Cleaner wrasse are capable of calming large predators by caressing them, according a study published in the most recent issue of the journal Behavioral Ecology.
The study by Karen Cheney, Redouan Bshary, and Alexandra S. Grutter built miniature coral reefs in aquaria and observed the interactions between Cleaner wrasse (Labroides dimidiatus), their predatory and non-predatory clients and potential prey species that were not clients of the Cleaners.
The authors found that the predatory fishes spent significantly less time (by up to half) chasing potential prey species when the Cleaner wrasse was present, even when the predatory fish was not being groomed.
Cleaner wrasse use tactile stimulation as a preconflict management strategy to reduce and possibly eliminate predation risk from its clients.
This tactile stimulation involves the Cleaner wrasse hovering near the client fish and touching the client with the Cleaner s pectoral and pelvic fins.
The authors found that the more the cleaner wrasse touched client predatory fishes, the less time they spend chasing potential prey species.
The authors hypothesize that reduction in aggression by predators at cleaning stations may not only act as an indirect benefit to potential prey at cleaning stations but also modify the community in positive ways that could loop back to benefit the Cleaners. For example, Cleaners may directly benefit from a calmer environment resulting in longer cleaning interactions and increased number of clients to cleaning stations.
For more information, see the paper: Cheney, KL, R Bshary and AS Grutter (2008) Cleaner fish cause predators to reduce aggression toward bystanders at cleaning stations. Behavioral Ecology 19, pp. 1063"1067.