22 Moray Eel Facts that Will Endear [or Terrify] You

Moray eel (Muraenidae)
Moray eel (Muraenidae).

With their big, double jaws; sharp, jagged teeth; and skin covered in a toxic slime, moray eels (Muraenidae) are among the most terrifying animals in the ocean. That is, until you get to know them. And once you do, you’ll likely come to appreciate them for their unique traits. I certainly do.

A Moray Eel Named Waldo

I have to give credit to my fondness for moray eels to one in particular. His name was Waldo and he lived in the Cayman Islands. I met him as a teenager on one of my first scuba diving trips. As a teen, I was fortunate to learn how to dive. My dad is a diving enthusiast, and he has a family rule that he’ll pay for any kid or grandkid who wants to get certified. I have my dad to thank for instilling in me a love for the ocean.

As a conservationist, I know the pitfalls of treating wild animals like pets. In general, I believe it’s ok for people to observe wild animals, but that we should otherwise leave them alone. I guess I can assuage my guilt about feeding Waldo with the fact that he was already very tame when I met him. Divers had been visiting and feeding him for years.

I have no idea when divers started feeding Waldo, but he was somewhat of a celebrity in the Cayman diving community.

On dive trips, we would visit him at his cave, and patiently wait for him to come out. He always did. And he was massive. I’m guessing 8 or 9 feet long. When feeding him chicken (one of his favorite treats), we’d have to take care so he wouldn’t mistakenly bite our fingers off. He would swim all around us, even though our legs, and then retreat back to his cave, only to pop his head out again.

You can say this article is very much a tribute to Waldo. He was an underwater ambassador who inspired me to learn more about his kind and to share that information with the world. Here are some interesting facts and frequently asked questions about these “aliens” of the deep – moray eels.

1. Are moray eels dangerous?

Finespotted moray eel
Finespotted moray (Gymnothorax dovii).

Because they look like monsters or the alien in Aliens, a common question many people ask is if moray eels are dangerous. While moray eels can be unpredictable and aggressive, they are rarely attack people. When they do, however, they can do some damage because, like a pit bull, they don’t like to let go. As humans, we have to accept the fact that any time we would engage with a wild moray eel would be on their turf, so an attack being unprovoked or not is a matter of interpretation.

Moray eels are, however, deadly to their prey, which I’ll explain more about below.

2. Can a moray eel kill you?

Technically, a moray eel could kill you. If the bite itself didn’t kill you, a secondary infection in the bite could be deadly. But examples of moray eels killing people by attacking them are virtually non-existent. If you know of any examples, write to me!

There are, however, no shortage of stories about famous kings, such as King Henry I of England and King Alexander III of Scotland, as well as everyday people eating eels and dying. Apparently, poisoning people with eels was not uncommon centuries ago in Anglo Saxon and Celtic culture. It seems that people ate a lot of fish, including eels.

3. Are moray eels slimy?

Yes, moray eels are slimy. Their skin secretes a thin, clear mucus, which forms a protective layer. This mucus helps them to swim and glide through the water without friction. It also make it easier for them to burrow in the sand, as the slime acts like a glue, causing the small sand granules to stick, thus creating create grip when the eel burrows. While their slime attracts and holds microorganisms, in a symbiotic relationship, cleaner shrimp eat the organisms off the moray eel’s skin.

4. Are moray eels poisonous?

Moray eels are poisonous in a few ways. While they are not venomous like snakes – meaning they spray poison when threatened or attacking prey, they do secrete poison. For one, the slime on their skin has several toxins in it. Among other things, these toxins will destroy red blood cells in the creature that touches the slime.

In contrast to other marine animals, as well as reptiles like poison dart frogs, which generate toxins by eating other creatures that are toxic, the yellow moray eel, in particular, is capable of creating these toxins themselves. (And scientists assume other moray species can do this too, however, not enough scientific research has been done yet on other species of morays.)

Extra-Painful Bites

Bites from moray eels are known to be far more painful than bites from animals with similarly-sized jaws. As with sharks, the direction that of the moray eel’s teeth make pulling away from their bites even more destructive. However, marine biologists believe the additional pain from a moray eel bit is due to the same toxins on their skin being emitted from their mouths.

