What Do Marine Iguanas Eat?

Learn about the fascinating feeding habits of the enigmatic marine iguanas - the ocean’s only lizard.

Nov 13, 2023By Caitlin Ross
what do marine iguanas eat

The intriguing marine iguana has an interesting diet and even more interesting behavioral patterns that result from their choice of food. Differing drastically from the regular iguana you’re familiar with, this lizardhas adapted to a lifestyle in the ocean and has chosen to dine in the deep - here’s everything you need to know about their feeding habits.

What Are Marine Iguanas?

marine iguana sunbathing
Image credit: Wikipedia

First, you might be wondering what exactly a marine iguana is in the first place. These creatures are one of the very few marine reptiles and the only lizard in the world that has adapted to a marine environment.

Sea iguanas are found exclusively in the Galapagos Islands and are known for their ability to feed in shallow marine waters. These reptiles are excellent swimmers and can dive more than 65 feet underwater - staying under the surface for up to 30 minutes at a time.

However, despite these aquatic abilities, they prefer to spend most of their time on the shore and often need to bake themselves in the sun for hours to warm up after time spent in the icy water.

What Do They Eat?

algae on rocks
Image credit: 123RF

One of the many ways in which these reptiles have adapted to an island lifestyle is in their diet and feeding habits. Marine iguanas are unique in that they feed predominantly on the algae that grows on rocks near the shores of the Galapagos Islands.

There are nine different types of algae that the iguanas feed on - and they have been noted to prefer the red and green inter and subtidal algae, of which there are 4 or 5 different species. However, they will supplement their diets with other algae species and even seaweed when they can’t find their usual favorite dish.

The iguanas struggle to digest brown algae, and it can even be toxic to them. Warmer water causes a decrease in red and green algae and an increase in brown - which can lead to a serious threat to the marine iguana population during periodic El Niño events.

How Do They Get Their Food?

marine iguana eating
Image credit: bioGraphic

But how do the iguanas feed on the algae? This is where their incredible swimming skills (and other adaptations) come into play!

First of all, these reptiles can dive incredibly deep in the water to forage for food and find the best algae. Stronger iguanas can even swim out into the tides, using their strong and sharp claws to cling to the rocks. However, most of the iguanas stay closer to the shore and feed in shallow waters to avoid the cold and the strong water currents.

The lizards have blunt noses and razor-sharp teeth that allow them to easily scrape algae off the rocks in the water.

What About All the Salt?

marine iguana sneezing
Image credit: X

Feeding underwater means that these lizards are ingesting a lot of seawater and, by default, a whole lot of salt, which can cause dehydration.

As you might have guessed, this amount of sodium can cause dehydration and even damage to the lizards’ kidneys. This is why they have evolved salt glands. Marine iguanas are famous for their salt-sneezing habits - the salt glands force excess salt out of the creature’s nostrils at a rapid pace, spraying salt and seawater everywhere in a dramatic display that tourists love.

The lizard’s cranium has an exceptionally large nasal cavity to accommodate all the salt before it is unceremoniously sneezed out. After the big sneeze, salt crystals tend to leave a white crown on the iguanas’ heads, making them the unofficial kings of the islands.

Do They Eat Anything Else?

marine iguana and bird
Image credit: Galapagos Conservation Trust

A life of eating nothing but algae sound… Pretty boring. But the marine iguanas are perfectly happy with their slimy diets.

On rare occasions, when their usual food is scarce, these lizards may also feed on crustaceans, insects, sea lion feces, and even after birth! They might also munch on the droppings of other iguanas or red crabs - clearly, these are nutritious options. But keep in mind that these deviations are rare, and the marine iguanas typically stick to feeding from the rocks as long as the right types of algae are available and abundant.

How Are They Different from Land Iguanas?

land iguana
Image credit: Forest Wildlife

While marine iguanas and land iguanas are both herbivorous creatures, their diets are still remarkably different.

Naturally, you won’t find a land iguana munching on algae in your swimming pool! These land lizards typically feed on foliage, flowers, and fruit. However, despite being predominantly herbivores, iguanas will occasionally eat more than just plants - dabbling in delicacies like insects, smaller lizards, and other tiny animals, and eggs, although this is relatively uncommon.

Iguanas kept as pets are typically fed dark green veggies and some fruits, but out in the wild, their diets can differ quite significantly depending on what type of iguana it is.

Caitlin Ross
By Caitlin Ross

Caitlin is an animal lover at heart with a passion for writing and sharing this love with the world. She’s a born and raised South African and grew up always surrounded by animals: more pets than she can count, and regularly adventuring with her family into the bush, where she feels most at peace with the wildlife in their natural habitat.