WikiFindings

Bat groups are willing to split up rather than everyone go with the majority decision

Background

Groups of animals must agree on their choice of options if they are to stay together. For example, to roost together during the day bats must agree on a roosting site (e.g. bat box). Many types of animal groups must stay together (e.g. honeybees) so often take the majority option. But many animals, such as bats, live in groups that often split up and reform. When making group decisions they have more options: only make a choice that everyone agree with, or split up so everyone gets their preference. For example, bat groups can split into two groups in separate roosting sites for a few days before reforming when a different roost site is found that everyone likes.

Findings

We carried out experiments with bat boxes that gave individuals conflicting information: some individuals found that bat boxes were suitable for roosting, whereas others found that the same boxes were blocked by wire mesh. This did not significantly the number of days that the boxes were used by any bats. Instead, fewer bats were seen in these boxes. A second experiment gave some individuals experience of noisy disturbance when in a box. If a bigger proportion of bats experienced the noise, fewer bats returned. However, disturbed bats returned if the majority were not disturbed.

Implications

The bats considered their own information and the behaviour of their colony mates when deciding what to do. Clearly, bats do not find a choice that works for everyone, but instead are happy to split up temporarily. However, there were effects of majority decisions, since individuals sometimes went with the majority even if they had a different preference. Overall the data shows that most individuals are involved in decisions, in contract to honeybees in which a few scouts make decisions, and elephants and orca where dominant females lead. It is clear that group decision-making has evolved differences among species that depend on their ecology and relatedness.