What Is Unique About The Marine Iguana

Do you love reptiles and lizards?

If so, you’re in the right place!

Today we’re uncovering one of the most unique and special lizards to walk the face of the earth.

They’re called the marine iguana, and if you’ve ever heard of this creature and wondered what is unique about the marine iguana, keep reading to find out!

The marine iguana has many unique characteristics, including their habitat, what and how they eat, and their body’s highly adaptive features. Still, they are most famous for being the only known marine (sea-going) reptile on earth.

Marine Iguana’s Habitat 

Marine iguanas are unlike most other iguana species because they only live in one specific place—the Galapagos Islands.

Marine iguanas are found living on every island in the Galapagos.

Because each island’s population of marine iguanas has been isolated for so long from the other islands’ populations of marine iguanas, there are now different subspecies on each island.

The varying subspecies of marine iguanas all boast slightly different shapes, colors, and sizes.

Marine Iguana’s Diet

Marine iguanas, much like other iguana species, are herbivores, meaning they primarily eat plants.

However, unlike other iguana species, marine iguanas subsist on a diet of marine algae and seaweed.

There are nine different species of algae identified as marine iguana food, although marine iguanas tend to prefer just 4-5 different species of red algae.

The algae grow along the rocky shores of the Galapagos Islands, meaning marine iguanas forage in the sea for their food (more on this later). 

While marine iguanas are primarily seaweed and algae-eating herbivores, they are highly adaptive creatures.

In times of food shortages, they have been known to eat crustaceans, grasshoppers, sea lion after birth, and even feces!

Marine Iguana’s Feeding Method

Another characteristic setting marine iguanas apart from all other iguanas (and all other lizard species) are their method of foraging for food in the sea.

We’ve already learned marine iguanas eat algae and seaweed growing in the ocean, but how do they (a primarily land-dwelling species) manage to swim, dive, and eat in the sea?

Marine iguanas have highly adaptive, unique characteristics fitting them for ocean feeding.

First, their tails are much flatter than other iguana species’ tails, helping them swim more efficiently in the waves. 

Second, their snouts are blunter than other iguana’s snouts, allowing them to better forage for algae and seaweed among the rocks. 

Third, marine iguana’s extra-long claws enable them to grip the rocky ocean floor so they can stay underwater longer during feeding.

They typically stay underwater for 15 to 30 minutes at a time. 

Fourth and finally, marine iguanas possess a special salt gland for expelling salt from their bodies.

When they feed in the ocean, marine iguanas ingest large amounts of saltwater.

While they need the water to keep themselves hydrated, the salt in it will dehydrate (and eventually kill them) if it’s not removed.

To remedy this problem, marine iguanas filter their blood in a special nasal gland.

The gland filters out the salt by “sneezing” it out, leaving only clean, salt-free water in their bodies. 

Marine Iguana Deep-Sea Diving

I know we just talked about marine iguanas swimming and foraging in the sea.

Still, we’re taking a deeper look (pun intended) into their ability to deep-sea dive because it truly deserves its own spotlight.

Now before you get the wrong idea, know only about 5% of marine iguanas dive deep into the ocean for food.

Most marine iguanas content themselves with the algae and seaweed found along the rocky, shallow waters of the shoreline.

So which iguanas deep-sea dive and why? 

Strong adult male iguanas are the only iguanas you’ll find diving deep into the sea.

These males, stronger and better suited to dive deep, avoid the competition for food along the shallow shores by foraging in deeper waters.

Strong male marine iguanas can dive down as far as 100 ft into the ocean and can forage for as long as an hour.

This is a remarkable feat for a land-dwelling reptile!

But remember, the marine iguana is still a cold-blooded reptile in need of heat to keep itself moving, and deep ocean waters are chilly!

This means the marine iguana must prepare for its deep-sea dive by basking in the sun to absorb extra heat.

If the marine iguana skips this basking step, the extreme temperature drop will render it immobile during its deep dive. 

Further, the male iguana will lower its heart rate and metabolism during a deep-sea dive to ensure its body temperature drops by 10° degrees Celsius, so its body retains adequate heat.

Marine Iguana’s Predators

Remarkably, the marine iguana has never had any natural predators.

Because of this, they are gentle and even docile creatures, making them quite popular with tourists.

However, even though no native predators have ever threatened the marine iguana’s existence, humans have introduced a multitude of invasive species, now threatening the lives of marine iguanas.

Today the Galapagos Islands are home to feral populations of dogs, cats, rats, and pigs, all of which threaten the lives of marine iguanas, especially the lives of their eggs and young. 

Marine Iguana’s Ability to Shrink

Another unique feature of the marine iguana is their ability to shrink.

During climate events like El Niño Southern Oscillation Event (or ENSO), the elevated rainfall and spike in water temperatures decrease the ocean’s algal growth, meaning there is much less food available for the marine iguana.

During these times of food shortage, the marine iguana will shrink in size by up to 20%. 

Why would they do this? It’s simple. Less body mass requires less food to keep oneself alive, so it is truly a survival mechanism.

And it’s not just their fat supply shrinking. It’s believed marine iguana’s very bones can shrink by up to 10% of their regular size!

When the food supply is back to normal, the marine iguana is quickly restored to its original size. 

What is Unique About the Marine Iguana

So to answer our original question, “what is unique about the marine iguana?” we’ve learned they possess multiple unique characteristics setting them apart from other reptiles and iguana species.

Marine iguanas are the only known marine reptile on earth, and the only reptile to live on a diet of seaweed and algae. 

Their highly adaptive bodies possess unique characteristics like a special salt gland to expel saltwater, flattened tails to help them swim, blunt noses and extra-long claws to aid them while foraging for food underwater, and the ability to shrink in size during times of food shortages.

Marine iguanas are truly remarkable lizards!