that an animal without a voice of its own can recognise another species' alarm call.
  - Nobody knows yet whether the iguanas learn what the call means or are born knowing it.

### Body parts

- **Knobbly head** [21][1]
  - The top of the head is covered in rounded, knobbly scales.
  - It often looks white on top. That crust is dried salt that the iguana has sneezed out of its nose.
  - Rival males push head to head when they fight over a patch of shore.
- **Salt-sneezing nose** [21][1][20]
  - Special glands remove extra salt from the iguana's blood.
  - The salt leaves through the nostrils in a forceful snort that looks like a sneeze.
  - Scientists described these nasal salt glands in marine reptiles, including this iguana, in 1958.
- **Blunt snout** [1][21][23]
  - Amblyrhynchus means 'blunt snout'. Its face is much shorter and blunter than a land iguana's.
  - It uses its sharp, pointed teeth to scrape algae off the rocks.
  - A 2022 study of its skull found that the snout and teeth are built differently from those of every other iguana.
- **Spiky crest** [1]
  - A row of spines runs down the neck and back. Cristatus means 'crested'.
  - Adult males have a taller crest than females.
  - When a male warns off a rival, he bobs his head up and down.
- **Gripping claws** [21][6]
  - Each toe ends in a long, strong, curved claw.
  - The claws hook into rough lava and help the iguana cling on when waves and currents pull at it.
  - Charles Darwin noticed that the claws were well suited to crawling over rugged lava.
- **Paddle tail** [1][2][6]
  - The tail is flattened from side to side, like a paddle. Land iguanas have rounder tails.
  - Swinging it from side to side pushes the iguana through the water.
  - It makes up more than half of a big male's length.
- **Sooty black skin** [1][2]
  - Most marine iguanas are blackish, the same colour as the lava they sit on.
  - Dark skin soaks up the sun's heat quickly, which helps after a swim in cold water.
  - On Española and Floreana, top males turn red with green or blue legs in the breeding season.
- **Algae-fermenting gut** (≈60% of the food in its gut sits in the big colon) [10][1]
  - Seaweed is hard to digest. Bacteria in the iguana's large colon (the last part of the gut) break it down.
  - In a 2004 study, the colon held about 60% of all the food in the gut and the stomach about 32%.
  - Hatchlings eat adult droppings to pick up these helpful microbes.
- **Scent glands** [29]
  - Under the thighs are femoral glands, which ooze a waxy secretion.
  - A 2017 study found that the main ingredient is cholesterol, mixed with fatty acids.
  - Top males with more females nearby had more of one fatty acid, which may act as a scent signal.

### Stats

| Stat | Value | Notes |
|---|---|---|
| Length | up to 1.33 m | including the tail; males up to 133 cm, females up to 78.5 cm [1] |
| Weight | 0.9–3.5 kg | heaviest males: 0.9 kg on Genovesa, 3.5 kg on Santa Fé; islands differ up to tenfold; Males are about twice as heavy as females [13] |
| Dive depth | ≈15 m | usual for big divers; large adults reported below 30 m [1][5] |
| Dive time | up to 20 min | for iguanas heavier than about 1.8 kg [1] |
| El Niño shrinking | up to 20% | of body length (up to 6.8 cm) in two years [3][4] |
| Body temperature | 27–35 °C | lowest and highest daily averages in the wild in summer [12] |
| Eggs per clutch | 1–6 | laid in a burrow dug in sand [1][2] |
| Time to hatch | 89–120 days | about 3–4 months, with no parent care [1] |
| Population | 37,000–280,000 | estimated total in 2004; up to 8,000 per km of coastline in places [14][1] |
| Lifespan | up to ≈30 years | estimated maximum in the wild [1] |

