Males show their best side revisited : Effects of predation pressure on laterality in wild guppies

The ability to detect and avoid predators has been suggested as one of the main drivers for behavioral lateralization. This is supported by studies reporting that animals from high-predation environments are more lateralized than those from low-predation environments. Some studies, however, have shown no effect of predator regime on lateralization. Lateralized behavior can also be driven by phenotypic asymmetry, where the more attractive side of the body is preferentially displayed during male-female interaction and courtship. The importance of fluctuating asymmetry for mate choice has been highly debated for a number of reasons. Here, we revisited the concepts of predator-induced behavioral lateralization and phenotypic asymmetry using wild Trinidadian guppies Poecilia reticulata from three different stream systems. Using fish collected from both high- and low-predation environments, we quantified behavioral lateralization in terms of directional turning bias, measured right-left body color asymmetry, and investigated whether a male side-showing preference was present in male-female interaction trials. We found that guppies were, at best, moderately lateralized on average (across all populations), without any general effect of predator regime. There were some slight stream-dependent side biases in color asymmetry, but this did not translate into a side-showing preference in any of the populations in the interaction trials. Some significant observed effects align with previously published results, but these were dependent on stream-origin and were not repeated across different experiments, complicating interpretation. We conclude that when investigating the effects of predation regime in general, and such effects on behavioral lateralization or fluctuating asymmetry in particular, attention must be focused toward several factors such as experimental assay used and population origin, and broad generalizations from results stemming from experiments including only one population should be avoided