Temporal patterns and sex differences in dyadic interactions in a wild zebrafish population

Temporal Patterns in Interactions Across Same- and Mixed-Sex Wild Zebrafish Dyads

Animals communicate with each other through a variety of behavioral interactions, many of which are often complex due to the interplay of several ecological factors. Observations on dyadic interactions can help throw light on the more complex interactions observed among group living organisms and can help in understanding mechanisms of behaviors related to mating strategies, dominance hierarchies, and decision-making. This study focused on the assessment of several generally observed interactions among dyads of different sexes (female-female, male-male, and male-female) in wild zebrafish (Danio rerio). Temporal dynamics of these interactive behaviors were observed in 45 dyads across 3 time intervals of the day. We used generalized linear mixed models to investigate the effect of time, sex of dyad, and their interaction on specific behaviors. While the frequency of occurrence of some behaviors showed clear variation across time intervals of the day, these were further found to depend on the composition of the dyad. Contrary to previous reports, we found that same-sex dyads are equally aggressive and aggressive interactions did not vary temporally. Mating-associated interactions, as expected, were significantly higher in mixed-sex dyads and declined significantly from early morning to afternoon. Interestingly, we also found some mating-associated interactions in same-sex dyads. A fine line exists between social and mating-associated interactions in many organisms and so we speculate that these interactions could also be social interactions and not mating-related behavior. Our findings shed light on complex interactive behaviors among zebrafish, that are likely to be affected by time as well as sex composition of interacting individuals and thus has important implications for groups varying in sex ratios in the wild.

Group size and aquatic vegetation modulates male preferences for female shoals in wild zebrafish, Danio rerio

Shoaling decisions in the wild are determined by a combination of innate preferences of the individual along with the interplay of multiple ecological factors. In their natural habitat as well as in the laboratory, zebrafish is a shoaling fish. Here, we investigate the role of group size and associated vegetation in shaping shoaling preferences of wild male zebrafish. We studied the association preference of males to groups of female shoals in a multi-choice test design. We found that males made greater proportion of visits to an 8-female group compared to 2 and 4-female groups. However, males spent similar proportions of time across the three female-containing groups. When artificial vegetation was incorporated along with female number as an additional factor, we found that males prefer high and moderately vegetated patches compared to low or no-vegetation groups, irrespective of the number of females in these patches. Based on experiments using a novel multi-choice design, our results show that preference for group size can change due to interaction of two separate factors. This work is a first attempt to understand the role of aquatic flora in determining shoaling preferences in zebrafish, using an experimental paradigm consisting of a gradation in female and vegetation densities.