### Photos

- [An adult on the lava at Las Bachas, Santa Cruz: spiky crest, strong claws and a long flattened tail](https://commons.wikimedia.org/wiki/File:Iguana_marina_(Amblyrhynchus_cristatus)%2C_Las_Bachas%2C_isla_Santa_Cruz%2C_islas_Gal%C3%A1pagos%2C_Ecuador%2C_2015-07-23%2C_DD_23.jpg) (photo: Diego Delso, CC BY-SA 4.0)
- [Feeding underwater off Fernandina, claws hooked into a rock covered in green and red algae](https://commons.wikimedia.org/wiki/File:Marine_Iguana_(Amblyrhynchus_cristatus)_feeding_underwater_off_Fernandina_Island%2C_Gal%C3%A1pagos_Islands.jpg) (photo: Sodacan, CC BY-SA 4.0)
- [Swimming near Santa Cruz with only the head and spiky back above the water](https://commons.wikimedia.org/wiki/File:Marine_iguana_swimming_near_Santa_Cruz_Island_Gal%C3%A1pagos_Ecuador_DSC00263_ad.JPG) (photo: Adavyd, CC BY-SA 4.0)
- [Two Española iguanas with white crusts of dried salt on their heads](https://commons.wikimedia.org/wiki/File:Espanola_Marine_Iguana_(Amblyrhynchus_cristatus_venustissimus).jpg) (photo: Gregory "Slobirdr" Smith, CC BY-SA 2.0)
- [A red-coloured marine iguana on a beach on Española](https://commons.wikimedia.org/wiki/File:20180810-Marine_iguana_on_Espa%C3%B1ola_Island_(0105).jpg) (photo: Nicolas Völcker, CC BY-SA 4.0)
- [A juvenile on Isla Lobos: grey, small and with only a tiny crest](https://commons.wikimedia.org/wiki/File:Iguana_marina_(Amblyrhynchus_cristatus)%2C_isla_Lobos%2C_islas_Gal%C3%A1pagos%2C_Ecuador%2C_2015-07-25%2C_DD_47.JPG) (photo: Diego Delso, CC BY-SA 4.0)
- [Two males shoving head to head at Punta Espinosa, Fernandina](https://commons.wikimedia.org/wiki/File:Fighting_Marine_Iguanas_(6519185111).jpg) (photo: Andrew Turner from Washington, DC, United States, CC BY 2.0)
- [Close up: knobbly scales on the head and tall spines on the neck](https://commons.wikimedia.org/wiki/File:One_of_a_Kind_(28749945267).jpg) (photo: Andy Morffew from Itchen Abbas, Hampshire, UK, CC BY 2.0)
- [Basking with legs spread on Plaza Sur, while a little lava lizard hunts behind](https://commons.wikimedia.org/wiki/File:Marine_iguana_01.jpg) (photo: Bernard Gagnon, CC BY-SA 4.0)
- [Marine iguanas on the beach at Tortuga Bay, Santa Cruz, beside the mangroves](https://commons.wikimedia.org/wiki/File:Iguanas_marinas_(Amblyrhynchus_cristatus)%2C_Bah%C3%ADa_Tortuga%2C_isla_Santa_Cruz%2C_islas_Gal%C3%A1pagos%2C_Ecuador%2C_2015-07-26%2C_DD_28.JPG) (photo: Diego Delso, CC BY-SA 4.0)

### Questions

- **Why do marine iguanas sneeze?** To get rid of salt. Eating seaweed brings in lots of salt, so glands in the nose take it out of the blood and the iguana sneezes it out. The spray often dries into a white crust on its head. [21][1]
- **Can marine iguanas breathe underwater?** No. They hold their breath. Big iguanas usually stay down for up to about 20 minutes, and their heart slows down while they are underwater. [1][11]
- **Do marine iguanas really shrink?** Yes. In El Niño famines, adults shrank by up to 20% of their length, and smaller iguanas were more likely to survive. When food returned, they grew longer again. [3][4]
- **What do marine iguanas eat?** Mainly red and green algae (seaweed), grazed from rocks at low tide or on dives. Now and then they also eat other things, such as beach plants, crabs or insects. [5][1]
- **Where do marine iguanas live?** Only on the Galápagos Islands of Ecuador, along the rocky coasts, beaches and mangroves of almost every island. [1][2]
- **Are marine iguanas dangerous?** No. They eat seaweed, and Darwin noticed that they did not even try to bite when caught. Still, they are wild animals, so watch them from a distance. [6][5]
- **Are marine iguanas endangered?** They are listed as Vulnerable. They live nowhere else, and El Niño famines, cats, dogs, rats and oil spills can kill many of them. [22][14][16]

### Marine iguana myths and facts

Sea dragons, salty heads and shrinking lizards. Here is what the evidence says.

