Female Bechstein’s Bats Adjust Their Group Decisions about Communal Roosts to the Level of Conflict of Interests

Abstract

Most social animals depend on group decisions for coordination. Recent models suggest that the level of interindividual conflict strongly influences whether groups reach a consensus during decision making. However, few experimental studies have explored how wild animals make group decisions in situations with conflicting interests. Such experimental data are particularly lacking for animal societies with regular fission and fusion of subgroups. In this long-term study, we varied the level of conflict of interest among members of three wild Bechstein's bat (Myotis bechsteinii) colonies with high fission-fusion dynamics experimentally to explore whether the bats adapt their group decisions about communal roosts accordingly. In situations with low levels of conflict of interest, a minority of bats experiencing a roost as suitable was sufficient for a group consensus to use it communally. In contrast, if their interests diverged strongly, the bats no longer sought a compromise, but based their roosting decisions on individual preferences instead. Our results demonstrate that the rules applied to make group decisions can vary with the level of conflict among the individual interests of group members. Our findings are in agreement with predictions of the models and provide evidence for highly flexible group decisions within species.

How collective comparisons emerge without individual comparisons of the options

“…Using individual tagging to manipulate, the information available to certain animals is a powerful tool in understanding the mechanisms of collective decision-making [22,23]. We presented ant colonies ( Temnothorax albipennis ) with a choice between two new nests: one good and one poor.…”

Consensus costs and conflict in a collective movement

“…Compromise is a common means of resolving conflict, especially for "when" decisions, but, as noted above, it frequently is not a viable option, such as in "where" decisions. When consensus costs are low, compromise is frequently chosen as an acceptable outcome, even if the decision is favored by a minority [23]. However, when consensus costs are high, compromise is avoided.…”

Principles and Patterns of Bat Movements: From Aerodynamics to Ecology

“…To achieve coordination, the individuals involved need to transfer information to one another about their position and their activities and intentions. In bats, information transfer has been shown to help colony members to coordinate roosting behavior (Kerth and Reckardt 2003;Kerth et al 2006;Fleischmann et al 2013) and group foraging (Wilkinson 1992;Dechmann et al 2009;Cvikel et al 2015a). In some of these species, communal roosts serve as centers where colony members exchange information about resources (e.g., Wilkinson 1992) but bats can also benefit from social information outside the colony when on the wing (Wilkinson 1992;Dechmann et al 2009;Cvikel et al 2015a).…”

“…During roost switching in Bechstein's bats (Myotis bechsteinii), the level of conflict among colony members about the suitability of a given potential roost strongly influenced whether a consensus about communal roosting is reached. If the experimentally induced conflict of interests became too strong, the colony temporarily formed subgroups that reflected the individual interests of the bats roosting together (Kerth et al 2006;Fleischmann et al 2013). In contrast, brown long-eared bats (Plecotus auritus) that experienced the same high level of conflict of interest always achieved a colony-wide consensus about communal roosts (Fleischmannand Kerth 2014).…”