Mouses use chemical clues such as smells to feel social hierarchy, study results

Researchers from the Francis Crick Institute have shown that mice use chemical clues, including odors, to detect the social rank of an unknown mouse and compare it to theirs, using this information to determine their behavior.

Like many mammals, mice live in a social hierarchy where some are more dominant than others. This helps to avoid conflicts and establish breeding partners.

It was previously suggested that some mice could display fixed behavior, regardless of whom they interact, or that physical properties can give clues to the social classification. However, new research published today in Current biology shows that mice rather deduce a rank of mice unknown by chemical signals transmitted in the air (odors) or by direct contact (non -volatile perfume signals).

The Crick team has set this using a test where male mice enter a transparent tube at the opposite ends, meeting in the middle. In this type of confrontation, a more subject animal will generally be withdrawn.

The researchers first examined interactions in mice who shared the same cage, using this to classify each mouse on a hierarchy, before observing how the mice responded to a set of unknown opponents.

They found that foreigners could recognize the rank of the other, compare it to their own and withdraw or force the other mouse to withdraw.

The team then tested the mice in the dark, noting that this did not affect recognition of the rank, suggesting that signals such as physical size or behavior do not determine the recognition of a more aggressive opponent. Likewise, casting the mice to eliminate their sex hormones had no impact.

Finally, the team has experimentally blocked the two chemiosensory systems that mice use – one for odors in the air (olfactory system) and one for chemical signals transmitted by physical contact (vomeronasal system).

They found no effect when only one of these systems has been deleted; The two had to be ablated before the mice could recognize the rank of opponents. This has shown that mice use olfactory and vomeronasal systems to recognize rank and can compensate if we are missing.

Like mice, people can also deduce the social status of others around them compared to their own, also using sensory clues, including language, facial expression or clothes.

The next step for researchers is to study the fields of the brain information on the rank of opponents and their own rank and make a decision of withdrawal or progression.

Neven Borak, former doctorate. The student of the neuronal treatment laboratory dependent on the state in Crick and the first author, said: “We have shown that mice weighed strangers using chemical clues and can detect social status without needing a long history of confrontations with these specific adversaries. It is a fascinating phenomenon that humans do too mainly using the visual indices.

“Our work offers an interesting perspective on social mobility: humans, such as mice, can enter a new group of people, but maintain an understanding of their own social rank and assess the social status of unknown people.”

Jonny Kohl, group leader of the neuronal treatment laboratory dependent on the state in crick and principal author, said: “We have shown for the first time how mice integrate internal and external information on domination.

The neuronal treatment laboratory dependent on the state studies how brain processes are affected by the state of the body. By studying how physiological states, such as pregnancy, stress or sleep, have an impact on neural circuits in mice, researchers hope to advance a more integrative vision of brain physiology in health and sickness.