The role of avoidance learning in an aggressive mimicry system

Batesian mimicry systems are driven by predators that learn to associate a distinct signal with an unpalatable species and then avoid similar signals on future occasions, including those emitted by palatable mimics. Whereas many studies have investigated learning and predator memory in protective mimicry, few studies have considered learning in other mimicry systems. Aggressive mimics are defined as the resemblance of a predatory or parasitic species to another nonthreatening or even attractive species in order to approach and attack prey or to gain other benefits such as pollination or transportation. If signal receivers learn to avoid aggressive mimics and their models or learn to distinguish mimics from their models, then the success of mimics should decline. On coral reefs, juvenile bluestreak cleaner fish (Labroides dimidiatus) are aggressively mimicked by the bluestriped fangblenny (Plagiotremus rhinorhynchos). Instead of removing parasites from larger host fish, fangblennies attack reef fish and remove scales and dermal tissue. In this study, the signal receiver (a damselfish) spatially avoided cleaner fish and their associated fangblenny mimics after aggressive interactions; however, avoidance was not exhibited for longer than 24 h. Damselfish did not appear to discriminate between cleaner fish and mimic fangblenny, however, did discriminate between cleaner fish and nonmimic fangblenny. Avoidance learning was more pronounced when the fangblenny was less similar to the cleaner fish in terms of color. Finally, damselfish learnt to preempt attacks within 1 h of contact with fangblennies. This study provides important insights into the role of both spatial and preemptive avoidance learning in aggressive mimicry. Copyright 2008, Oxford University Press.