Biting cleaner fish use altruism to deceive image–scoring client reef fish

Abstract

Humans are more likely to help those who they have observed helping others previously. Individuals may thus benefit from being altruistic without direct reciprocity of recipients but due to gains in 'image' and associated indirect reciprocity. I suggest, however, that image-scoring individuals may be exploitable by cheaters if pay-offs vary between interactions. I illustrate this point with data on cleaner-client reef fish interactions. I show the following: (i) there is strong variation between cleaners with respect to cheating of clients (i.e. feeding on client tissue instead of parasites); (ii) clients approach cleaners, that they observe cooperating with their current client and avoid cleaners that they observe cheating; (iii) cleaners that cheat frequently are avoided more frequently than more cooperative cleaners; (iv) cleaners that cheat frequently behave altruistically towards their smallest client species; (v) altruistic acts are followed by exploitative interactions. Thus, it appears that cleaners indeed have an image score, which selects for cooperative cleaners. However, cheating cleaners use altruism in potentially low-pay-off interactions to deceive and attract image-scoring clients that will be exploited.

Reputation and the evolution of cooperation in sizable groups

“…Moreover, observation by bystanders is an important factor of reputation. Several studies have demonstrated that observation by bystanders strongly influences some kinds of animals' behaviour (Oliveira et al 1998;Doutrelant et al 2001;Bshary 2002).…”

On the further integration of cooperative breeding and cooperation theory

“…However, signal reliability may not necessarily be based on genetic quality. Client fish, for instance, base their decision about whether to interact with a particular cleaner on the service quality they observed in a previous interaction of the cleaner with another client (Bshary, 2002;Bshary and Grutter, 2006). Apparently, the current behaviour of the cleaner predicts to a certain extent how cooperative the following interaction will be, therefore eavesdropping on the interactions of others appears to contain reliable information for clients (Covas et al, 2007).…”

“…Apparently, the current behaviour of the cleaner predicts to a certain extent how cooperative the following interaction will be, therefore eavesdropping on the interactions of others appears to contain reliable information for clients (Covas et al, 2007). Cleaners, in turn, can make use of an eavesdropping audience to signal their (short term) quality as cleaner (Bshary and Würth, 2001;Bshary, 2002;Bshary and D'Souza, 2004;Bshary and Grutter, 2006). Signal reliability is central for prestige based explanations of cooperative investment and it remains a challenging question to determine under which conditions signal reliability can evolve (see also Covas et al, 2007) so prestige can be an explanation of helping behaviour.…”

The evolution of judgement bias in indirect reciprocity

“…We expect judgement bias to evolve in any organism that exhibits image scoring, whether that be cleaner fish (Bshary 2002;Bshary & Grutter 2006) or humans ( Wedekind & Milinski 2000;Wedekind & Braithwaite 2002). Repeated interactions between the same individuals are not necessary for indirect reciprocity and judgement bias to evolve.…”