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Listen: Hippo back talk could help save one of the world's last huge herbivores

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Hippopotamuses are very vocal animals, although we know little about why they make so much noise.

They often call and respond to each other, like a conversation.

According to new research, hippos can even recognize their pals’ voices when they’re recorded and played by a loudspeaker.

Nicolas Mathevon

In a paper published this week in the journal Current Biology, researchers tracked hippos’ reactions when they listened to calls from familiar and unfamiliar peers.

Nicolas Mathevon

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They studied seven groups of hippos living in Mozambique’s Maputo Special Reserve.

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For five of the seven groups studied, the researchers played back calls from three types of individuals:

- Hippos from the same group

- Neighbor hippos living in the same lake

- Complete strangers

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They focused on one type of call dubbed the “wheeze honk” — a low rumble that travels over long distances. This call is thought to play an important role in hippo social bonding.

When the researchers played a recorded wheeze honk over a speaker, the hippos talked back.

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Here’s one group responding to a call:

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The hippos pause for a few seconds after listening, then respond back.

Nicolas Mathevon

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When the voices of unfamiliar hippos played over the speaker, the animals listening would respond with more aggression than they did with the calls of group members or neighbors.

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Knowing this, researchers say, could potentially help with hippo conservation efforts.

Hippos are recognized as a threatened species, and their numbers have dramatically decreased in recent years.

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Relocating hippos can be a challenge because they are incredibly territorial.

But finding a way to make hippos more comfortable with strangers could start with exposing them to the outsider’s voice.

“One precaution might be to broadcast their voices from a loudspeaker to the groups already present so that they become accustomed to them and their aggression gradually decreases.”

Study co-author Nicolas Mathevon, in a statement.

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