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Hippos are very vocal animals, exchanging signals like the “wheeze honk”. But not much is known about what these sounds mean. Two researchers found themselves thinking about this in Mozambique – where they were initially studying crocodiles.

Hippos are quite territorial and aggressive – and fast-moving. So the researchers kept a fair distance away as they conducted their experiment. They recorded hippo noises and played them back to the animals, watching to see how the hippos behaved. If the call came from an unknown hippo in a different social group, the response appeared to be aggressive. If the call was one they recognised, they were less inclined to be aggressive.

One way hippos show aggression is to spray dung.

The meaning of hippo sounds is useful to know for conservation efforts. Hippos and humans sometimes come into conflict and need to be moved for their own survival. Before relocating them, conservation managers could play them the sounds of the hippos they will be meeting in their new location, to familiarise them.

In this episode of Pasha, Nicolas Mathevon, professor in animal behaviour and bioacoustics at the University of Saint-Etienne, and Paulo Fonseca, professor in acoustic communication at the University of Lisbon, take us through their experiences of listening to hippos in Mozambique.

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Photo
“Specie Hippopotamus amphibius family of Hippopotamidae.” by PACO COMO, found on Shutterstock

Music
“Happy African Village” by John Bartmann, found on FreeMusicArchive.org licensed under CC0 1.

“African Moon” by John Bartmann, found on FreeMusicArchive.org licensed under CC0 1.

The researchers would like to thank the Maputo special reserve for allowing them to do the research on the property.