Labidochromis caeruleus cichlid preference for background colour varied between individuals and groups but did not vary for body colour of other fish

Investigations of colour-related behaviours, e.g. the context dependence of colour preferences in animal species are fundamental for understanding colour discrimination mechanisms and evolution of colour patterns. In this study, we investigated the preferences of Labidochromis caeruleus individuals or groups (three members) for both background colour and body colour of fish shoals (cichlid species with different body colours were used as stimulus shoals). Both L. caeruleus individuals and groups preferred to stay in red, blue, purple or black backgrounds as opposed to white backgrounds. However, the preference for orange backgrounds changed from nonsignificant to negative, whereas the preference for yellow or green backgrounds changed from positive to nonsignificant when the test fish changed from individuals to groups. Whether measured in individuals or groups, L. caeruleus (with yellow body colour) preferred to stay with stimulus shoals of conspecifics as opposed to cichlids with white Chindongo (Pseudotropheus) socolofi or blue Sciaenochromis fryeri body colours. However, L. caeruleus showed no preference between conspecifics and orange Metriaclima (Maylandia) estherae and preferred to stay with M. estherae as opposed other white or blue cichlid species. Furthermore, both L. caeruleus individuals and groups showed preferences for blue S. fryeri relative to white C. socolofi. Our data suggest that colour phenotypes might be an important factor for the shoal preferences of cichlids, and L. caeruleus preferentially shoals with fish exhibiting phenotypic homogeneity or being inconspicuous amongst group members. The preferences for background colour are complicated. The possible mechanism for the different responses to background colour between individuals and groups might be due to a shift in the balance between individuals and groups based on a trade-off between the requirement to avoid being detected during prey-predation interactions and maximum colour contrast in the context of resource competition or mating courtship. Further investigation of the colour preferences of both individuals and groups of cichlids with different body colours might yield interesting results.