- "Charles Darwin invented the name 'imps of darkness'." **Myth!** In his 1835 diary Darwin wrote 'Somebody calls them imps of darkness'. The phrase came from an earlier book about the voyage of HMS Blonde, which he had read. [7]
- "Marine iguanas go to sea to catch fish." **Myth!** They eat seaweed. Darwin found only seaweed in their stomachs, and they only rarely eat animals such as crabs or insects. [6][1]
- "The white stuff on their heads is salt." **Fact!** They sneeze extra salt out of their noses, and it dries into a white crust on the head and snout. [21]
- "Marine iguanas spend most of their time in the sea." **Myth!** They spend only about 5% of their time at sea. Most of the day they rest and bask on the rocks. [1]
- "A grown-up lizard can never get shorter." **Myth!** Adult marine iguanas shrank by up to 20% of their length during El Niño famines, then grew again when food returned. [3][4]
- "They shrink because their bones get shorter." **Not proven!** Shrinking soft tissue alone cannot explain how much they shrink, so scientists think bone is broken down too. How it works has not been fully shown. [3][4]
- "Every marine iguana dives to the sea floor." **Myth!** Only big iguanas dive. Smaller ones graze on rocks that are uncovered at low tide. [1][2]

### The life of a marine iguana

From an egg in a sandy burrow to a big diver on the lava.

- **Breeding season**: Males fight for a patch. The timing varies by island, but it is often around December and January. Males defend small territories with head bobs and head-butting. [1]
- **About a month after mating**: A nest in the sand. The female digs a burrow 30–80 cm deep and lays 1–6 eggs. Some females walk 300 m or more inland to nest. [1][2]
- **89–120 days**: Eggs on their own. The eggs develop underground with no parent looking after them. Mockingbirds sometimes eat them. [1]
- **Hatching**: Collecting gut helpers. Hatchlings eat the droppings of adults. That gives them the microbes they need to digest algae. [1][10]
- **Young iguana**: Low-tide grazer. Small iguanas feed on rocks uncovered by the low tide and hide in cracks when danger comes. Galápagos hawks catch many young ones. [1][8]
- **Adult**: Big enough to dive. Iguanas heavier than about 1.8 kg swim out and dive for algae, often about 15 m down. [1]
- **El Niño years**: Famine and shrinking. Warm water kills off the algae. Up to 90% of some populations may die, and survivors can shrink. In good years that follow, they grow again and females breed younger. [14][3][4]
- **Up to ≈30 years**: Old age. The longest a wild marine iguana is thought to live is about 30 years. [1]

### Marine iguana vs Galápagos land iguana vs green iguana

Three big iguanas that people mix up. Check the colour, the tail and the food.

| | Marine iguana | Galápagos land iguana | Green iguana |
|---|---|---|---|
| Scientific name [1][24][25] | Amblyrhynchus cristatus | Conolophus subcristatus | Iguana iguana |
| Home [1][24][25] | Galápagos shores only | Dry inland areas of some Galápagos islands | Mexico to Paraguay and Brazil, and Caribbean islands |
| Colour [1][24][26] | Blackish (some breeding males red and green) | Yellowish | Green, olive, grey or orange |
| Tail [1][6][26] | Flattened like a paddle | Round | Long, with dark bands |
| Main food [1][24][25] | Seaweed (algae) | Cacti, grasses and leaves | Leaves, flowers and fruit |
| Biggest males [1][24][25] | About 1.33 m long | About 1.07 m long | About 2 m long |
| Eggs per clutch [1][24][26] | 1–6 | 8–22 | 10–70 |
| IUCN status [22][24][27] | Vulnerable | Vulnerable | Least Concern |

A black iguana sitting on the shore or swimming in the sea is a marine iguana. A yellow one inland is a land iguana. On Plaza Sur the two have occasionally produced hybrids.

### Blunt snouts, imps and Godzilla

Where the marine iguana's names come from, and how many kinds there are.

- **Amblyrhynchus cristatus**: Amblyrhynchus comes from Greek words meaning 'blunt snout'. Cristatus is Latin for 'crested', after the spines on its back. [1]
- **Imps of darkness**: An early visitor said they sat on the black lava 'like so many imps of darkness'. Darwin borrowed the phrase in his 1835 diary. [7]
- **Eleven island forms**: A 2017 study kept the marine iguana as one species but split it into 11 subspecies that differ in size, shape, colour and genes. [18][1]
- **Godzilla**: One of the five new subspecies, from Punta Pitt on San Cristóbal, was named A. c. godzilla. [18]
- **Cousin of the land iguanas**: A 2015 genome study estimated that marine iguanas split from the Galápagos land iguanas about 4.5 million years ago. [30]

### Is the marine iguana endangered?

It is listed as Vulnerable. There can be thousands on one stretch of coast, but the species lives nowhere else on Earth.

