Effects of predation pressure on the cognitive ability of the poeciliid Brachyraphis episcopi

Variable levels of predation pressure are known to have significant impacts on the evolutionary ecology of different populations and can affect life-history traits, behavior, and morphology. To date, no studies have directly investigated the impact of predation pressure on cognitive ability. Here we use a system of replicate rivers, each with sites of high- and low-predation pressure, to investigate how this ecological variable affects learning ability in a tropical poeciliid, Brachyraphis episcopi. We used a spatial task to assess the cognitive ability of eight populations from four independent streams (four high- and four low-predation populations). The fish were required to locate a foraging patch in one of four compartments by utilizing spatial cues. Fish from areas of low-predation pressure had shorter foraging latencies, entered fewer compartments before discovering the reward patch and navigated more actively within the maze, than fish from high-predation sites. The difference in performance is discussed with reference to forage patch predictability, inter- and intraspecific foraging competition, geographic variation in predation pressure, boldness-shyness traits, and brain lateralization.