The Nature LibraryEN·ES
NL·0498AnimalsIguanidaeReptile11,119 field observations
Marine iguanaNL·0498
Plate 1 of 8. (c) Simon Pierce, some rights reserved (CC BY-NC), uploaded by Simon Pierce · via iNaturalist

Herbarium of the Nature Library

Name
Amblyrhynchus cristatus
Family
Iguanidae
Native to
Galápagos Islands, Ecuador
Habitat
Rocky shore, Intertidal zone, Subtidal reef
IUCN VU · Vulnerable

Marine iguana

Amblyrhynchus cristatus

Also calledIguana marina (Spanish) · Sea iguana

The only lizard in the world that forages in the sea. On the Galápagos Islands it dives into cold surf to graze algae, then warms up on black lava rocks. Charles Darwin recorded that they had been called 'imps of darkness'.

The marine iguana, also known as the sea iguana, saltwater iguana, or Galápagos marine iguana, is a species of iguana found only on the Galápagos Islands (Ecuador). Unique among modern lizards, it is a marine reptile that has the ability to forage in the sea for algae, which make up almost all of its diet. Marine iguanas are the only extant lizard that spends time in a marine environment. Large males are able to dive to find this food source, while females and smaller males feed during low tide in the intertidal zone. They mainly live in colonies on rocky shores where they bask after visiting the relatively cold water or intertidal zone, but can also be seen in marshes, mangrove swamps and beaches. Large males defend territories for a short period, but smaller males have other breeding strategies. After mating, the female digs a nest hole in the soil where she lays her eggs, leaving them to hatch on their own a few months later. Wikipedia

§1

What it can do

  1. iDives to over 10 m and grazes algae on rocks with its short blunt snout
  2. iiSneezes out excess salt from glands near its nose
  3. iiiShrinks its body, even its bones, when food is short in El Niño years, then grows again
  4. ivDigests seaweed with the help of gut microbes
§2

In the field

Field marks

  • aShort, blunt snout and spiny crest along the back
  • bBlack or grey body; on some islands males are mottled red and green in the breeding season
  • cFlattened tail for swimming
  • dOften white-crusted head from sneezed salt
Not to be confused with
Galápagos land iguanas (Conolophus) are yellow-brown with a long rounded tail and live inland. Lava lizards (Microlophus) are much smaller.
Where to see it
All main Galápagos islands; Española (Punta Suárez) for red-green males, Fernandina (Punta Espinoza) for large colonies
When
Resident; breeding coloration and mating December–January on many islands
§3

Life & habits

Diet
Red and green algae from intertidal and subtidal rocks
Habitat
Rocky lava coasts and nearby water
Size
Up to ~1.3 m including tail; males larger
Lifespan
~12 years or more

Large males dive offshore, while females and smaller iguanas graze on algae exposed at low tide. They pile together on rocks at night to keep warm.

§4

Where it lives

Recorded sightings

—

geo-referenced records in GBIF, from museums, herbaria and field observers.

Native range

Galápagos Islands, Ecuador

Drag the globe to turn it. Dots are where records exist, not a range map; darker means more records.

§5

In the old herbals & bestiaries

No plate in the Source Library names this exact species, so these show its closest relatives as the old naturalists drew them: same genus, or the same kind of animal. Click a plate to read the page it came from, with translation.

§6

In the stacks

Searching the stacks…

Every page naming Amblyrhynchus cristatus in the Biodiversity Heritage Library →

§7

Marginalia

Darwin wrote in 1835 that marine iguanas were 'hideous-looking' and 'most disgusting, clumsy lizards', and noted that 'somebody calls them imps of darkness', a phrase used earlier by Lord Byron's 1826 voyage account. He threw one into the sea repeatedly to watch it swim back.

Curiosity

In El Niño years marine iguanas can shrink by up to ~20% in length, and their bones get shorter, then they regrow when food returns.

§8

Kinship

  1. kingdomAnimalia
  2. ›phylumChordata
  3. ›subphylumVertebrata
  4. ›classReptilia
  5. ›orderSquamata
  6. ›suborderSauria
  7. ›infraorderIguania
  8. ›parvorderPleurodonta
  9. ›familyIguanidae
  10. ›genusAmblyrhynchus
Open its branch on the Wheel of Life →

Fact-checked: 2 corrections made to this sheet. Photographs: iNaturalist contributors under the licences shown. Records: GBIF.org. Historical plates: Source Library (CC BY-SA 4.0; originals public domain). Summary text: Nature Library editors and Wikipedia (CC BY-SA). Medicinal and edibility notes are historical and educational, not advice. iNaturalist taxon 35347.