40 Fun Facts About Marine Iguana

How do marine iguanas get rid of the extra salt they swallow while feeding in the sea?

Sneezing it out clears the salt that glands at the nostrils filter from the blood. The spray often dries on the head as a crusty white wig.

What can adult marine iguanas do to their own bodies to survive years when food runs short?

Shrink in length is the trick, by as much as a fifth, and researchers suspect the bones themselves shorten. The iguanas grow back once the seaweed returns.

Which movie monster gives its name to a marine iguana subspecies from San Cristóbal Island?

Godzilla was a fitting choice: the designer of the 1998 Hollywood film modelled its monster on iguanas instead of the upright Japanese original.

Which naturalist threw a marine iguana into the sea again and again in 1835, only to see it swim back?

Charles Darwin found the lizard came straight back to the spot where he stood every time. He guessed that instinct told it the shore was safer than the sea.

Española's marine iguanas flush with bright colour when breeding, earning a nickname from which holiday?

Christmas iguanas flush red and green, and the name fits twice over: the colours are brightest in the breeding season, which begins in December.

Which BBC series made a viral sensation of marine iguana hatchlings fleeing from snakes in 2016?

Planet Earth II showed a group of racer snakes hunting the hatchlings in its Islands episode, and the clip spread across the internet that November.

What did a sailor find in 1835 on hauling up a marine iguana he had sunk with a weight for an hour?

It was quite active, an early clue to how long these lizards can hold their breath: a feeding dive may last more than half an hour.

Which body part does most of the work of driving a swimming marine iguana through the water?

Its tail is flattened from side to side and sweeps the animal along like a crocodile, while the legs mostly trail and the feet are barely webbed.

Which climate event kills off seaweed and can starve up to 90% of an island's marine iguanas?

El Niño cuts off the cold water that the seaweed needs, and the biggest iguanas suffer most because they need the most food.

When do most marine iguanas, which never dive, graze on the seaweed growing on the shoreline rocks?

At low tide the rocks lie bare, so the smaller iguanas dash down, snatch a few bites and run back to higher ground before the next wave arrives.

Which country governs the Galápagos and fully protects the marine iguana under its laws?

Ecuador keeps almost all of the iguana's range on shore inside a national park, and all of its range at sea inside a marine reserve.

In which ocean, cold here despite the equator, do all wild marine iguanas find their food?

Pacific water around the islands is only 11 to 23 °C at the surface, so every feeding trip chills the iguana and has to be kept short.

Which far bigger mammal shares the shore with marine iguanas, which sometimes crawl right over it?

Sea lions and iguanas mostly ignore each other, and neither animal seems to gain anything from living side by side.

Which introduced predator can kill fully grown marine iguanas, not only their eggs and young?

Feral dogs are hard to remove safely, because they also hold cat numbers down, and cats prey on the small iguanas.

How do rival marine iguanas usually settle a fight over a patch of breeding territory?

Butting heads is the rule: bony plates on the skull lock together and each lizard shoves, sometimes for hours, until the loser backs away.

Where does a marine iguana mother leave her eggs to hatch on their own a few months later?

In a sandy burrow up to 80 cm deep, which she digs herself in sand or volcanic ash; where good sites are scarce she guards it against other mothers.

Why do marine iguanas often spend the night pressed together in groups of up to fifty?

To conserve heat, the iguanas huddle because a reptile makes no warmth of its own and must hold on to what the day's sun gave it.

How do marine iguanas usually react when a person walks right up to them on the shore?

They stay put, having evolved with few land predators to fear; even iguanas that have been caught before are only slightly more wary the next time.

How are the marine iguana's ancestors thought to have reached the Galápagos from the mainland?

Drifting on debris such as logs is the leading idea, because the volcanic islands were never joined to any continent.

Why do marine iguanas at midday face the sun and lift their bodies high above the hot rock?

To cool off, the iguana points itself at the sun so that little of it is lit and lets air flow underneath; it pants as well.

