Social learning of predation risk and safety: fish behaviour as a model for fear recovery
As animal behaviour theory has developed over the past 70 years, much attention has gone toward social information use. Social cues in a variety of forms can be critically important in finding food and mates, in defending territories, and in avoiding predators. A wide variety of prey species are capable of learning from social information regarding predation threats, but little attention has gone toward factors that influence the acquisition of such information, how it compares to other learning mechanisms, or how prey learn socially about the absence of risk. Herein, I present research with fathead minnows, Pimephales promelas, where I first showed that learned fear responses were similar between social learning and individual learning, but socially-acquired information was more persuasive and had an overriding effect on previously learned safety. Using repeated exposures to general predation cues that lacked specific information about the predator’s identity, I induced uncertainty in naïve individuals (observers) or in knowledgeable individuals (models) within a social pairing. Repeated exposure to risk, regardless of uncertainty, promoted a high-risk phenotype that was characterized by propensity to freeze, stereotypic route-tracing, and neophobia – a phenomenon where animals show generalized fear responses toward novel stimuli. Attempting to weaken this phenotype, I paired high-risk individuals with models that were experienced with an odour as safe, but a single conditioning with one ‘safety model’ had little effect. Instead, interacting with high-risk individuals caused models to indirectly acquire the high-risk phenotype. Hence, this social transfer of information caused models to behave fearfully, making them poor demonstrators of safety. To counteract this, I used groups of calm models, or multiple, individual calm models in succession. Both strategies weakened fear in observers, as well as socially-transferred fear in models, but surprisingly this effect was much stronger among individuals exposed to risk in isolation, despite their tendency for stronger neophobia initially. While our basic knowledge of social systems has grown substantially in recent years, rarely has it been applied to human issues. My work bridges animal behaviour theory and human psychology, arguing that our understanding of predation-related fear and the information transfer in social animals can prove fruitful in understanding post-traumatic stress and behavioural therapy for its recovery.
alarm cue, fright, minnow, neophobia, PTSD
Doctor of Philosophy (Ph.D.)