Hyenas greet friends to reinforce social bonds: Study

London -  A new research has revealed that the very sociable spotted hyenas engage in greeting ceremonies to reinforce social bonds and form a coalition.

Female hyenas usually carry out greeting ceremonies by standing side by side and sniffing each other before embarking on a group task.

This appears to reinforce social bonds before a potentially risky activity, such as a hunting trip or an attack on an enemy predator.

Researchers, led by Jennifer Smith from the University of California- Los Angeles, studied adult female spotted hyenas, Crocuta crocuta, in a large female-dominated social group in Kenya.

Prof Kay Holekamp from the Michigan State University, who also took part in the study, said that the animals, also known as laughing hyenas, live in 'fission-fusion' societies.

"They live at the top of a food pyramid, so there's a lot of competition for food and they often separate to hunt," she told the BBC News.

"So they're on their own a lot, but they come together when they need to form a coalition - to defend their territory, for instance," she added.

This constant wandering and returning is key to why greetings are so important to the animals.

The rather intimate sniffing will be a familiar sight for any dog-owner.

But for hyenas, a very unusual feature of their anatomy is involved in these ceremonies.

Females, which are considerably larger and socially more dominant than males, have enlarged penis-like genitalia.

This pseudo-penis becomes enlarged when the animals are 'socially excited'.

"Previously, scientists thought that an erect phallus was a sort of flag of submission to another hyena," said Holekamp.

But she and her team have now found that this excitement and the subsequent ceremonious sniffing were a way for the animals to gather support.

"We saw them engage in these greeting ceremonies and then form a coalition to mob a lion," said Holekamp.

Trying to scare away another top predator in this way is very risky, and the greetings appear to 'get all the animals on the same emotional plain', she said.

The findings are reported in the journal Animal Behaviour.