The Role of Experience in the Response of Fathead Minnows (Pimephales Promelas) To Skin Extract of Iowa Darters (Etheostoma Exile)
Detection of an alarm pheromone may allow conspecifics to lower their risk of predation if they avoid areas where alarm pheromones are detected. Similarly, individuals that learn to recognize and avoid alarm signals produced by heterospecifics of their prcy guild (i.e. those with which they share common predators) will likely receive similar benefits. In two separate field studies we tested whether fathead minnows (Pimephales promelas) avoid areas labelled with Iowa darter (Etheostoma exile) skin extract (which contains an alarm pheromone). One population of minnows tested was sympatric with darters while thc other was allopatric from darters. Swordtails (Xiphophorus helleri) are allopatric from fathead minnows in both of the populations tested. Swordtail skin lacks ostariophysan and darter alarm pheromones, and was used to control for a general response to damaged skin of an unfamiliar fish. In the darter-sympatric population we captured significantly fewer and smaller minnows in traps marked with darter skin extract (experimental traps) than traps marked with a control of swordtail skin extract. Given the correlation between age and size, and therefore experience, these data suggest that less experienced fish do not avoid darter skin extract to the same extent as do older more experienced fish. In the darter-allopatric population there was no difference in the number of minnows or the size of minnows captured in control versus experimental traps. Taken together, these results demonstrate that fathead minnows recognize and avoid areas where darter alarm pheromone is detected and that this is a learned response. Use of heterospecific alarm pheromones to assess predation risk may be a widespread phenomenon within communities of small fishes.