Because moray eels are capable of storing high levels of toxins in their bodies, they are considered unsafe to eat.

5. Are moray eels fish or reptiles?

While they resemble snakes, moray eels are fish, not reptiles.

Here’s a video from Deep Marine Sciences that gives a quick overview of morays:

6. Are moray eels related to snakes?

Even though they look a lot like snakes, moray eels are not related to snakes, based on what we know about their evolution. In fact, many aspects of how moray eels evolved still baffle scientists, but they believe both their long bodies and second, pharyngeal jaw evolved due to their habitats, of living in caves and crevices.

7. Are moray eels friendly?

While Waldo was clearly a very friendly eel, generally moray eels are shy, preferring the reclusiveness of their caves. While they do come out to hunt, you don’t see them swimming around coral reefs as often as you’ll see parrot fish, angel fish, and others.

One of the reasons moray eels look so scary is that they open their mouths quite a bit. However, unlike a snarling lion, showing his teeth, the moray eel opens and closes his mouth to breathe. By routinely opening and closing their mouths, they push water (and therefore oxygen) through their relatively small gills.

8. Where do moray eels live?

White-eyed moray Eel (Gymnothorax thyrsoideus), Philippines. Photo: Maliy Sergii.

There are over 200 species of moray eels and they can be found mainly in tropical waters around the world, though some are found in colder, temperate waters. One-hundred-fifty of these species live in the Indo-Pacific Ocean. While they are primarily found in saltwater, some species live in brackish water and freshwater. Those who live in the ocean are generally found in depths shallower than 100 feet because this is where they find prey.

As was the case with Waldo, who lived in a cave, moray eels live in and near places where they can find shelter, including coral reefs, crevices, and rocky slopes. They are benthic animals, meaning they spend more of their time near the ocean floor vs. the surface as dolphins do.

9. What do moray eels look like?

As you can see in some of these photos, moray eels vary in color, such as brown, yellow, blue, and green, as well as patterns, from solid to striped to speckled. These different hues and patterns help them to be camouflaged in their environment. And all morays have a long dorsal find that runs down their bodies.

This video from David Whitehead shows some moray eels in action:

10. What size are moray eels?

Moray eels range in size as well. Two of the smallest are the Hawaiian dwarf (Gymnothorax melatremus), which is about 12 inches long (30.5 cm) and the minute moray (Anarchias galapagensis), which is only 6.7 inches (17 cm). And the largest ever discovered (Gymnothorax javanicus) was 11 feet long (3.4 meters) and weighed 150 pounds (68 kg).

11. How long do moray eels live?

In the wild, moray eels can live from around 10 – 40 years.

12. What do moray eels eat?

Moray eels prey primarily on smaller fish, including squid, octopus, damsel fish, cardinal fish, cuttlefish, and crustaceans.

13. How do they hunt?

Known as ambush predators, moray eels wait for their prey vs. going out and finding it as a shark does. But don’t let this seeming passivity fool you. Morays are quite deadly. They actually have two sets of jaws. One set is deep within their throat. The first set catches and holds the prey, then the second set is mobilized.

This outer jaws have sharp, piercing teeth that curve backwards towards the eel’s throat. This design prevents prey from escaping out of the eel’s mouth.

Then, once the is secured in the eel’s mouth, the second set of jaws is unleashed. It snatches the prey and delivers it to the eel’s esophagus to be swallowed.

Even though eels and snakes are not related on an evolutionary timeline, they do resemble each other in the way that they can eat large prey, despite having long, thin bodies. But while the snake’s jaw separates to expand, the eel utilizes its double-jawed system to crush and swallow its prey.

Diagram of moray eel pharyngeal jaws.
Moray eels have two sets of jaws. The first captures and holds their prey. The second, pharyngeal jaws, which inspired the monster in the movie Alien, advances into the mouth to move prey from the oral jaws to the esophagus for swallowing. Diagram: Zina Deretsky, National Science Foundation, Rita Mehta, UC Davis, and Ryan Wilson.