- **IUCN Red List:** Vulnerable (VU). Listed as Vulnerable because it lives in such a small area: all its shores add up to less than 500 km². El Niño famines, introduced predators and pollution are its main threats. [22][1]
- IUCN Red List (via GBIF)
- **Threat: El Niño famines**: When warm water kills the algae, 10–90% of a population can die. Stronger or more frequent El Niños could make this worse. [14][15][5]
- **Threat: Introduced predators**: Cats, dogs, rats and pigs brought by people eat eggs and young iguanas, and dogs also kill adults. Females are at risk when they travel inland to nest. [1][2]
- **Threat: Oil pollution**: After a tanker ran aground in 2001, 62% of the marine iguanas on Santa Fé died within a year, even though only a little oil reached the island. Iguanas on islands the oil did not reach did not decline. [16][17]
- **Threat: Small, separate populations**: Some island populations are tiny and genetically distinct, such as one on north-eastern San Cristóbal. On Marchena, iguanas showed signs of losing genetic variety, possibly because of the 1997–98 El Niño or a 1991 volcanic eruption. [1][18][15]
- **Helping: Keep out pets and pests**: Cats, dogs and rats are a danger to eggs and young iguanas, so keeping them away from nesting areas helps. [2][1]
- **Helping: Keep the sea clean**: The 2001 spill showed that even small amounts of oil can kill many iguanas, possibly by killing the gut microbes they need to digest algae. [17][16]
- **Galápagos land iguana** (VU): The marine iguana's closest relative, with fewer than 10,000 mature adults, threatened by introduced predators. [24]

### Marine iguana body language

- Lying flat on the lava with its legs spread out: Basking: warming up after a swim in the cold sea. [6][1]
- Sneezing out a white spray: Normal: it is getting rid of extra salt after feeding. [1][21]
- A male bobbing his head: A territorial display: 'this patch of shore is mine'. [1][29]
- Two males pushing head to head: A fight over territory. Keep well back. [1]
- Head suddenly raised after a mockingbird calls: On alert: a hawk may be nearby. [8]

### Looks

- **Adult male**: Sooty black with a tall crest. Males are about twice as heavy as females and up to 1.33 m long. (Defends a patch of shore in the breeding season) [1][13]
- **Breeding male, Española**: On Española and Floreana, top males turn bright red with green or blue legs when breeding. Why is still unknown. (Shows off to females and rivals) [1]
- **Adult female**: Smaller, up to about 78.5 cm long, with a lower crest. Males have taller heads; females have longer heads. (Digs a nest burrow and lays 1–6 eggs) [1][19]
- **Juvenile**: Dark grey with a paler stripe down the middle of the back and only a tiny crest. (Feeds on rocks uncovered at low tide and hides in cracks) [2][1]

### Marine iguana quiz

1. What do adult marine iguanas mainly eat? **Red and green algae.** They graze on seaweed, scraping it off rocks above and below the water. [5][1]
2. How does a marine iguana get rid of extra salt? **It sneezes it out through its nose.** Glands in the nose pull salt out of the blood, and the iguana sneezes it out. [21][1]
3. What is the white crust often seen on a marine iguana's head? **Dried salt.** The salty spray it sneezes out lands on its head and dries white. [21]
4. What can happen to adult marine iguanas during an El Niño famine? **They get shorter.** Some shrank by up to 20% of their length and grew again when food came back. [3][4]
5. How does a marine iguana swim? **By swinging its flat tail and body from side to side.** It tucks its legs against its sides and wiggles its body and paddle-shaped tail. [6]
6. Which marine iguanas dive to feed in deep water? **Mostly the big ones.** Iguanas heavier than about 1.8 kg dive. Smaller ones graze on rocks at low tide. [1]
7. Why does a marine iguana bask on black lava after a swim? **To warm up after the cold sea.** The sea is cold, so it warms up in the sun. It heats up about twice as fast as it cools down. [11][1]
8. Which bird's alarm call do marine iguanas react to? **The Galápagos mockingbird's.** About 45% of iguanas went on alert to mockingbird alarm calls, but only about 28% to a mockingbird's normal song. [8]
9. What does 'Amblyrhynchus' mean? **Blunt snout.** It comes from Greek words for 'blunt' and 'snout'. [1]
10. How do hatchling marine iguanas get the microbes they need to digest algae? **By eating adult droppings.** Hatchlings eat adult droppings to pick up the gut microbes. [1][10]
11. On which island do breeding males turn red with green legs? **Española.** On Española and Floreana, top males turn red with green or blue legs in the breeding season. [1]
12. Who first called marine iguanas 'imps of darkness'? **A visitor whose words were printed in an earlier voyage book.** Darwin wrote 'Somebody calls them imps of darkness'. The phrase came from the earlier book about HMS Blonde. [7]

