Data for: Multiple behavioral mechanisms shape development in a highly social cichlid fish

Early-life social experiences shape adult phenotype, yet the underlying behavioral mechanisms remain poorly understood. We manipulated early-life social experience in the highly social African cichlid fish Astatotilapia burtoni to investigate the effects on behavior and stress axis function in juveniles. Juveniles experienced different numbers of social partners in stable pairs (1 partner), stable groups (6 fish; 5 partners), and socialized pairs (a novel fish was exchanged every 5 days; 5 partners). Treatments also differed in group size (groups vs. pairs) and stability (stable vs. socialized). We then measured individual behavior and water-borne cortisol to identify effects of early-life experience. We found treatment differences in behavior across all assays: open field exploration, social cue investigation, dominant behavior, and subordinate behavior. Treatment did not affect cortisol. Principal components (PC) analysis revealed robust co-variation of behavior across contexts, including with cortisol, to form behavioral syndromes sensitive to early-life social experience. PC1 (25.1 %) differed by social partner number: juveniles with more partners (groups and socialized pairs) were more exploratory during the social cue investigation, spent less time in the territory, and were more interactive as dominants. PC5 (8.5 %) differed by stability: socialized pairs were more dominant, spent less time in and around the territory, were more socially investigative, and had lower cortisol than stable groups or pairs. Observations of the home tanks provided insights into the social experiences that may underlie these effects. These results contribute to our understanding of how early-life social experiences are accrued and exert strong, lasting effects on phenotype.

Methods
Juvenile A. burtoni body size was measured as mass (g) and standard length (mm). Length was measured at the very start of the experiment for all juveniles that could be included in the experiment. Length was measured from digital images with a ruler for scale using ImageJ. Individual identification was not feasible at this early developmental stage; therefore, these size data are not connected to behavior, hormone, or later size data. Mass and length were also measured at the end of the experiment, after the individual behavior assays. Behavior was video recorded in the home tanks and the individual behavior assays. In the home tanks, the total number of approaches, displacements, caroseling, fighting, lateral displays, entering the territory, and exiting the territory were scored using BORIS. Individual identification was not feasible in the home tanks. The individual behavior assays consisted of an open field exploration (OF), social cue investigation (SC), dominance behavior (Dom), and subordinate behavior (Sub) assays. In the OF and SC, the number of times entering each zone of the tank, and the time spent in each zone of the tank, was scored using BORIS. In the Dom and Sub assays, the number of approaches, displacements, approaches received, and submissions were scored using Solomon Coder (https://solomon.andraspeter.com/). The R package compete was used to calculate the directional consistency index (DCI) for the Dom and Sub assays, for patterns of approaching and displacing. This package was also used to calculate the dominance index David’s Score. The code was adjusted so that the calculation took both approaches and displacements into account when calculating dominance. Water-borne cortisol was collected after the behavior assays and quantified using enzyme-linked immunosorbent assays.

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Friard, O., & Gamba, M. (2016). BORIS: a free, versatile open-source event-logging software for video/audio coding and live observations. Methods in Ecology and Evolution, 7(11), 1325–1330.

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