Factors Influencing the Establishment of Dominance Hierarchies of the Grey Triggerfish (Balistes capriscus)




Cleveland, David W.

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The grey triggerfish {Batistes capriscus) is a common species in Atlantic sub-tropical waters. Little is known about the behavior of this species, other than feeding habits. The primary objectives of this study were to determine the factors influencing the social hierarchy of wild-caught grey triggerfish in a captive, but naturalistic, setting. From observations of four groups of triggerfish (N = 19 fish), I provide a description of triggerfish behaviors and coloration patterns, and an explanation of the social context in which suites of behaviors are used by dominant, middle-ranking, and subordinate fish. Specific objectives addressed were: (1) What is the dominance structure of a triggerfish group and what factors affect its establishment? Is the hierarchy linear or circular, and what are the direct consequences of the hierarchy on individuals? (2) Does the size and/or sex of the fish influence the dominance status? (3) Is the group dominance structure related to the dominance status of an individual within a dyad? Sixteen behaviors and nine coloration patterns were described for the grey triggerfish. These behaviors were categorized into dominant, subordinate and neutral behaviors, and their frequency was used to score the fish for dominance hierarchy matrices. Grey triggerfish groups formed linear hierarchies as measured by Landau’s Index of Linearity (h = 1.0 for groups 1, 3, & 4 and h = 0.95 for group 2 in dyads; h = 1.0 for all groups in group settings). Dyadic hierarchies, however, are not necessarily good predictors of the hierarchies in group settings, as they only predicted 2 of the 4 group hierarchies. In the two hierarchies that were not predicted from the dyad results, both dominant and subordinate animals switched ranks. As for the factors influencing the formation of the hierarchy structure, size is the greatest influence on the highest ranking fish (alpha), (dyads R2 = 0.72, p = 0.0001, groups R2 = 0.59, p = 0.0001) while an individual’s ranking influences body colorations and postures. Sex played no role in influencing status or behavior. Dominant fish displayed Approach and Pass behaviors more frequently than middle-ranking or subordinate fish (p = 0.0001, and p = 0.006, respectively). Trigger up and Head down behaviors were more frequently displayed by middle-ranking and subordinate fish than dominant fish (Bonferroni-Dunn, p = 0.038 and p = 0.0001, respectively). Coloration patterns were not independent of fish rank, with dominant fish using a Light banding pattern most often and middle-ranking and subordinate fish using it infrequently (2-factor ANOVA, p = 0.008, Bonferroni-Dunn, p = 0.045 and p = 0.006, respectively). Subordinate fish most often displayed Grey coloration (Bonferroni-Dunn, p = 0.022), while dominant fish never displayed Grey.



Balistidae, hierarchies


Cleveland, D. W. (2002). Factors influencing the establishment of dominance hierarchies of the grey triggerfish (Balistes capriscus) (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.


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