Sometimes, you can look at an animal and their name just makes sense. Tiger sharks have tiger-like stripes, sea slugs look like land slugs and blue whales are, well, quite blue. The same thing is true for the aptly named unicornfish.

As you can probably guess, the unicornfish gets its moniker from the unicorn-horn-like protrusion sticking out of its face. But what is that distinctive feature for? And what else is there to know about the unicornfish? Read on to have all your burning unicornfish questions satisfied.

What is a unicornfish?

Unicornfishes comprise a group of fish in the genus Naso, which is under the family Acanthuridae. You might know other fish in the family, including tangs and surgeonfishes (including the blue tang made famous by Dory in Finding Nemo). There are about 19 species within the genus Naso, but only some of them have the iconic “horn” protruding from their faces.

Where can you find unicornfish?

You can find unicornfishes in the tropical and subtropical regions in the Indo-Pacific seas (sorry Atlantic Coast residents, no unicornfish for you!) They typically find shelter in coral reef structures and can also be seen swimming over the top of the reef to feed. They are classified as diurnal planktivores, meaning they eat small plankton during the daylight hours. When they’re not feeding, they like to hide in nooks and crannies on the reef. Although it may look like they’re not up to much when they hide, unicornfish play an important role in the reef: Their waste helps provide nutrients to the corals. 

What’s the deal with the horn?

Only nine of the 19 species within Naso have the horn-like protuberances that give them their name. There are two types of “horns”—one that is actually shaped like a long horn and one that is more rounded.

Scientists aren’t entirely sure why unicornfishes have their horns, but there are some theories. One thought is that males use their horns as a way to signal to females that they are good mates. They also can change the color of their horns to “compete” against other males and stand out to females. Although both males and females have the protuberance, it appears that mostly males are the ones that change their horn color.

What’s the status of unicornfish?

Good news! According to the IUCN Red List, many species of unicornfish are considered of “least concern,” meaning we aren’t currently worried about them going extinct. But that doesn’t mean they’re out of the woods (or out of the seaweed, that is!): Like many species, unicornfishes rely on healthy, sustainable reef ecosystems. Coral reefs are currently under threat from climate change, and there is no healthy future for our reefs—and the animals who depend on them—unless we act now to reduce greenhouse gas pollution. Take action with Ocean Conservancy to urge policymakers to combat climate change before it’s too late.