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Marine Iguana

The marine iguana is the only lizard in the world that forages in the ocean — a remarkable trait that makes it one of the most unique reptiles on the planet. Found only in the Galápagos Islands, these expert swimmers are thought to have diverged from land iguanas at least 10 million years ago.

 

On average, marine iguanas are about 26 centimeters (10.2 inches) long, although males are significantly larger than females. They feed almost exclusively on marine algae, with smaller individuals grazing on exposed algae between tides while larger iguanas dive up to 30 meters (98 feet) deep to reach algal beds beneath the waves. Their wide heads, blunt snouts, and sharp claws benefit their ability to graze underwater, while their flattened tail helps them swim through the waves. 

Feeding in or near cold ocean water can be a challenge for lizards, since they cannot regulate their own body temperature. To warm up after a chilly swim, marine iguanas will bask in the sunlight to warm up, with their dark coloring aiding in soaking up rays. They have also evolved some fascinating adaptations to survive in this coastal environment, including the ability to excrete salt consumed from seawater through specialized glands in their noses.

 

 

Marine iguanas face a number of threats. El Niño events, which warm ocean waters and reduce algal growth, can lead to food shortages and mass die-offs. It is predicted that climate change may increase the frequency and intensity of these events, which could put the future of some populations of marine iguanas at serious risk. They are also highly vulnerable to predators like cats, dogs, and rats, which prey on eggs and hatchlings. Impacts from increased tourism to the Galápagos, including pollution and habitat degradation, further threaten their survival.  

 

 

Protecting marine iguanas means protecting the Galápagos. Responsible tourism, invasive species control, and enhanced protections are key to ensuring the future of this species, as well as combatting the climate crisis. Oceana campaigns to stop the expansion of offshore drilling, as science tells us this has the potential to reduce greenhouse gas emissions more than any other ocean-based solution. Learn more about our campaign to protect our climate here.

 

 

  • Animal Diversity Web 
  • IUCN Red List 
  • Berry, K. A., Muñoz-Pérez, J. P., Vintimilla-Palacios, C. P., & Clemente, C. J. (2020). The mystery of a marine monster: Morphological and performance modifications in the world’s only marine lizard, the Galápagos marine iguana (Amblyrhynchus cristatus). Biological Journal of the Linnean Society, 133(1), 68–80. https://doi.org/10.1101/2020.05.16.099184 
  • Tracy, R., & Christian, K. A. (1985). Are marine iguana tails flattened? (short note). British Journal of Herpetology, 6, 434-435.  
  • Wikelski, M., & Trillmich, F. (1994). Foraging strategies of the Galapagos marine iguana (Amblyrhynchus cristatus) : Adapting behavioral rules to ontogenetic size change. Behaviour, 128(3–4), 255–279. https://doi.org/10.1163/156853994×00280 

 

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