Effects of group size on movement patterns and clustering dynamics in rats

TL;DR

This study explores how the number of rats in an environment affects their movement and social clustering behavior.

Contribution

The study reveals how group size influences rat movement and clustering, distinguishing between statistical and social interaction effects.

Findings

Increasing rat numbers affects ambulation speed and distance traveled.

Cluster formation and duration depend on social interaction propensity.

Both statistical density and active social interactions influence clustering.

Abstract

Environment is a determining factor that can facilitate or hinder social interactions. A precursor to meaningfully engaging with conspecifics is being exposed to opportunistic encounters with others. Increasing the number of individuals in a given space (thus increasing density) would, statistically speaking, increase the likelihood of accidental encounters. This might have consequences on the formation of social networks—an idea that has not reliably been explored. If true, we would expect that increasing density would lead to an increase in the number and the duration of ‘clusters’ of animals. Here, we examined whether varying the number of rats in an open field environment differentially affected their movement dynamics or their propensity to aggregate into clusters and, if so, whether such effects are dependent solely on statistical factors due to increases in density, the potential for actively-sought social interactions, or both. We found that the number of rats in an environment impacts ambulation speed, distance traveled, cluster formation and approaches, and that number and duration of clusters are highly dependent on the propensity for the rats to engage in social interactions.

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