GENERALIZATION OF PREDATOR RECOGNITION IN FATHEAD MINNOWS: IMPLICATIONS FOR RESPONSES TO INTRODUCED AND HYBRID PREDATORS

Abstract

To survive, prey must recognize predators and appropriately respond to the associated risk. Some prey must first gain this information through experience. Naïve fathead minnows (Pimephales promelas) learn to recognize a predator after a single learning event, and subsequently generalize their antipredator responses to odours of novel, closely-related predators. This phenomenon known as ‘generalization of predator recognition’ has been observed in fishes, amphibians, reptiles, and mammals via generalization of both olfactory and visual cues. The extent of generalized predator recognition has been a topic of interest for researchers over the past 10 years, providing a wider expanse of knowledge that has begun to uncover the circumstances facilitating generalization and those that do not. The overall purpose of my research was to explore one aspect that has received minimal attention—the ability for prey to generalize response to frequently stocked hybrid predators. I first investigated the capacity for minnows to generalize to hybrid tiger trout odour after alarm-cue learning of either one or both of the parental species’ odours. My results in Chapter 2 showed that regardless of conditioning odours, minnows were able to generalize their antipredator response from the known parental species to the novel hybrid predator and to the novel confamiliar parental species. Following the results of Chapter 2, I was interested in understanding whether knowledge of parental species was important for hybrid tiger trout recognition or if knowledge of any trout would be conducive to facilitating generalized predator recognition of tiger trout odour. Chapter 3 was designed to investigate this question. Results from this experiment reinforced that knowledge of one or both parental species would be necessary for adequate generalization of hybrid predator odours. Minnows conditioned to learn a confamiliar species to both parental trout did not respond to the odour of novel tiger trout. Results of both experiments were also analyzed to observe the intensity of antipredator response over the eight-minute post-stimulus observation. These analyses indicated that prey may indeed exhibit graded antipredator responses based on the degree of phylogenetic similarity between the known and novel predators, evidence of which may be concealed when observing only the overall response to novel odours. With the increasing prevalence of ecological invasions and continued introduction of fish species into aquatic habitats, knowledge of how prey will respond to novel species may illuminate how susceptible populations and ecosystems may be. My results highlight the importance of accounting for lake and stream composition and the level of prey naïvety prior to introducing hybrid predators.