Examining behavioral interactions between non-native predators and native prey: A tale of two cichlids

Predation is a major mechanism underlying impact by non-indigenous species. Susceptibility of native species to predation by a non-indigenous species should intimately relate to the level of prey naiveté toward predators. Non-indigenous species  predate opportunistically on naive prey that have no common evolutionary history with the non-indigenous predator, and thus lack antipredator responses or show behavioral responses that are ineffective against novel predation. If invading predators are somewhat similar to native species or to invaders prey are already familiar with, prey may respond adaptively to novel predation risk, and thus predator impacts could be relatively small.  To address these issues, we examined the predatory effect of two introduced cichlid species on Everglades freshwater prey assemblages. At least 14 non-indigenous fish species are presently established in the Everglades, most of them the result of releases of tropical ornamental species into urban canals. One of the most recent invasions has been the arrival of the African jewel cichlid Hemichromis letourneuxi. Other cichlid species, including the abundant Mayan cichlid, Cichlasoma urophthalmus, have been present in the system for several decades. We compared the anti-predator behavior by native prey to the two cichlid predators, namely activity and refuge use. To examine the role of experience and prey naiveté on antipredator behavior, we used prey from two different populations: one exposed to Mayan cichlid predators only and one exposed to both predators. Prey included several common forage fish species in Everglades marshes, which appear to be readily consumed by both predators. Results showed that the antipredator response of prey to the novel predation risk posed by jewels was rather similar to that shown to Mayan cichlids for exposed populations, suggesting that predators can be equally risky. In contrast, naïve populations showed little response to novel jewel predators.