Early recognition and response to predator, heterospecific, and conspecific visual cues by multiple species of poeciliid fry

Recognition and response to cues from conspecific and heterospecific individuals is critical to survival and reproduction and therefore should be learned early in life. Young fry of two live-bearing fishes, Poecilia mexicana and Xiphophorus birchmanni, were exposed to visual cues of three different species in order to measure shoal tightening, an antipredator defence. Both species responded to a putative predator with shoal tightening, but response to a con- and hetero-specific poeciliid did not differ, though inter-fry distances became larger in the presence of both species compared to distances prior to exposure. There were also size-dependent effects on the pairwise distance between fry. These results suggest that fry are able to learn to distinguish among species based on visual cues alone at an early age, that A. mexicanus is perceived as a threat, but that adult poeciliids are likely not perceived as a predator by fry as some studies have posited.