What’s the difference between a seal and a sea lion?

Four-minute read

I brought this burning question up in A Dolphin Pod so it’s only logical to elaborate here. By now you’ve probably noticed I’m a complete pedant when it comes to animal classification.

Let’s do this in reverse and start with the similarities. Firstly, they’re all pinnipeds and rather confusingly they’re also all seals. Like how all dolphins are all whales.

The pinnipeds are a group of 33 marine carnivores that have spread out all over the world. They all have a similar body plan (largely seal-shaped), big sharp (or crazy-shaped) teeth and (sometimes clawed) flippers.

They also all have whiskers so sensitive they can detect changes in the water pressure around them. That means they can track down a fish without the benefit of having seen it first.

While we’re on whiskers I need you to know how cool they are. Whiskers have an important function and work in an absolutely remarkable way. They’re specialised hairs that basically act like our fingertips. Rat whiskers are sensitive enough to tell the difference between rough and smooth sandpaper.

The hairs are arranged symmetrically on the face and each is connected to a nerve that goes straight to the brain. The position of each whisker on the face is mirrored in the brain. Information goes from the tip of the whisker to the corresponding region of the brain, so the animal can build up a 3D picture of the immediate environment.

That means the animal can sense changes in the air - or water - in front of them. If you didn’t understand that rambling explanation then check out this video. Watch it even if you already get it, it’s a six-minute rollercoaster ride that is not to be missed. Y’all know I know how to party.

Back to pinnipeds. There are three families. Walruses are all on their own, then the rest are divided into eared seals and true seals.

Sea lions are eared seals. As the name suggests, they have external ear flaps. True seals don’t. Just like dolphins they still have little openings where their ancestors’ ears once were but have excellent hearing even without external hardware.

Sea lions are also much for manoeuvrable on land. Their front flippers have evolved to be longer and more versatile than a seal’s because sea lions spend more time on land than their earless cousins. Sea lions can pretty much walk on four legs but seals have no choice but to hop around on their bellies like a horizontal space hopper.

That’s why you’re more likely to see sea lions performing in a show. I’m not saying there are no seal shows, I know for a fact there are plenty. I’ve been in seal shows. But sea lions are the more traditional choice because their agility makes them better entertainers.

There’s also a difference in the kind of sounds they make. A lot of you would recognise the bark of a sea lion. It’s a commonly used sound effect in TV and movies. But seals sound a bit different.

Seals make a lot of weird noises. They emit deep, guttural growls, high-pitched whistles and staccato chirps. Sea lions make other noises too, the point I’m making is that you probably won’t have heard a true seal before.

The final difference I’ll highlight is their social behaviour. If you’ve seen sea lions in the wild you might have noticed they like the spend their time in big groups. Sometimes they congregate in the thousands. Whether they’re lying out on the rocks in the sun or zipping through the waves they generally stick together.

Seals, on the other hand, prefer to live solitary lives. The only time you’ll see a whole bunch of seals together is breeding season. That’s the only time they need to meet up. They’re compelled to do it so that the species doesn’t die out. They’re happy to do their own thing the rest of the year.

And that’s about it for now on the differences between seals and sea lions. There are probably more and if any occur to me, rest assured I’ll be updating you as fast as possible.