### Sources (checked 2026-10-29)

1. [Arteaga A, Guayasamin JM (2023). Marine Iguana (Amblyrhynchus cristatus). In: Arteaga A, Bustamante L, Vieira J (eds) Reptiles of Ecuador: Life in the middle of the world.](https://doi.org/10.47051/XNIC9736)
2. [Roy K (2000). Amblyrhynchus cristatus (marine iguana). Animal Diversity Web, University of Michigan Museum of Zoology.](https://animaldiversity.org/accounts/Amblyrhynchus_cristatus/)
3. [Wikelski M, Thom C (2000). Marine iguanas shrink to survive El Niño. Nature 403: 37–38.](https://doi.org/10.1038/47396)
4. [University of Illinois at Urbana-Champaign (2000). News release on Wikelski & Thom's study of shrinking marine iguanas, via ScienceDaily, 10 January 2000.](https://www.sciencedaily.com/releases/2000/01/000110071021.htm)
5. [Dubiner S, Muñoz-Pérez JP, Lewbart GA, Lohmann KJ, Hirschfeld M, Alarcón-Ruales D, Rivadeneira TCC, Loyola A, Meiri S, Levin E (2025). Marine iguanas have lower metabolic rates during El Niño. Journal of Experimental Biology 228(17): jeb250907.](https://pmc.ncbi.nlm.nih.gov/articles/PMC12450463/)
6. [Darwin C (1845). Journal of Researches into the Natural History and Geology of the Countries Visited during the Voyage of H.M.S. Beagle, 2nd edition, chapter XVII (Galápagos Archipelago). Project Gutenberg.](https://www.gutenberg.org/ebooks/944)
7. [Darwin C. Beagle Diary, entries for 17 September and 1 and 9 October 1835 (ed. N. Barlow), with editor's note on 'imps of darkness'. Transcription at galapagos.to.](https://galapagos.to/TEXTS/DIARY.HTM)
8. [Vitousek MN, Adelman JS, Gregory NC, Clair JJ (2007). Heterospecific alarm call recognition in a non-vocal reptile. Biology Letters 3(6): 632–634.](https://pmc.ncbi.nlm.nih.gov/articles/PMC2391237/)
9. [Vitousek MN, Mitchell MA, Woakes AJ, Niemack MD, Wikelski M (2007). High costs of female choice in a lekking lizard. PLoS ONE 2(6): e567.](https://doi.org/10.1371/journal.pone.0000567)
10. [Mackie RI, Rycyk M, Ruemmler RL, Aminov RI, Wikelski M (2004). Biochemical and microbiological evidence for fermentative digestion in free-living land iguanas (Conolophus pallidus) and marine iguanas (Amblyrhynchus cristatus) on the Galápagos archipelago. Physiological and Biochemical Zoology 77(1): 127–138.](https://doi.org/10.1086/383498)
11. [Bartholomew GA, Lasiewski RC (1965). Heating and cooling rates, heart rate and simulated diving in the Galapagos marine iguana. Comparative Biochemistry and Physiology 16: 573–582 (summary via the IUCN Iguana Specialist Group library).](https://library.iucn-isg.org/biblio_display_info.php?id=3335&q=)
12. [Butler PJ, Frappell PB, Wang T, Wikelski M (2002). The relationship between heart rate and rate of oxygen consumption in Galapagos marine iguanas (Amblyrhynchus cristatus) at two different temperatures. Journal of Experimental Biology 205(13): 1917–1924.](https://doi.org/10.1242/jeb.205.13.1917)
13. [Wikelski M, Trillmich F (1997). Body size and sexual size dimorphism in marine iguanas fluctuate as a result of opposing natural and sexual selection: an island comparison. Evolution 51(3): 922–936.](https://doi.org/10.1111/j.1558-5646.1997.tb03673.x)
14. [Wikelski M, Nelson K (2004). Conservation of Galápagos marine iguanas (Amblyrhynchus cristatus). Iguana 11(4): 190–197.](https://kops.uni-konstanz.de/entities/publication/3ff96bdc-b257-439a-9d69-28f18d55eb3b)
