Lionesses use licking to strengthen social bonds.
Lions nuzzle their pride members not just to look cute, but also to strengthen social bonds, according to a new study of this adorable behavior.

In the study, published Sept. 5 in PLOS ONE, researcher Tomoyuki Matoba, of the University of Tokyo, watched a group of captive lions at the Tama Zoological Park in Tokyo. He saw they used head rubbing and licking to reinforce bonds with pride members.

This behavior is interesting, because other animals — even similar predatory, group-living mammals like cheetahs — bond using different social interactions. For example, the spotted hyena exposes its genitals when it meets other members in its group.

The researchers think the lions may use head rubbing as a way to create a group odor, which is a "result from a shared bacterial community of the members, mediated by coexistence in the same space, frequent bodily contact and/or consistent scent marking of the same sites," they write in the paper.

While the scientists watched, they saw that cuddles were regularly exchanged within the observed group, but males and females seemed to prefer different methods for showing their affection.

Males typically rely on head rubbing.
Male lions used head rubbing when interacting with other males, while females mostly used licking. Females were observed using head rubs, but mainly when interacting with males. Maternal instinct may explain why lionesses are more likely to use licking than males.

The observed lions chose a snuggling partner based on kinship and age. Lions were more likely to interact with each other if they were closely related or about the same age.

Male lions in the wild must form coalitions with other males to protect territory and mating rights, according to a PLOS ONE community blog post. This may explain why male to male head rubbing was the most commonly observed lion-on-lion snuggle: Establishing and maintaining social bonds is vital for males.