Marine Iguana

Reptiles of Ecuador | Sauria | Iguanidae | Amblyrhynchus cristatus

Spanish common name. Iguana marina.

Recognition. ♂♂ 1330 mm ♀♀ 785 mm. Amblyrhynchus cristatus is one of four species of iguanas occurring on the Galapagos islands. The other three are the land iguanas of the genus Conolophus. The Marine Iguana differs from all of them by having a blunt snount and a laterally compressed tail.

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Adult male.

Adult male of Amblyrhynchus cristatus

Picture. Subadult male.

Subadult male of Amblyrhynchus cristatus

Picture. Subadult male.

Subadult male of Amblyrhynchus cristatus

Picture. Subadult male.

Subadult male of Amblyrhynchus cristatus

Picture. Subadult male.

Subadult male of Amblyrhynchus cristatus

Picture. Subadult male.

Subadult male of Amblyrhynchus cristatus

Picture. Subadult male.

Subadult male of Amblyrhynchus cristatus

Picture. Subadult male.

Subadult male of Amblyrhynchus cristatus

Picture. Subadult male.

Subadult male of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Adult female.

Adult female of Amblyrhynchus cristatus

Picture. Juvenile.

Juvenile of Amblyrhynchus cristatus

Picture. Juvenile.

Juvenile of Amblyrhynchus cristatus

Picture. Juvenile.

Juvenile of Amblyrhynchus cristatus

Natural history. Extremely common. Amblyrhynchus cristatus is a diurnal and gregarious denizen of coastal volcanic outcrops, mangroves and sandy beaches1. It is a mostly terrestrial species that spends nearly 5% of a 24 h day in the water, grazing seaweed of the surface of rocks2. The Marine Iguana supplements its diet with beach plants3, grasshoppers, cockroaches, crustaceans or even sea lion feces and afterbirth4. Hatchlings feed on the adult’s feces to obtain the gut microorganisms needed for the digestion of algae5. Big Marine Iguanas (heavier than 1,800 g) dive for up to 20 minutes and up to 15 m deep to feed1,2, whereas smaller ones (lighter than 1,200 g) forage on exposed intertidal rocks2. After a dive, the Marine Iguana “sneezes” excess salt1. Amblyrhynchus cristatus spends the first hours after sunrise basking1, and usually moves into the sea between 7h30 and 8h001. During hot afternoons, it seeks the shade of reef crevices, large boulders, mangroves, and shrubs1. Just before sunset, it retreats into these same hideouts, but it can also spend the night exposed on the reef1 or up on the mangroves6. Predators include hawks, owls, gulls, herons, cats, dogs, pigs, rats, snakes (P. biserialis, P. dorsalis, and P. occidentalis), hawkfish, and crabs1,79. As defense mechanism, A. cristatus runs into crevices10. Breeding season starts in Dec–Jan1. About month later, females, which compete fiercely over nesting sites11, dig 30–40 cm holes in sandy soil11 and lay 1–6 eggs7 that take 89–120 days to hatch6. Mockingbirds prey upon eggs11. In some islands, males of the Marine Iguana keep harems and defend territories by bobbing their heads, or fighting head to head with intruders1. Amblyrhynchus cristatus is known to hybridize with Conolophus subcristatus12. This species can live up to 30 years13.

Conservation. Vulnerable14. Amblyrhynchus cristatus is listed in this category because, although it occurs in aggregations of thousands of individuals15, its extent of occurrence is estimated to be less than 5,000 km2, it experiences periodic population declines of up to 85% mortality due to El Niño events, and is threatened by pollution and invasive predators14.

Distribution. Coastal areas of all major islands and most of their surrounding islets in Galapagos, Ecuador.

Distribution of Amblyrhynchus cristatus

Etymology. The generic name Amblyrhynchus, which comes from the Greek words amblys (meaning “obtuse”) and rhynchos (meaning “snout”)16, is a reference to the blunt snout of the Marine Iguana. The specific epithet cristatus, which comes from the Latin word crista (meaning “ridge”) and the suffix atus (meaning “provided with”)16, refers to the crest of enlarged dorsal scales of the Marine Iguana10.