15. [Steinfartz S, Glaberman S, Lanterbecq D, Marquez C, Rassmann K, Caccone A (2007). Genetic impact of a severe El Niño event on Galápagos marine iguanas (Amblyrhynchus cristatus). PLoS ONE 2(12): e1285.](https://doi.org/10.1371/journal.pone.0001285)
16. [Wikelski M, Wong V, Chevalier B, Rattenborg N, Snell HL (2002). Marine iguanas die from trace oil pollution. Nature 417: 607–608.](https://doi.org/10.1038/417607a)
17. [EurekAlert! (2002). News release on Wikelski and colleagues' study of marine iguana deaths on Santa Fé after the 2001 oil spill.](https://www.eurekalert.org/news-releases/561127)
18. [Miralles A, Macleod A, Rodríguez A, Ibáñez A, Jiménez-Uzcategui G, Quezada G, Vences M, Steinfartz S (2017). Shedding light on the Imps of Darkness: an integrative taxonomic revision of the Galápagos marine iguanas (genus Amblyrhynchus). Zoological Journal of the Linnean Society 181(3): 678–710.](https://doi.org/10.1093/zoolinnean/zlx007)
19. [Chiari Y, Glaberman S, Tarroso P, Caccone A, Claude J (2016). Ecological and evolutionary influences on body size and shape in the Galápagos marine iguana (Amblyrhynchus cristatus). Oecologia 181(3): 885–894.](https://doi.org/10.1007/s00442-016-3618-1)
20. [Schmidt-Nielsen K, Fange R (1958). Salt glands in marine reptiles. Nature 182: 783–785.](https://doi.org/10.1038/182783a0)
21. [Stegman R (2020). Meet the Ocean Salt Baes: Marine Iguanas. Ocean Conservancy, 23 January 2020.](https://oceanconservancy.org/?p=49085)
22. [GBIF. Amblyrhynchus cristatus Bell, 1825 (IUCN Red List category: Vulnerable).](https://www.gbif.org/species/5224602)
23. [Paparella I, Caldwell MW (2022). Cranial anatomy of the Galápagos marine iguana Amblyrhynchus cristatus (Squamata: Iguanidae). The Anatomical Record 305(7): 1739–1786.](https://doi.org/10.1002/ar.24797)
24. [Arteaga A, Guayasamin JM (2023). Galápagos Land-Iguana (Conolophus subcristatus). In: Arteaga A, Bustamante L, Vieira J (eds) Reptiles of Ecuador: Life in the middle of the world.](https://doi.org/10.47051/CAND9772)
25. [Gingell F (2005). Iguana iguana (green iguana). Animal Diversity Web, University of Michigan Museum of Zoology.](https://animaldiversity.org/accounts/Iguana_iguana/)
26. [Borcyk J, Fortner A, Claunch NM, Johnson SA (2021, reviewed 2024). Florida's Introduced Reptiles: Green Iguana (Iguana iguana). UF/IFAS Extension, WEC440.](https://edis.ifas.ufl.edu/publication/UW485)
27. [GBIF. Iguana iguana (Linnaeus, 1758) (IUCN Red List category: Least Concern).](https://www.gbif.org/species/2459658)
29. [Ibáñez A, Menke M, Quezada G, Jiménez-Uzcátegui G, Schulz S, Steinfartz S (2017). Diversity of compounds in femoral secretions of Galápagos iguanas (genera: Amblyrhynchus and Conolophus), and their potential role in sexual communication in lek-mating marine iguanas (Amblyrhynchus cristatus). PeerJ 5: e3689.](https://doi.org/10.7717/peerj.3689)
30. [MacLeod A, Rodríguez A, Vences M, Orozco-terWengel P, García C, Trillmich F, Gentile G, Caccone A, Quezada G, Steinfartz S (2015). Hybridization masks speciation in the evolutionary history of the Galápagos marine iguana. Proceedings of the Royal Society B 282(1809): 20150425.](https://doi.org/10.1098/rspb.2015.0425)

