Newborn (i.e. neonate) swordtail Xiphophorus helleri Heckel attempted to escape cannibalization attempts in a downward direction more frequently than in any other direction. The downward escape response is likely to be anti-predator behaviour. In addition, neonates were often able to escape cannibalization at the time of birth, despite no previous exposure to predators, which suggests that this anti-predator behaviour is innate. However, neonates at the time of birth were more vulnerable to cannibalism than older juveniles, which supports the hypothesis that anti-predator behaviour is, at least in part, further developed as a result of previous experience (i.e. learning).