5 Interesting Facts About the Marine Iguana

A marvel of evolution, let’s take a deep dive into the underwater world of the marine iguana!

Sep 2, 2023By Lauren Rey
facts marine iguana

One of the most unique and beloved creatures of the Galapagos Islands, the marine iguana has been fascinating biologists since the days of Charles Darwin. Biologists believe the marine iguana evolved from land iguanas around 4.5 million years ago. Through the development of several unique adaptations that land iguanas do not possess, marine iguanas have been not only able to survive but thrive in their island habitats. Here’s a look at some fun facts about these mystifying marine reptiles!

5. They Are a Fascinating Tale of Evolution

marine iguana
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A fascinating species, adapted to both land and sea, the marine iguana is an extraordinary product of evolution. In fact, they were notably studied by the “father of evolution” himself, Charles Darwin.

With an impressive set of adaptations for life on the rocky shoreline, the marine iguana is unlike any other lizard species in the world. Marine iguanas are excellent swimmers, thanks in part to their flattened tails that help them glide through the water like crocodiles. They can also hold their breath for long periods of time and have specialized glands to process saltwater.

While they may appear fierce, marine iguanas are herbivores and are not considered dangerous to humans. They feed almost exclusively on algae. A marine iguana's long, sharp claws are to help them grip the rocks while they forage underwater. While their sharp teeth assist with scraping algae off the rocks. These features also help scare off would-be predators.

4. Marine Iguanas Are Found Only in One Place on Earth

marine iguanas galapagos
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While there are 35 species of iguanas found around the world, mostly in tropical and desert regions, marine iguanas are only found in one place — the Galapagos Islands. This archipelago off the coast of Ecuador has been their home for millions of years. They are even sometimes referred to as Galapagos marine iguanas.

Due to the isolation that comes with island living, there are almost a dozen subspecies with slightly different characteristics found on different islands. Each subspecies is uniquely adapted to its particular environment. Everything from weather patterns to food availability to local predators has affected the characteristics of each subspecies.

The marine iguanas found on the islands of Isabela and Fernandina are known to be the largest due to the abundance and nutrient density of the local algae. On the smaller, more southern islands, the most colorful iguanas are found. Nicknamed the “Christmas iguanas,” the marine iguanas of Española and Floreana islands can be bright red and green due to the nutrients found in the algae there.

3. They’re the Only Sea-Dwelling Lizards in the World

marine iguana swimming
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Uniquely adapted to ocean life, marine iguanas are the only sea-dwelling lizards in the world! While iguana populations in other regions can spend time in and around the ocean, marine iguanas spend their entire lives there. They are completely dependent on the ocean.

When not swimming and foraging for algae, marine iguanas will bask along the rocks to retain heat. They also mate and nest around the shoreline. They rarely, if ever, leave the comfort of their rocky enclaves. Marine iguanas are truly one of the most unique lizards in the world!

2. They Sneeze Salt

marine iguana sneezing salt
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One of the marine iguanas' most fascinating adaptations is not only their ability to process saltwater, but how they do it! Unlike other iguana species, the marine iguana has specialized glands that help them filter salt from their bodies. These glands release excess saline through the nostrils in what is known as a “salt sneeze.”

During their time underwater foraging for algae, marine iguanas ingest heavy amounts of salt. Once they return to the surface, their body will begin the process of filtering out excess salt through their exocrine glands, located in the nostrils.

Since marine iguanas are typically found in colonies, it’s not uncommon to see dozens of them piled atop each other, shooting salt from their nostrils in an almost synchronized display of evolutionary greatness. A favorite sight among tourists to the Galapagos Islands!

1. Marine Iguanas Can Dive to Extraordinary Depths

marine iguana eating algae
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Another impressive feat of the marine iguana is its ability to dive to great depths in search of food. These sea-faring lizards can dive more than 65 feet below the surface and hold their breath for up to 30 minutes while they scour the rocky ocean floor for algae. While other species of iguanas can swim, no other lizard species can dive to such depths!

To prepare for long dives, the marine iguana will bask in the sun for extended periods of time to raise their body temperature. Once they enter the water, they begin losing body heat. After diving, they will return to a basking state in order to bring their body heat back up again. They may continue this cycle of basking and diving until they’ve had their fill of algae for the day.

Lauren Rey
By Lauren Rey

A lover of all animals, Lauren’s background is in the veterinary world, but she is now a content writer on travel, wildlife, and all things pets! She’s based in Florida, but when not writing, she’s usually plotting out a new road trip route with her partner-in-crime. Pickles is a mixed-breed rescue dog that loves hiking, road trips, and Starbucks just as much as her mom does!