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13 Interesting Facts About Marine Iguanas in the Galapagos

Looking to enjoy some interesting facts about marine iguanas? I’ve got you covered with these 13 impressive marine iguana facts.

interesting facts about marine iguanas

Sea Iguanas?

I love reptiles. Yes, some of the larger species can be scary, but still awesome! Marine iguanas are super cool. Like most lizard-like reptiles, they have an amusing gait. They lift themselves up and look like a one-man marching band.

Marine iguanas, like the name implies, spend a lot of time in the ocean, swimming and eating.

Marine Iguanas by the Numbers

  • Marine iguanas, like most animals, have an unpronounceable latin nameAmblyrhynchus cristatus 
  • Length: 4-5 feet (1.2-1.5 m)
  • Weight: 1-3.3 lbs (.5-1.5 kg).
  • Color: “black; black like the night” (Batman). Or a light shade of gray. Read on to learn why they sometimes look like a pack of waxy crayons.
  • Cool feature: marine iguanas have spikes running all down their back and tail.

They are endemic to the Galapagos Islands, which means that’s where they originally came from.

You can always find them on the black lava all around the islands, but the closer you are to the water, the better your chances.

galapagos marine iguana facts

13 Interesting Facts About Marine Iguanas

1. Why are marine iguanas black?

Dark colors absorb sunlight. Since marine iguanas are cold blooded, their black skin helps them to absorb lots of heat from the sun so they can dive into the cold ocean.

After each dive, they have to return to their sun-basking because body heat can drop up to 50°F (10°C).

They are extremely vulnerable to predators while they sunbathe because they are too cold to move quickly.

marine iguana sunbathing

2. Why do marine iguanas sneeze?

Because they eat in salt water, they have to get the salt out somehow so it doesn’t hurt their insides. What better way then to sneeze and snort all over the place? It looks awesome and it’s effective. Win-win!

The salt ends up hitting the top of their head and back, accounting for that white color. They’re encrusted in their own salt boogers!!

marine iguana interesting facts

3. Can marine iguanas breathe underwater?

No. Marine iguanas cannot breathe underwater because the don’t have gills like a fish. However, they can hold their breath for an impressive amount of time.

4. How long can marine iguanas hold their breath?

They generally dive for 30-40 minutes but can hold their breath for even longer, as proved by old Charlie:

In “The Voyage of the Beagle,” Charles Darwin wrote, “A seaman on board sank one [a marine iguana], with a heavy weight attached to it, thinking thus to kill it directly; but when, an hour afterward, he drew up the line, it was quite active.”

sea iguana facts

5. Why do marine iguanas nod?

Male marine iguanas will fight for their territories by, well, fighting. They will stare off while dramatically nodding their heads in a most comical fashion, and then they will brawl all over each other and fight like a couple of men! Oh, wait… they are a couple of men.

When we visited the Galapagos, I nodded at them, and I guess they figured a little blonde girl in khaki shorts was quite a threat.

They nodded back and started freaking out at me. I freaked. They freaked. End of story.

6. What do marine iguanas eat?

They feed mainly on seaweed and algae. Younger marine iguanas will feed on algae at low tide because they do not yet have the strength to dive in the cold water.

The adults will dive up to 9 feet (2.7 m) deep to graze on the seaweed that’s anchored to the rocks.

Because the marine iguanas have very sharp claws and teeth, people understandably assume that they are carnivorous.

They use these super sharp teeth and claws to scrape algae and seaweed and to hold on to the rocks.

sea iguana

7. Why do some marine iguanas look like walking rainbows?

During mating season, male marine iguanas show off very bright colors to attract mates. These colors can range from blues and greens, to reds and pinks. It is an amazing thing to see!

8. Why are marine iguanas all different sizes?

If the island where they live has a plentiful underwater supply of algae, they will grow much bigger than if they didn’t have that amount of food.

Their size can affect breeding; the males gravitate more toward larger females because they lay the biggest eggs.

marine iguana fun facts

The sub-species also affects size, gives us a helpful list of subspecies of the Galapagos marine iguana:

  • Amblyrhynchus cristatus albemarlensis
  • Amblyrhynchus cristatus cristatus
  • Amblyrhynchus cristatus hassi
  • Amblyrhynchus cristatus mertensi
  • Amblyrhynchus cristatus nanus
  • Amblyrhynchus cristatus sielmanni
  • Amblyrhynchus cristatus venustissimus

Yeah, so lots of latin, yeah! (if you like that sort of thing). Anyway, they all come from the same origin, Amblyrhynchus cristatus. Blabidy babidy blah…

9. What are the main predators of marine iguanas?

In short, humans. Dogs and cats pose a threat to the Galapagos marine iguanas because the original settlers on the islands brought their pets with them.

Feral dogs and cats will attack the iguanas and their nests.

The Galapagos hawk and the great blue heron are the natural predators of the marine iguanas, something that humans had nothing to do with. Galapagos hawks will hunt the full grown iguanas, whereas the herons will eat the small hatchlings.

10. How do marine iguanas swim?

It’s very interesting to watch an iguana swim. They tuck their front legs under their bellies and point their back legs straight back.

They use their tail as the primary way of maneuvering through the water, by twisting their whole bodies back and forth in line with their tails.

From the back of their heads all the way down to the end of their tail the back is raised slightly, thus creating a dorsal fin.

marine iguana facts

11. How many eggs do marine iguanas lay?

The bigger they are, the harder they lay…. okay, that’s cheesy; whatever. The smaller marine iguanas may only lay one egg, while the larger ones will lay up to six.

12. Symbiosis?! Eeeeeekkk!!!

Is this Spiderman and Venom?? Not quite that close of a symbiotic relationship, but the marine iguanas depend on mockingbirds.

Why? When a Galapagos hawk is in the area, the mockingbird lets out a distinctive call. The marine iguanas recognize this and run for cover.

13. Are Galápagos marine iguanas the only marine iguanas?

Yes. Galapagos marine iguanas are the only iguanas that feed and swim in the ocean!

galapagos iguana facts

One Ugly Mermaid

Well, those are my 13 interesting facts about marine iguanas. Which is your favorite? Did I miss one? Please tell me in the comments!

Check out another amazing Galapagos animal.

Alison M Charles

Sunday 13th of June 2021

Amazing facts I didn't know quite a lot of them. I am trying to arrange a trip to the Galapagos but it will probably be in 2 years time when the world get back to normal. Thank you very much for sharing these I cannot wait to see the iguana, tortoises and the blue boobies which I have tattooed on me already .

Noy McCollum

Monday 31st of August 2020

That was a great article. I was educated and entertained-good job considering no one has an attention span to read past a paragraph.

Vic Ellisor

Saturday 25th of January 2020

Noticed these iguanas have five fingers with claws. Is one of the used as a "thumb"?

How to Use a Selfie Stick for Better Animal Photos (Galapagos Animal Selfies) | Click Like This

Monday 25th of February 2019

[…] a marine iguana on Floreana […]

raymond tolentino santana

Monday 3rd of December 2018

thanks for the marine iguanas it helped on my research.

Drew Haines

Monday 3rd of December 2018

I'm so glad you enjoyed it, thanks for commenting! What are you researching for? Anything else you would like to know that I might be able to help with?