Which bird is the main native predator of marine iguanas, able to take even weakened full-grown ones?

The Galápagos hawk is itself rare, with only a few hundred birds alive, so native hunters trouble the iguanas far less than introduced ones.

What happens to a marine iguana's heartbeat when it plunges into the cold sea to feed?

It slows sharply, to about 30 beats a minute against roughly 100 on sun-baked rock, so the blood circulates less and less warmth is lost.

Which gloomy nickname for marine iguanas was recorded in a famous diary of an 1835 visit?

Imps of darkness suited lizards as black as the lava they crawl over, and the dark colour helps them soak up sunshine quickly after a cold swim.

What do newly hatched marine iguanas feed on to pick up the gut bacteria that digest seaweed?

Their elders' droppings carry the microbes that break seaweed down, and a hatchling needs them before it can digest its own diet.

Which colour of seaweed can marine iguanas barely digest, starving when no other kind is left?

Brown seaweed can take over the rocks when the red and green kinds die back in hot years, and iguanas left with nothing else go hungry.

Which technology has helped researchers and online volunteers count marine iguanas on remote Galápagos shores?

Aerial drones photograph the colonies for the Iguanas from Above project, and citizen scientists help count the animals in what is meant to be the first full survey of the species.

What kind of disaster in 2001 cut Santa Fé Island's marine iguana population by almost two-thirds?

An oil spill from the ship Jessica did the damage even at low doses, probably by killing the gut bacteria that iguanas need to digest their food.

What matters most to a marine iguana choosing which territory holder she will mate with?

His sheer size counts most, with frequent head-bobbing and a well-placed plot also helping, while the area of the plot makes no difference.

How do small marine iguanas manage to mate unnoticed inside a bigger rival's guarded territory?

They resemble females in build and colour, so the owner overlooks them; they must be quick, because he chases them out as soon as he notices.

What does Amblyrhynchus, the Greek-derived genus name of the marine iguana, mean in English?

Blunt snout describes the flat face that lets the iguana press close to the rock and scrape off short seaweed with its sharp teeth.

Marine iguanas grow more watchful when they hear the alarm call of which other Galápagos animal?

The mockingbird is hunted by the same predator as the iguanas, so its warning tells them that a shared enemy is close.

What are lava lizards hunting when they scurry over marine iguanas basking on the shore?

Flies are drawn to the colonies, and the iguanas simply ignore the small lizards running over them.

What do the marine iguana's unusually dense, compact limb bones provide when it dives for food?

Ballast matters because the iguana naturally floats: if it stops swimming or lets go of the rock, it bobs back up to the surface.

Which wildlife trade treaty gave the marine iguana its highest level of protection in 2025?

CITES moved every Galápagos iguana species to its top tier, which prohibits all international commercial trade in the animals.

Which island is home to by far the largest population of marine iguanas, perhaps two-fifths of them all?

Fernandina's total is still hazy, with estimates running from 15,000 to 120,000, because iguanas on jagged lava shores are so hard to count.

What do biologists call a cluster of breeding territories that marine iguanas defend side by side?

A lek lets the other sex stroll between suitors and compare them, and those holding a plot near the middle tend to mate most.

On which tiny island have marine iguanas bred with their land-dwelling cousins to produce rare hybrids?

South Plaza is so narrow that the two species cannot avoid each other; the hybrids have marine fathers, live on land and seem to be sterile.

Thomas Bell named the marine iguana in 1825 but wrongly believed his specimen came from which country?

Mexico was a mistake, as the species lives only in the Galápagos, yet Bell still judged from its short head and strong claws that it lived strangely.

How does a marine iguana that has already mated turn away any further suitors who approach her?

Nodding at them is enough: she mates only once in a season, whereas a territory holder will mate with many partners if he gets the chance.

Which rule on certain coastal roads in the Galápagos is meant to protect young marine iguanas?

Lower speed limits cut the danger from cars in the small settled part of the islands; about 97% of the land is national park.