Journal of Animal Ecology
1.Indirect interactions resulting from changes in organismal traits such as behaviour, i.e. trait-mediated indirect interactions (TMIIs), are widespread in biological communities, yet few studies have explored the potential for mutualisms to initiate TMIIs. 2.This study used a combination of behavioural observations and manipulative ﬁeld experiments to investigate potential TMIIs resulting from a mutualism between specialized cleaner ﬁsh and the‘clients’ that visit cleaners for the removal of ectoparasites. 3.Behavioural observations indicate that the bluestreak cleaner wrasse, Labroides dimidiatus, increases local predation pressure on corals at cleaner stations by attracting corallivorous butterflyﬁsh to their territories. 4. Observations of the ornate butterﬂyﬁsh, Chaetodon ornatissimus, suggest a trade-off between seeking cleaning and foraging; individuals decreased their foraging rate at cleaner stations and shifted their diet to include a greater proportion of less preferred prey items. Nonetheless, predation pressure on corals was higher at cleaner stations because the spatial response of butterﬂyﬁsh to cleaners more than compensated for their lower foraging rates. 5. The results of a ﬁeld experiment suggest that the greater predation pressure observed at cleaner stations may be sufﬁcient to reduce the growth rate of the unpreferred coral Porites rus. 6. Together, these results emphasize the need to consider mutualists as potential initiators of TMIIs and highlight the importance of integrating individual movement into conceptual analyses of TMIIs.