Social living is essential for many animals, but tracking how relationships develop in a group has been difficult. To overcome this, researchers created a controlled “cave” environment for Egyptian fruit bats, in which they could continuously monitor individual bats using advanced tracking and video systems. This allowed them to follow who interacted with whom, where they spent time, and how social relationships changed over weeks and months.
HFSP Long-Term Fellowship awardee Saikat Ray, working with Nachum Ulanovsky, found that when a new group formed – or when its composition changed – the social network was initially very dynamic. Bats frequently changed their associations and interactions over the first few days. However, this instability did not last long. Within a short period, the group settled into a stable structure, where individuals maintained consistent relationships and roles. This suggests that social systems can self-organize quickly, even in complex groups.
A key feature of this stable structure was the emergence of a dominance hierarchy. Some bats became consistently higher-ranking than others, and this hierarchy influenced everyday behaviors. For example, dominant bats had better access to food and preferred sleeping spots. Once established, these dominance relationships remained stable over months, indicating that social rank is not random but becomes an enduring feature of the group.
The study also looked inside the brain to understand how these social relationships are represented. Using wireless recordings from neurons in the hippocampus (a brain region involved in spatial and social memory), the scientists discovered that some neurons track the positions of other bats relative to the individual. These “social” neurons encoded where others were relative to them, including their direction and distance, effectively mapping the social environment. This build up on the researchers’ previous study where they characterized how these neurons in the bat brains, encoded the identity of other bats, and their social relationships with them – like the sex, dominance hierarchy and social affiliation.
Overall, the study shows that social groups rapidly organize into stable structures, and that these structures are reflected in how the brain represents other individuals – linking social behavior directly to neural coding.