Hippopotamuses Spray Poop When They Recognize Sounds Both of Friends and Rivals

To test if the wheeze honk Hippopotamus amphibious or hippopotamuses are making is used to recognized friends and strangers, researchers recently recorded the changing honks of seven different hippopotamus groups living in the lake-field Maputo Special Reserve of Mozambique and played them back to each of the groups from a loudspeaker.

As indicated in a Science report, the said animal is not known for keeping its mouth closed. The gigantic semiaquatic mammals, as earlier mentioned, are making a "wheeze honk" with members of their social group that can be heard farther than one kilometer.

Such calls fell into one of three classifications which include first, from a hippo in the same clan, second from a hippopotamus that lives in the same lake or a neighbor, and third, from a stranger, either a hippopotamus that lives in captivity or one that resides many lakes ahead.

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(Photo: Warren Little/Getty Images)
Hippopotamuses are pictured near the 13th green in the Crocodile River which borders the Kruger National Park game reserve ahead of the Alfred Dunhill Championship at Leopard Creek Country Golf Club.

Voice Recognition

When a group heard the said sound from a neighbor or an individual of their own, they sporadically called back or lumbered in the call's direction.

Nonetheless, when the hippopotamuses heard an unfamiliar voice, they turned aggressive. The gigantic animals honked back, reached for the speaker to mark their terrain, the research team reported recently in the Current Biology journal. The animals were seen excreting and spraying feces in all directions by rotating their tails similar to propellers.

The type of voice recognition is not distinctive among gigantic animals. Elephant seals, for example, remember the rhythms and sounds of the voices of their rivals.

The new findings though could help researchers better handle populations of hippopotamuses, which are frequently relocated when they are threatened by either habitat loss or hunting.

Essentially, voices of arriving or entering animals could be played for local hippopotamuses to adapt them to their soon-to-be neighbors and lessen aggression, explained the researchers.

Stimulating a Stronger Behavioral Reaction

A related EurekAlert! report said that according to the University of Saint-Etienne, France's Nicholas Mathevon, they discovered that the vocalizations of a stranger individual encouraged or stimulated a stronger behavioral reaction compared to those generated by individuals from either the same or a neighboring group.

On top of showing that hippopotamuses are able to determine conspecifics according to vocal signatures, this research emphasizes that hippopotamus groups are territorial entities that are behaving less aggressively toward their neighbors compared to strangers.

Mathevon, together with his colleagues, are interested in bioacoustics, the study of the manner animals is exchanging information through sound.

They are particularly interested in communication networks, in which many individuals are sending and receiving information all at the same time.

Spraying Dung as a Territorial Marking Behavior

As earlier mentioned, the general intensity of the response of the hippos grew upon hearing the stranger. They were more possible to spray dung as well, which is a territorial marking behavior when they heard the sound of the hippo that was not part of their group.

Mathevon explained, when the said animals are in the water, they appeared "pretty inactive." However, such results showed that they are indeed, paying close attention to the things around them.

And, when they heard a sound or call from another hippopotamus from the shore, immediately, they responded. Mathevon elaborated, such responses to the sound signals they broadcast were quite clear, and they did not expect that.

Related information about hippo voices and sound effects is shown on Birds and Animals' YouTube video below:

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