Unlike other balistids, grey triggerfish Batistes capriscus occur in social groups in subtropical reef assemblages andhave been noted to cooperate in capturing large crustacean prey. The objective of this study were to determine the structure ofdominance hierarchies of these social groups and the factors that influence hierarchies of wild-caught grey triggerfish in a naturalisticsetting. From observations of four groups of triggerfish (n - 19 fish) in both dyad and group (4-5 fish) settings, we providea description of triggerfish behaviors and coloration patterns and an explanation of the social context in which suites of behaviorsare used by dominant, middle-ranking, and subordinate fish. Sixteen behaviors and nine coloration patterns were noted forgrey triggerfish. Grey triggerfish groups form linear hierarchies in both dyads and groups as measured by Landau's Index ofLinearity (h = 1.0 for Groups 1, 3, and 4 and h = 0.95 for Group 2 in dyads; h = 1.0 for all groups in group settings). Dyadic hierarchies,however, were not necessarily good predictors of the hierarchies found in larger group settings, as they only predictedtwo of the four group hierarchies. Sex played no role in influencing status or behavior. Size had the greatest influence on dominancestatus, with larger fish being more dominant than smaller fish. An individual's dominance ranking influenced both bodycoloration and posture. These results suggest that color patterns and body postures may also be used by observers as an indicatorof an individual's social status in
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