10 Incredible Facts About Marine Iguanas

Have you ever seen an iguana sneeze? Chances are you haven’t, unless you’ve visited the Galápagos Islands. There you can find a species of iguana that sneezes, shrinks, swims and performs other remarkable feats for survival. Stay tuned for a list of 10 incredible facts about marine iguanas!

1. Marine iguanas can shrink

Not many animals can expand and contract their bodies as needed. Marine iguanas, however, possess exactly this ability! In times of food scarcity, their bodies get even smaller, so they need less food. This is not just a matter of losing fat or muscle. The bones themselves shrink and the skeleton becomes more compact, making these large iguanas smaller.

Nor is it a negligible difference. Marine iguanas can lose up to 20% of their body weight. Then, when the food supply becomes more robust, they grow back to their former size. This can be repeated over the course of their lives if necessary.

2. Marine iguanas sneeze salt

Yes, you read that right! Marine iguanas actually expel salt through their noses. Because they spend time swimming in the salty sea, they ingest a large amount of salt. Unfortunately, this poses a health risk, as salt water in the body can cause dehydration. So they have to somehow get rid of the excess salt.

They do this by “sneezing” it out. Special glands in their nostrils filter out the salt and allow them to expel it. Visitors to the Galápagos Islands can often see marine iguanas performing this curious procedure. Not only that, but the iguanas are usually covered in a white crust from all the sneezing.

3. Marine iguanas graze underwater

Despite their ferocious appearance, marine iguanas are actually herbivores, just like many other iguana species. They prefer to feed on plant material between the rocks and pools, usually algae and seaweed. Underwater, they use their sharp claws to anchor themselves in place so they don’t float away.

Land lizards usually have long, pointed snouts. Marine iguanas, on the other hand, have evolved short, stubby noses to help them search for plants.

4. Marine iguanas are the only lizards in the world that like to swim

Not only are marine iguanas the only iguanas to regularly take to the water, but they are also the only marine lizard of any species. Scientists theorize that the marine iguanas were first brought to the Galápagos Islands as early as 5.7 million years ago. At this stage, it probably wasn’t able to swim at all. However, food shortages on land soon forced it to learn to forage underwater.

Now marine iguanas are master swimmers! They move like a snake underwater and can anchor themselves with their claws. They are still mainly terrestrial meaning they spend most of their time on land but they will never be afraid to dive in again.

5. The dark color of marine iguanas helps them swim

Almost everything in nature has a purpose, and the black or dark gray skin of marine iguanas is no exception. As reptiles, they are cold-blooded and rely on the sun to help regulate their internal temperature. They spend a lot of time on the black rocks in the sun, absorbing as much heat as possible before diving into the cold water.

Blacks are particularly good at absorbing the sun’s rays, speeding up this process. Without this feature, marine iguanas would struggle to stay underwater for more than a few minutes at a time. This would compromise their ability to eat, perhaps fatally.

6. Marine iguanas can drastically slow their heart rate

Amazingly, marine iguanas have another water-related adaptation. While submerged, they are able to lower their heart rate to half of what they would be on land. They can keep this up as long as they have to swim. It helps them to stay underwater for longer periods of time.

However, this adjustment has another advantage. Galápagos sharks are among the main predators of marine iguanas. These creatures are so finely tuned to underwater movement that even the vibration of a beating heart could distract them. By lowering their heart rates, marine iguanas can often slip under the radar and live another day for a swim.

7. Marine iguanas can use the call of a mockingbird as a signal to take cover

A recent study found a fascinating link between marine iguanas and Galápagos mockingbirds (Yes, there are mockingbirds in the Galápagos Islands!). Marine iguanas are non-vocal, meaning they rely on visual and olfactory communication. Mockingbirds, however, use different sounds to communicate danger to each other, such as that of birds of prey.

The scientists conducting the study didn’t think the iguanas could learn to correctly interpret the mockingbirds’ alarm call. However, they were proved wrong when the marine iguanas were not only vigilant in response to the calls, but also learned to escape danger!

8. Marine iguanas can hold their breath for up to 30-40 minutes

Marine iguanas do not have gills and therefore cannot breathe underwater. However, they can hold their breath for 30-40 minutes at a time, and some think they can hold it for longer. Charles Darwin, the famous naturalist, told a story of his travels about a sailor who tried to drown a marine iguana by lowering it over the side of the ship. After tying it to a rope, he left it there for an hour and then pulled it back up. To his horror, the iguana was still very much alive!

The ability to hold their breath for so long allows marine iguanas to graze underwater for extended periods of time before coming to the surface for air. Otherwise they would be very inefficient eaters.

9. Marine iguanas nod their heads to warn intruders

If you’ve ever been around marine iguanas, you may have noticed that they nod their heads. This peculiar behavior is not intended as friendly consent; rather, these lizards bow their heads as a warning to intruders or potential male rivals. It can serve as a harbinger of more serious action, so if you notice this behavior, pay attention and back off.

10. Marine iguanas change color during mating season

Male marine iguanas have a serious responsibility during the mating season: finding a mate! This means that they have to attract females in heat. The main way they do this is by changing the color of their bodies. While they are usually simply black or gray, males can add red or green to the mix during this time. As with many other species in the animal kingdom, the females are dark and dull all year round.

Unfortunately, environmentalists list marine iguanas as vulnerable to extinction. This is partly due to the limited area in which they live, but climate change and pollution are also responsible. Unfortunately, visitors to the island – both humans and animals – can play a role in disrupting the life cycles of marine iguanas. If this remarkable species is to continue, it is imperative that they continue to mate successfully and without visitor intervention.