Why Do Other Animals Sit on Capybaras?

In the wild, the animals that sit on capybaras are almost always birds, and they're there to eat: they pick off ticks, snap up the flies that land on the capybara, and catch the insects it stirs up as it walks through the grass. The capybara lets them because they take bugs away and a small bird is no threat. The viral photos of monkeys, cats and ducks sitting on capybaras are something else: nearly all come from zoos and parks, and nobody has actually studied why it happens. Here's what is known, with sources.

The birds that clean them

In Brazil, several bird species forage on capybaras. Researchers Ivan and Cristina Sazima gathered the known cases of "cleaner birds" in the country: jacanas, cowbirds and other birds that pick off ticks, comb through the fur and catch the horseflies that land on capybaras (Sazima and Sazima, Biota Neotropica, 2010).

The most interesting detail: some capybaras held still, "posing," while a bird worked on them. They don't just tolerate the birds; they seem to know it's a good deal.

The birds that hunt from their backs

There's a second kind of passenger. The cattle tyrant, a small flycatcher, doesn't always go for ticks: it uses the capybara as a perch and a beater. As the capybara walks and grazes, it flushes insects out of the grass, and the bird catches them.

A study in Campinas, Brazil, timed it: cattle tyrants feeding alongside capybaras stayed in one spot for about 11 minutes on average, while those feeding alone stayed under 4 (Andrade and Brumatti, Lundiana, 2013). The authors think hunting is simply better next to a capybara, so the birds have no reason to leave.

What the capybara gets

It depends on the bird:

• With birds that remove ticks and flies, the capybara gets cleaned. Both sides win.
• With birds that only hunt insects beside it, the capybara doesn't gain much, but doesn't lose anything either. Biologists call that commensalism: one benefits and the other isn't affected.

And it isn't always peaceful. In the same Sazima work, a large capybara stood up and walked off after a caracara, a bird of prey, yanked a tick from it. We told that story in why capybaras are so calm.

And the monkeys, cats and ducks in the photos?

Those are the photos that go viral: a monkey sitting on a capybara, a cat curled up on top, a row of ducklings on its back. Nearly all of them come from zoos, parks or places where different animals live together and know each other.

The honest truth is that no study explains why it happens. Here's what can fairly be said:

• A capybara is big, broad and warm, with a flat back. It's a good place to sit.
• It hardly reacts. An animal that doesn't startle is a good place to rest.
• In captivity, animals get used to each other, and what would be rare in the wild becomes normal.

Beyond that, any explanation ("all animals love them," "they're the best friends of the animal kingdom") is a nice story, but it isn't proven.

If there's a capybara near you

Don't put your cat on one for a photo. A calm capybara is still a wild animal, and if you see one at a zoo, follow the zoo's rules. If you want to see them at their most relaxed, watch them soak in Japan: the capybara hot spring bath.

Capy and Bara

Capy, our capybara, carries everybody too: Pincho on her head and Bara on her back. But she's a character, not a real animal, and she loves it. Meet them here.