title: Cleaner wrasses Labroides dimidiatus are more cooperative in the presence of an audience.
abstract: Humans may help others even in situations where the recipient will not reciprocate [1-5]. In some cases, such behavior can be explained by the helpers increasing their image score, which will increase the probability that bystanders will help them in the future [5-7]. For other animals, the notion that many interactions take place in an environment containing an audience of eavesdropping bystanders has also been proposed to have important consequences for social behavior, including levels of cooperation [8]. However, experimental evidence is currently restricted to the demonstration that cleaner fish Labroides dimidiatus can learn to solve a foraging task [9]. The cleaners learned to feed against their preference on artificial clients if that allowed them to access additional artificial clients, which would translate into cooperatively eating ectoparasites rather than cheating by eating client mucus under natural conditions [10]. Here we show that cleaners immediately increase current levels of cooperation in the presence of bystander client reef fish. Furthermore, we find that bystanders respond to any occurrence of cleaners cheating their current client with avoidance. In conclusion, the results demonstrate, for the first time, that image scoring by an audience indeed leads to increased levels of cooperation in a nonhuman animal.
authors.affiliation: Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland. ana.pinto@unine.ch
authors.forename: Ana
authors.initials: A
authors.lastname: Pinto
authors.forename: Jennifer
authors.initials: J
authors.lastname: Oates
authors.forename: Alexandra
authors.initials: A
authors.lastname: Grutter
authors.forename: Redouan
authors.initials: R
authors.lastname: Bshary
mesh_terms: D000818:Animals; D003299:Cooperative Behavior; D005247:Feeding Behavior; D007858:Learning; D009093:Mucus; D010473:Perciformes / Q000502:physiology*; D012919:Social Behavior; D013559:Symbiosis