They both live in the water! They both have long pointy things on the fronts of their faces! They look like they would love to fight a fishy duel! Still, while it’s easy to see how we could confuse the two, it turns out that narwhals and swordfish are actually totally different.
What is their “spike” made of, anyway?
While the narwhal looks like some kind of magical sea unicorn, it turns out that its “horn” is not a horn at all — it’s a tusk! The big, twisted spike you see coming out of the front of a narwhal is really one of its teeth: a canine. This is a very unusual adaptation, to have exactly one tooth longer than the others; we’re used to seeing animals that are more “symmetric”, or the same on the left side and the right side. Still, asymmetric adaptation does happen (just look at the very photogenic fiddler crab.) Zoologists used to think the narwhal’s tusk is used to fight other narwhals, but now we think narwhals may talk to each other by touching tusks, and they can “tap” fish with them to stun them. A narwhal’s tusk grows between 1.5 and 3 meters and will weigh about 10 kilograms.
Meanwhile, the swordfish’s “sword” is a long bill — basically, it’s their upper lip! The sword bone grows forward out of the swordfish’s skull and is not only very strong, it’s able to repair itself after breaking. Zoologists say the swordfish will not stab with its sword, as you might assume; instead, they slash with it, like a knife. Swordfish are predators, and are known for hunting lots of smaller fish; they’re also famous for their very high swimming speed. A large swordfish’s entire body can be almost 3 meters long — the same size as a large narwhal’s tusk — so you can see they have a size disadvantage.
Fish vs Mammals
- A swordfish has gills and breathes water. If it were in the air or on land, it couldn’t breathe!
- A swordfish lays eggs.
- A swordfish has scales (when it’s younger).
- A swordfish has cold blood. This means their body temperature is the same as their environment.*
Together, these things make it very clear: a swordfish is definitely a true fish!
*However, swordfish are unusual among fish in that their special blood vessels keep the brain and eyes warmer.
- A narwhal has lungs, and breathes air. They need to come to the surface to breathe!
- A narwhal gives birth to live young, and feeds them with milk.
- A narwhal has hair, though they lose their hair just after they’re born.
- A narwhal has warm blood.
So, it’s clear that a narwhal — just like you and me — is a mammal, not a fish!
Where do they live?
Swordfish live mostly in warmer waters and can dive to around 550 meters below the surface. Narwhals, on the other hand, only live at the very top of the world, in the Arctic Ocean. Also, Narwhals can dive three times deeper than a swordfish, down to 1500 meters below the surface — even though they have to hold their breath.
As you can see, swordfish and narwhals have a lot of major differences, even if they seem similar.