## Measurements & details

- **Length:** 50-130 cm
- **Weight:** 0.5-10 kg
- **Lifespan:** 10-20 years
- **Speed:** 12 km/h
- **Swim Speed:** 15 km/h
- **Clutch Size:** 1-4
- **Incubation:** 90-120 days
- **Maximum Depth:** 15 m

## Diet & Feeding

They are vegetarians of the sea, primarily munching on algae scraped from underwater rocks.

- **Primary Foods:** red algae, green algae, seaweed
- **Foraging Method:** Grazing

## Ecological connections

- **Eaten by:** Galápagos Hawk (*Buteo galapagoensis*) — Hunts adults and juveniles.
- **Eaten by:** Lava Heron (*Butorides sundevalli*) — Preys on hatchlings and small juveniles.
- **Eaten by:** [Domestic Cat](https://www.snappit.app/explore/domestic-cat) (*Felis catus*) — Introduced predator hunting juveniles.

## Traits

- [Wildlife](https://www.snappit.app/explore/traits/wildlife): Wildlife encompasses all undomesticated animal and plant life existing in their natural habitats.
- [Herbivorous](https://www.snappit.app/explore/traits/herbivorous): This trait characterizes organisms whose diet consists entirely or primarily of plant material.
- [Thermoregulating](https://www.snappit.app/explore/traits/thermoregulating): Thermoregulating organisms maintain a stable internal body temperature despite fluctuations in the external environment.
- [Volcanic](https://www.snappit.app/explore/traits/volcanic): This habitat trait describes species found in volcanic regions, including areas with recent lava flows, volcanic ash, or on volcanic islands, often characterized by unique soil compositions.
- [Spiky/Thorny](https://www.snappit.app/explore/traits/spiky-thorny): Possessing sharp, pointed projections or spines on the body or surface.
- [Coastal](https://www.snappit.app/explore/traits/coastal): Coastal habitats are dynamic environments located along the interface between land and sea, influenced by tides, waves, and saltwater.
- [Diurnal](https://www.snappit.app/explore/traits/diurnal): Diurnal animals are primarily active during daylight hours, typically resting or sleeping at night.
- [Marine](https://www.snappit.app/explore/traits/marine): Marine habitats encompass all saltwater environments of the Earth's oceans, supporting an immense diversity of aquatic life.

## Collections

- [Reptiles](https://www.snappit.app/explore/collections/reptiles)

## Safety

**Danger:** 1/5 · Very low

Do not disturb marine iguanas in their natural habitat to keep them safe.

## Frequently Asked Questions

### How to identify Galápagos Marine Iguana?

Compare toes, scales, head shape, crests and tail proportions. Many lizards can drop and regrow their tails, so a short tail isn't always a species trait. Lizard Identifier: upload a photo and compare the visible details.

### How long is Galápagos Marine Iguana?

50-130 cm

### How much does Galápagos Marine Iguana weigh?

0.5-10 kg

### How long does Galápagos Marine Iguana live?

10-20 years

### How fast can Galápagos Marine Iguana move?

12 km/h

### What does Galápagos Marine Iguana eat?

They are vegetarians of the sea, primarily munching on algae scraped from underwater rocks.

### How fast can Galápagos Marine Iguana swim?

15 km/h

### Where is Galápagos Marine Iguana usually found?

Coastal areas

## More Reptiles

- [Pond Slider](https://www.snappit.app/explore/pond-slider) (*Trachemys scripta*)
- [Western Fence Lizard](https://www.snappit.app/explore/western-fence-lizard) (*Sceloporus occidentalis*)
- [Common Five-lined Skink](https://www.snappit.app/explore/common-five-lined-skink) (*Plestiodon fasciatus*)
- [Desert Spiny Lizard](https://www.snappit.app/explore/desert-spiny-lizard) (*Sceloporus magister*)

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Source: [Galápagos Marine Iguana: Facts & Places to See — Snappit](https://www.snappit.app/explore/gal-pagos-marine-iguana)