Differences in timidity and escape responses between predator-naive and predator-sympatric rainbowfish populations

Responses of rainbowfish (Melanotaenia duboulayi) from two populations towards a) an active and a passive predatory fish and b) a novel trawl apparatus, were compared. Predator-sympatric fish avoided the fish predators and showed stronger avoidance behaviour in response to the active predator. These fish used predator inspection excursions to rapidly assess the potential risk and their escape responses were consistently effective. In contrast the predator-naive fish ignored the passive predator but were continually drawn towards the active predator possibly due to generalized curiosity and the absence of significant negative feedback from the predator, which was restrained by a clear Perspex partition. Despite this attraction, the predator-naive fish did not display typical predator inspection behaviour and showed very poor escape performance when initially confronted by the trawl apparatus. Many of these fish, however, showed rapid improvement in their escape performance through learning. These results suggest that predator-sympatric rainbowfish have the capacity to assess the level of threat posed by a predator and predator-naive rainbowfish learn to implement appropriate escape strategies when forced to evade a threat.