See it in the wild. Although the Marine Iguana can be seen year-round on almost any rocky beach in Galapagos, the best time to photograph it is during the peak of the breeding season (Jan–Feb), when males are strikingly colored. Amblyrhynchus cristatus can be seen with a 100% certainty on the 100 species herping tour.

Authors. Alejandro Arteaga

Photographers. Jose Vieira and Alejandro Arteaga.

How to cite? Arteaga A (2019) Amblyrhynchus cristatus. In: Arteaga A, Bustamante L, Guayasamin JM (Eds) Reptiles of Ecuador. Available from: www.tropicalherping.com

Literature cited.

1. Carpenter C (1966) The marine iguana of the Galapagos Islands, its behavior and physiology. Proceedings of the California Academy of Sciences 34: 329–376.

2. Trillmich KGK, Trillmich F (1986) Foraging strategies of the Marine Iguana, Amblyrhynchus cristatus. Behavior, Ecology and Sociobiology 18: 259–266.

3. Vitousek MN, Rubenstein DR, Wikelski M (2007) The evolution of foraging behavior in the Galápagos marine iguana: natural and sexual selection on body size drives ecological, morphological, and behavioral specialization. In: Reilly SM, McBrayer LD, Miles DB (Eds) Lizard ecology: the evolutionary consequences of foraging mode. Cambridge University Press, New York, 491–507.

4. Wikelski M, Wrege PH (2000) Niche expansion, body size, and survival in Galápagos marine iguanas. Oecologia 124: 107–115.

5. Rubenstein DR, Wikelski M (2003) Seasonal changes in food quality: a proximate cue for reproductive timing in marine iguanas. Ecology 84: 3013–3023.

6. Eibl-Eibesfeldt I (1984) The large iguanas of the Galápagos Islands. In: Perry R (Ed) Key environments: Galápagos. Pergamon Press, Oxford, 157–173.

7. Laurie WA, Brown D (1990) Population biology of marine iguanas (Amblyrhynchus cristatus). II. Changes in annual survival rates and the effects of size, sex, age and fecundity in a population crash. Journal of Animal Ecology 59: 529–544.

8. Laurie WA (1983) Marine iguanas in Galapagos. Oryx 17: 18–25.

9. Christian EJ (2017) Demography and conservation of the Floreana racer (Pseudalsophis biserialis biserialis) on Gardner-by-Floreana and Champion islets, Galápagos islands, Ecuador. PhD thesis, Auckland, New Zealand: Massey University.

10. Van Denburgh J, Slevin JR (1913) Expedition of the California Academy of Sciences to the Galapagos Islands, 1905-1906. IX. The Galapagoan lizards of the genus Tropidurus with notes on iguanas of the genera Conolophus and Amblyrhynchus. Proceedings of the California Academy of Sciences 2: 132–202.

11. Eibl-Eibesfeldt I (1966) Das Verteidigen der Eiablageplätze bei der Hood‐Meerechse. Zeitschrift für Tierpsychologie 23: 627–631.

12. Rassmann K, Trillmich F, Tautz D (1997) Hybridization between the Galapagos land and marine iguana (Conolophus subcristatus and Amblyrhynchus cristatus) on Plaza Sur. Journal of Zoology 242: 729–739.

13. Berry RJ (1984) Evolution in the Galapagos Islands. Academic Press, London, 270 pp.

14. Nelson K, Snell H, Wikelski M (2004) Amblyrhynchus cristatus. The IUCN red list of threatened species. Available from: http://www.iucnredlist.org

15. Bowman RI, Berson M, Leviton AE (1983) Patterns of evolution in Galapagos organisms. Pacific Division, AAAS, San Francisco, 568 pp.

16. Brown RW (1956) Composition of scientic words. Smithsonian Books, Washington, 882 pp.