Hippos Will Aggressively Spray Poop at The Mere Sound of a Stranger's Wheeze Honk

The Hippopotamus is a strange beast. Although it is the third largest land mammal, it is more dangerous to humans than a grizzly bear, and we do not know much about its social communication.

A new study has found that Hippos don't like strangers and will spray the area with their feces.

The University of Saint-Etienne bioacoustician Nicolas is one of the study authors.

In addition to showing that hippos are able to identify other hippos based on vocal signatures, our study shows that Hippo groups are less aggressive toward their neighbors than toward strangers.

The team recorded calls from seven groups of Hippopotamus amphibius across three lakes in the Maputo Special Reserve. They focused on the most common noise of the Hippos, the wheeze, which can be heard over long distances.

It is difficult to study the behavioral biology of Hippos in the wild. It's difficult to identify and mark individuals and it's even more difficult to locate them. The researchers write in their paper that Hippos are solitary and feed mainly at night.

They gather in the water during the day. Hippo groups are structured around a dominant male, a variable number of females and their young, and some peripheral males. It is not clear whether individuals in a group of people form a stable group or if they move from one group to another.

After recording the calls, the researchers started playing the wheeze to see how they would react to their own group, their neighbors on the same lake, or a stranger group from a different lake.

The team found that the behavioral responses such as calling back, approaching the sound, or marking their territory by spraying poop occurred in response to all three of the sounds, but strangers incurred much higher levels of pooping.

You can see what this looks like in the video.

The team writes that marking behavior (dung spraying) is influenced by the category of the calls.

There is no significant difference between reactions to calls from the same group or from a neighboring group, while stranger group calls induce more marking than calls from an individual of the same group.

This is interesting for a number of reasons. Hippos look relaxed and focused in their watering holes, but their quick responses to calls mean they still pay attention to their surroundings.

Hippos are less aggressive to their neighbors than to strangers. Some territorial animals will be more aggressive to their neighbors than to strangers.

This might be able to help the efforts to save the Hippos.

Before relocating a group of Hippos to a new location, one precautionary measure 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.

Reciprocity, in which the animals to be moved become accustomed to the voices of their new neighbors before they arrive, could also be considered.

The research was published in a journal.