The Marine Iguana Is The World's Only Seafaring Lizard

Marine iguanas also have wide-set eyes, blunt snouts, sharp teeth and flattened tails. Charles Darwin famously described the Galapagos marine iguanas as "hideous-looking" and the "most disgusting, clumsy lizards."

While their features may make them awkward-looking on land, their sharp teeth are ideal for scraping algae off rocks underwater, and their flattened tails make them excellent swimmers, as they can propel themselves through the water.

They are primarily black or grey, though males can have colorations of red, yellow and green. Their dark coloration helps them absorb heat from the sun, an essential adaptation for regulating body temperature after foraging in cold ocean waters.

Adult male marine iguanas can reach lengths of around 4 feet (1.2 meters), while female marine iguanas are smaller, typically about 2 feet (0.6 meters) long.

The marine iguana diverged into about eight subspecies, each niche iguana population found on different islands in the Galápagos.

These subspecies vary in size and coloration depending on their habitat. For example, the Christmas iguanas of Española Island are known for their bright red and green hues during the breeding season, making them a favorite among visitors.

Marine iguanas are relatively gregarious, often gathering in large groups to bask together on volcanic rocks. This helps these cold-blooded reptiles warm up after diving in the ocean.

While they are peaceful, marine iguana colonies are constantly on the lookout for predators, including birds, snakes, crabs and sharks. The Galapagos hawk is their main predator.

Also, male marine iguanas are highly territorial during the breeding season, engaging in head-bobbing displays and occasional physical clashes to defend their space.

The life cycle of a marine iguana begins when females dig shallow nests in sandy or volcanic soil to lay their eggs. After about three months, the hatchlings emerge and must fend for themselves.

As they grow, juvenile marine iguanas transition from a terrestrial lifestyle to a marine one. Male marine iguanas reach sexual maturity around age 7, while females mature slightly earlier, around age 4. They typically live to about 12 years in the wild, with some reportedly surviving up to 60 years.

The primary diet of a Galápagos marine iguana consists of marine algae and seaweed. They graze on algae underwater and can hold their breath for up to 30 minutes while they feed. Their ability to dive as deep as 30 feet (9 meters) allows them to reach algae growing on deeper submerged rocks.

During rough seas, when underwater foraging becomes dangerous, marine iguanas switch to eating algae washed ashore. Their adaptability ensures they can survive even under less than ideal conditions.

Marine iguanas inhabit the rocky shores of the Galápagos Islands. The volcanic landscapes of the islands offer both foraging grounds for food and basking spots for warmth. The cold currents surrounding the Galápagos Islands provide nutrient-rich waters that support abundant algae growth.

Yes, the International Union for the Conservation of Nature (IUCN) lists marine iguanas as vulnerable to extinction. Marine iguana populations face several threats, including habitat destruction, climate change and feral predators (including hawks and feral animals like cats, dogs and rats) that feed on the young.

Their reliance on the marine environment also makes them vulnerable to changes in ocean temperatures caused by events like El Niño, which can drastically reduce algae availability and cause mass starvation.

Additionally, human activity — such as tourism and pollution — negatively impacts their fragile ecosystem.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.