10 Facts You’ll Find Fascinating About The Intriguing Marine Iguana

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Quick Facts

Scientific Name:  Amblyrhynchus cristatus

Common Names: Marine iguana, Sea iguana, Saltwater iguana, Galápagos marine iguana

Geographic Range: Galápagos Islands (Ecuador)

Life Span: 60 Years

 Conservation Status: Vulnerable

Top 10 List – Marine Iguana Facts

1. Marine Iguanas Have 11 Different Subspecies

As mentioned above, marine iguanas have 11 different subspecies. Originally only 7 subspecies were recognized. However, in 2017 another look was taken and 5 more subspecies were officially added to the list. Each subspecies occupies a different area of the Galapagos islands, and have slightly different coloration and sizes from each other. Amblyrhynchus cristatus venustissimus is one of the more unique subspecies due to its bright coloration.

2. Unsurprisingly, Marine Iguanas Need To Live Near Water To Survive

Marine iguanas are only found on the Galapagos Islands, in Ecuador. Thankfully these islands have warm tropical weather and access to both water and sandy areas. These are all essential for the marine iguana to survive and breed. While they do spend a large amount of time on land basking on steep rocky cliffs, low rock ledges, and intertidal flats, they don’t ever travel too far away from the water. They have also been spotted in marshes, mangroves, and of course sandy beaches where females lay their eggs.

3. These Large Lizards Are Actually Herbivores

One of the main reasons that marine iguanas don’t venture too far from shore is because the ocean is home to their main food source- algae and seaweed. Large males will swim out and dive to find their food. However, smaller males and females tend to stay in more shallow water to scavenge for algae. In deeper water, they use their large claws to hold themselves against the bottom of the ocean floor. They then use their short blunt snouts and razor-sharp teeth to scrape the algae off the rocks to eat. As an interesting fact, when marine iguanas have a lack of food available they not only get thinner, they will also shrink in length! When food becomes more abundant they will regrow to their original size again.

4. They Were Described By Charles Darwin as a “Hideously Looking Creature”

When Charles Darwin went to the Galapagos islands, he described the marine iguana as a “hideous looking creature, of a dirty black color, stupid, and sluggish.” We aren’t sure why Charles had such hate for the marine iguana, but we find them unique looking and an interesting part of wildlife on the Galapagos islands. Coloration, size, and appearance can all vary between the different subspecies. However, in general, marine iguanas have a thickset body and fairly short robust limbs. Adults have a row of spines extending from the nape of their neck to their tails, with the spines being larger on males. A laterally flattened tail similar to those of crocodiles help them swim and glide quickly through the water.

While exact coloration depends on the subspecies, females tend to be dark grey/black in color, and males become more colorful during the breeding season to attract females. Their weight can range from 2.2 – 26+ pounds, and their length ranges from 2 – 5 feet, which really shows the variety that marine iguanas come in in the wild.

5. Sometimes They Create Babies With Land Iguanas, Creating A New Hybrid Iguana

One of the facts that we find most interesting is that, unlike most animals who only stick within their specific species, marine iguanas have been known to occasionally breed with Galapagos land iguanas. This produces offspring that are considered a “hybrid” iguana and has characteristics of both marine and land iguanas. Oddly enough, these babies only seem to occur between male marine iguanas and female land iguanas. The babies are believed to be sterile, which is why they are so rare, as they cannot reproduce to keep the new population of hybrids going. These strange hybrids were first noted in 1981, however, they weren’t confirmed as true hybrids until 1997. These hybrids only seem to occur on the small island of Plaza Sur, which is only one-tenth of a mile in size. The hybrids have a distinct coloration that consists of dark grey and yellow.

6. They Are Considered A Vulnerable Species That Needs To Be Protected

Marine iguanas are considered vulnerable and are completely protected by national legislation in Ecuador. While the IUCN lists the marine iguana as a whole as vulnerable, the populations on San Cristobal, Santiago, and Genovesa Islands are considered endangered.

A few different things contribute to the threat of marine iguanas and their vulnerable state. The first is pollution such as oil spills which can be harmful to their health. Climate change as well is affecting temperatures which can further harm, the marine iguana population. Periodic El Nino events reduce the cold water, which lessens the algae essential for the marine iguana’s survival, and therefore drastically decreases their population. Finally, species that have been introduced to the island by people, such as cats, rats, dogs, and pigs can kill young marine iguanas, as well as eat the marine iguana’s eggs, which, of course, has a negative effect on their population as they are not naturally equipped to deal with these new predators.

7. Sometimes They Are Mistaken For Galapagose Land Iguanas

Sometimes marine iguanas can be mistaken for land iguanas due to them having a somewhat similar appearance and both being found on the Galapagos Islands. It is thought that marine and land iguanas descended from a common ancestor and that some millions of years ago they split and evolved into the two separate species they are today. This would explain why they do have quite a few similarities to each other.

8. Male Marine Iguanas Will Have Babies With Multiple Females

During the mating season, which is typically from December to March, male marine iguanas will compete with other males for the chance to reproduce as many female marine iguanas as possible. After that, the females will lay 1 – 6 eggs into a sandy nest on the beaches they inhabit. In areas where there are less suitable areas for nests, the female iguana will defend the nest for a couple of days to prevent it from being dug up by another female, before leaving the eggs on their own to incubate for 89 – 120 days. Once they hatch the hatchlings are on their own and must fend for themselves. Male iguanas are considered mature enough for breeding by 6 – 8 years, while females are considered mature at 3 – 5 years old.

9. Marine Iguanas Can Dive 65 Feet Underwater

Marine iguanas have many quirky habits, behaviors, and skills. They are the only lizard that spends a decent amount of time in the sea to feed and swim. They can hold their breaths for 10 plus minutes, as well as large males are able to dive more than 65 feet underwater when in search of food. When not feeding during the day, they bask in large colonies on rocks, regulating their temperature and warming up in the sun. One way they get all the excess saltwater out on their systems is by sneezing it out, which often leaves their face crusted in white salt., which can look a little silly.

10. Marine Iguanas Have a Good Relationship with Galapagos Mockingbirds

Surprisingly, marine iguanas have a unique reason why they get along so well with the Galapagos mockingbird. Galapagos Mockingbirds will cry out to alert other mockingbirds of hawks, which are a predator of not only the mockingbird but the marine iguana as well. Some iguanas, especially smaller or younger marine iguanas, have learned that this bird cry means danger and will run and hide to avoid being preyed upon by the hawk.

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