Data-driven modeling of group formation in the fission-fusion dynamics of Bechstein’s bats

Abstract

Communal roosting in Bechstein's bat colonies is characterized by the formation of several groups that use dierent day roosts and that regularly dissolve and re-merge (ssion-fusion dynamics). Analyzing data from two colonies of dierent size over many years, we nd that (i) the number of days bats stay in the same roost before changing follows an exponential distribution that is independent of the colony size, and (ii) the number and size of groups bats formed for roosting depend on the size of the colony such that above a critical colony size two to six groups of dierent sizes are formed. To model these two observations, we propose an agent-based model in which agents make their decisions about roosts based on both random and social inuences. For the latter, they copy the roost preference of another agent which models the transfer of the respective information. Our model is able to reproduce both the distribution of stay length in the same roost and the emergence of groups of dierent sizes dependent on the colony size. Moreover, we are able to predict the critical system size at which the formation of dierent groups emerges without global coordination. We further comment on dynamics that bridge the roosting decisions on short time scale (less than one day) with the social structures observed at long time scales (more than one year).

An agent-based algorithm resembles behaviour of tree-dwelling bats under fission–fusion dynamics

“…the ability to quickly and effectively assess trees for suitability, whereas bats without this ability instead used the tactic of eavesdropping on swarming conspecifics in large groups. Another data-driven modeling of group formation in the fission-fusion dynamics of bats worked on a system of roosts of fixed characteristics with accounted pair-specific social influence 47 . However, it is questioning how collective decision is made under variable roost conditions and unstable social relationships.…”