Preschool for small frys: threat-sensitive learning of predators by embryonic fathead minnows

Abstract

Predator avoidance often comes at the cost of reduced foraging and mating opportunities, and therefore, prey animals are often highly attuned to variation in risk. Indeed, individuals capable of detecting threats early in life are at an advantage because they may be better able to escape risks than their naïve peers. Some prey organisms, including embryonic prey, can learn to recognize new predators and may even incorporate information on the degree of threat involved. Prey organisms that evaluate the intensity of a threat and modify their behaviours accordingly should have a distinct advantage by being able to seize opportunities in low-risk situations. Graded behavioural responses that vary depending on threat levels are referred to as threat sensitive. Here we show that embryonic minnows are not only capable of learning to recognize novel predators, but do so in a threat-sensitive manner, such that fish responded with an intensity correlated to the degree of the threat to which they were exposed in the egg. Subsequent to embryonic exposure to one of three different concentrations of alarm cue paired with a novel predator odour, juvenile fish from all three groups responded to predator odour by reducing their movement. However, only those exposed to the pairing with the highest concentration of alarm cue later increased their shelter use. These responses were maintained over the course of 10 months. • Embryonic fathead minnows can learn to recognize predators. • Minnows modify behaviour based on intensity of threat learned as embryos. • Embryonic minnows do not ‘forget’ learned predators for at least 10 months.