14. Are moray eels nocturnal?

Moray eels are primarily nocturnal. We would see them more often on night dives vs. during the day. However, Waldo had adapted to come out at all times of the day for free food.

15. Do they have predators?

For the most part, moray eels are apex predators. However, barracudas, groupers, and sea snakes will eat smaller moray eels.

16. How do moray eels reproduce?

Moray eel reproduction and life cycle
Moray eel reproduction and life cycle.

Moray eels don’t have a set season for mating. Their decision to reproduce is more dependent on food and habitat conditions. For instance, warm water increases the chances that they will mate. They are not known to be monogamous either. A female will lay her eggs in an area that seems safe from predators, then release an odor, which attracts the male. The male will then fertilize the eggs, which hatch in 5-6 weeks. The hatched eggs become a clear larvae, which can drift in the ocean for as long as two years.

17. Are moray eels blind?

When we fed Waldo, we would carefully tuck our fingers and thumb into a fist when holding the chicken so he wouldn’t bit our fingers off. It wasn’t because he was aggressive, it was because moray eels are known to have poor vision. Instead, they rely more on their sense of smell and sensory perception of currents in the water.

18. Are moray eels smart?

Undulated moray eel
An undulated moray eel (Gymnothorax undulatus).

While it’s hard to assess the intelligence some animals, scientists consider moray eels to be relatively intelligent compared to other fish. For one, they are known to hunt cooperatively with other fish, namely groupers. The grouper will chase its prey, and if the prey tries to hide inside a small cave or crevice, the grouper will alert (or stir up) a moray eel to chase the prey into the cave. Sometimes the prey comes out and the grouper catches it, at other times, it’s the moray’s win.

By the same token, Waldo, the eel, learned to be docile with scuba divers because we fed him. Whereas, moray eels who live in areas where they have little to no exposure to recreational divers can be more aggressive.

In addition, moray eels do not take well to captivity, and have been known to stop eating while in captivity.

19. Can you eat moray eels?

Moray eels can be toxic to eat because, as apex predators, they are high on the food chain and can accumulate large amounts of toxins from eating other fish.

Furthermore, as apex predators, morays are an important part of the ecosystems where they live, keeping fish populations in balance.

Marine ecosystems around the world are on the verge of collapsing due to the combined threat of over-fishing and climate change. Thus, moray eels should not be considered as a food source for human beings.

20. Where can you dive with moray eels?

Mediterranean moray eel
Mediterranean moray (Muraena helena), Croatia. Photo: Elapied.

Because they can be found in so many places, there are plenty of diving opportunities to see moray eels. While seeing them snorkeling can be far more difficult, sometimes snorkeling with dive boats will give you the chance. Here are some places to see moray eels in the wild. Visit Dive the World for more info.

Caribbean / Atlantic Ocean

  • The Bahamas
  • Belize
  • Cayman Islands
  • Honduras
  • Saba / St. Kitts
  • Turks and Caicos Islands

Oceania

  • Australia
  • Fiji
  • Palau
  • Solomon Islands

Pacific Ocean

  • Caño Island / Cocos Island
  • Galapagos Islands
  • Hawaii
  • Mexico

Red Sea / Middle East / Indian Ocean

  • Egypt
  • Maldives
  • Oman
  • Sudan

Southeast Asia

  • Indonesia
  • Malaysia
  • Myanmar
  • Philippines
  • Thailand

21. Are moray eels endangered?

The green moray eel (Gymnothorax funebris) is classified as a species of Least Concern on the IUCN Red List, and other species of morays are also considered to be doing well. The IUCN classifies species that are of Least Concern as not threatened because they are not facing imminent threats. (And only species that have been evaluated by scientists can be placed on this list.)

However, some conservationists argue that we should not wait for animals to become endangered before we start protecting them.

22. How can I help moray eels?

Zebra moray eel
Zebra moray eel (Gymnomuraena zebra). Photo: Bill Eichenlaub, NPS.

Moray eels depend on the vitality of their natural habitats. So, you can help protect them by supporting organizations that focus on marine and coral reef conservation. Here are some organizations that are doing that.

Organizations that Protect Moray Eels

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