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, inclu..., 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), a..., Excel files, # Data for: Multiple behavioral mechanisms shape development in a highly social cichlid fish

**“Initial_Fry_StandardLength.csv”** contains the standard length (mm) of juvenile *Astatotilapia burtoni* fish at approximately 7-days post-fertilization from each brood. Juvenile fish at this early developmental stage can be called “fry.” The experimental fish were selected from these individuals (data for these experimental fish is included below in “HomeTank_Behavior.csv” and “BehAssay_Hormone_Data.csv”).

Descriptions of variables:

* *BroodNumber*:  Arbitrary number assigned to broods of fish collected on the same day at the start of the experiment. *A. burtoni* (common name Burton’s Mouthbrooder) is a mouthbrooding fish, meaning mothers will keep the developing eggs in her buccal cavity (mouth) until they are fully developed. A brood is the group of juveniles that come out one mother’s mouth.
* *StandardLength:* The standard length of the juvenile fish, measured from the tip of the jaw t...