About the Marine Iguana

Marine iguanas (Amblyrhynchus cristatus) are large reptiles found exclusively in the Galápagos Islands, hence them often being referred to as Galápagos Iguanas. They are the only lizard species capable of foraging in the ocean, utilising their robust bodies and  dark, often black colouration, that helps them absorb heat after swimming in the cold ocean. Males are generally larger, reaching up to 1.5 meters (5 feet) in length, while females are smaller.

These iguanas are herbivorous, primarily feeding on algae. They have special adaptations such as flattened tails for swimming and strong, sharp claws to help them cling to rocks in strong currents. They are often seen basking in the sun on rocky shores to regulate their body temperature after feeding in the chilly waters, which is a not an uncommon photo opportunity for travellers, and they are social animals that often dwell in large colonies.

Expedition guided excursions will be led by knowledgeable and local naturalists who provide insights into the behavior and ecology of the iguanas and their unique environment. 

The Galápagos Islands are a UNESCO World Heritage site, and marine iguanas are protected under Ecuadorian law. The Galápagos National Park and Marine Reserve ensure the conservation of their habitats.  Ongoing research and monitoring efforts help understand the impacts of climate change and human activities on marine iguana populations. Conservation programs focus on habitat protection and invasive species control.

Activities to see Marine Iguanas

Istock 1059413880 Kunhui Chih Galapagos Ignuana Marine Snorkelling 298
Marine Iguana diving in the Galapagos

Snorkelling, if offered by the expedition company, us one of the best options to see marine iguanas feeding on algae. The aquatic perspective allows for a close-up view of their aforementioned foraging behavior.

Land hikes along the coast al areas where marine iguanas bask are also an option, where your expedition guides and naturalists can explain the iguanas ecological role and the adaptations that enable their unique marine lifestyle.

Marine iguanas are relatively common within the Galápagos Islands, where they are endemic. These islands are home to 11 recognized subspecies of marine iguanas, with populations found on almost every island within the archipelago. The total population is estimated to be around 250,000 individuals.

Feral dogs, cats, and rats introduced to the islands pose significant threats, especially to eggs and juvenile iguanas. These invasive species prey on young iguanas, reducing their survival rates.

Human activities such as construction, tourism, and pollution can disrupt their natural habitats. Coastal development and marine pollution are particularly detrimental, affecting both their terrestrial basking sites and underwater feeding grounds​and the introduction of new diseases by humans and domestic animals can have severe impacts on marine iguana populations, which have no natural immunity to these pathogens​.

Climate change is a continued threat to Marine Iguanas. Higher sea levels can lead to the loss of nesting beaches and foraging areas, essential for their survival.

Marine iguanas also rely on external temperatures to regulate their body heat. Increasing temperatures can disrupt their thermoregulation processes, affecting their ability to forage and digest food efficiently. Changes in ocean chemistry can also affect the availability and quality of algae, their primary food source. Ocean acidification, driven by increased CO2 levels, can impact the growth and composition of algal communities, potentially leading to food shortages​.

More frequent and severe El Niño events, associated with climate change, can also reduce the availability of algae due to warmer sea temperatures. 

Where to see Marine Iguanas

Marine Iguanas and endemic to the Galápagos Islands meaning expedition and small-ship adventure cruising is one of the best ways to see them. Most Galápagos cruises visit islands such as Isabela, Fernandina, and Española, where marine iguanas are most commonly found. These islands offer rocky shorelines and intertidal zones ideal for iguana sightings.

Interesting facts about Marine Iguanas

One of the most unusual aspects of marine iguanas is their ability to expel excess salt from their bodies. Due to their algae diet, they ingest a significant amount of saltwater, which could be harmful if not regulated. To manage this, marine iguanas have developed specialized salt glands located near their nostrils. These glands efficiently filter the salt from their bloodstream and allow the iguanas to expel it by sneezing.

You've probably seen the photos. After feeding in the cold ocean, marine iguanas need to bask in the sun to raise their body temperature. Their dark coloration helps them absorb heat more efficiently. This thermoregulation is essential for their digestion and overall metabolic processes​

Julie L. Kessler

Iguanas Galapagos Julie L Kessler

Related Stories & Guides