Grant E. Brown

Differential learning rates of chemical versus visual cues of a northern pike by fathead minnows in a natural habitat

We stocked 39 juvenile pike, Esox lucius, into a previously pike free pond which contained a population of approximately 78 000 fathead minnows, Pimephales promelas. Fathead minnows sampled prior to pike stocking did not show a stereotypic fright response to either visual or chemical cues from pike. After stocking pike, we sampled minnows every two days for a period of two weeks. Minnows sampled six days after stocking still did not show a fright response to the sight of a pike, but those sampled eight days after stocking did exhibit a significant fright response, indicating that acquired predator recognition based on vision occurred between six and eight days. Minnows sampled two days after stocking did not show a fright response to chemical cues of a pike. Those sampled four days after did, however, exhibit a significant fright response, indicating that acquired predator recognition based on chemical cues occurred between two and four days. These data indicate that acquired predator recognition occurs very rapidly and that the rate of learning of predator identity differs for chemical versus visual cues.

The role of experience in risk assessment: Avoidance of areas chemically labelled with fathead minnow alarm pheromone by conspecifics and heterospecifics

Abstract:In two field experiments, we investigated risk avoidance behaviour by individual fathead minnows (Pimephales promelas Rafinesque) and brook stickleback (Culaea inconstans Kirtland) in resp...

Fathead minnows use chemical cues to discriminate natural shoalmates from unfamiliar conspecifics

Naturally occurring shoals of fathead minnows (Pimephales promelas) were captured and individuals given the choice between shoalmates and unfamiliar conspecifics in a two-choice discrimination test. When presented with chemosensory cues alone or with both chemosensory and visual cues, minnows exhibited a significant preference for shoalmates versus unfamiliar conspecifics. With visual cues alone, there was no significant discrimination of shoalmates. A second set of trials was conducted to ensure that minnows were choosing natural shoalmates and not just individuals with which they were held in the laboratory. When given the choice between unfamiliar conspecifics and shoalmates from which they were separated for a minimum of two months, minnows exhibited a significant preference for shoalmates. Taken together, these data suggest that fathead minnows are able to discriminate among conspecifics on the basis of familiarity using chemosensory cues, even after a relatively long separation. The ability to discriminate among conspecifics may facilitate: (1) the maintenance of kin groups or groups that share similar foraging or predator avoidance patterns or (2) the recognition of former shoalmates after some period of separation.

Localized defecation by pike: a response to labelling by cyprinid alarm pheromone?

Fathead minnows (Pimephales promelas) that have never encountered a predatory pike (Esox lucius), are able to detect conspecific alarm pheromone in a pikes diet if the pike has recently consumed minnows. It remains unclear how this minnow alarm pheromone is secreted by pike and if a pike is able to avoid being labelled as a potential predator by localizing these cues away from its foraging range. The first experiment determined that minnow alarm pheromone is present in pike feces when pike are fed minnows. Individual fathead minnows exhibited a fright response to a stimulus of pike feces if the pike had been fed minnows, but not if the pike had been fed swordtails, which lack alarm pheromone. Individual minnows also exhibited a fright reaction to alarm pheromone in the water (which contained no feces) housing pike which had been fed minnows, suggesting that alarm pheromone is also released in urine, mucous secretions and/or via respiration. The second experiment determined that test pike spent a significantly greater proportion of time in the “home area” of the test tanks (i.e. where they were fed) but the majority of feces were deposited in the opposite end of the test tank. By localizing their defecation away from the home or foraging area, pike may be able to counter the effects of being labelled as a predator by the alarm pheromone of the prey species.

Effects of diet on localized defecation by Northern Pike,Esox lucius.

Fathead minnows (Pimephales promelas) are able to detect conspecific alarm pheromone in the feces of northern pike (Esox lucius) and have been shown to avoid areas labeled with the feces of pike that were fed minnows. The minnows did not avoid areas labeled with the feces of pike that were fed swordtails (Xiphophorous helleri), which lack ostariophysan alarm pheromone. In laboratory experiments, pike fed a diet of minnows localized their defecation away from their foraging area. It has been suggested that in doing so, pike may remove chemical cues that label their foraging area as dangerous to prey species. As yet there has been no conclusive evidence to support this hypothesis. In this experiment, we test the effects of different predator diets on localized defecation by pike. Pike were fed minnows, swordtails, or mice (Mus musculus). Swordtails and mice lack ostariophysan alarm pheromones. Area use and location of feces were recorded. Pike fed minnows spent significantly more time in the home area (i.e., area of the test tank where they were fed) and defecated significantly more often in the opposite end of the tank. Pike fed swordtails also exhibited a significant preference for the home area in area use, while those fed mice showed no such preference. When fed either swordtails or mice, there was no significant difference between the proportion of time spent and proportion of feces in each area of the test tank. These data suggest that pike localize their defecation only when consuming prey items containing alarm pheromone. The current findings support the hypothesis that pike localize their defecation to remove chemical cues from the foraging area of the home range in order to avoid chemically labeling their foraging area as dangerous to prey.