The neurobiological ecology of fear

Background/Question/Methods

Fear of predators, and predation risk, have become almost synonymous in the ecological literature.  Some authors object that referring to fear in other animals is anthropomorphic, and others object because the cognitive and emotional aspects of avoiding predation remain unknown in virtually all studies of 'the ecology of fear'.  We too object, but on the basis that failing to consider ‘fear of predators’, as a phenomenon distinct from predation risk, may be limiting our understanding of ecology.  Referring to fear when discussing predation risk in algae, for example, is evidently incongruous – having a nervous system would seem to be a minimum requirement to ‘feel’ fear.  Not only is fear something that can be measured in the brain, as has long been established, new biomedical research suggests that ‘fear of predators’ can itself be measured in the brain.  A Nature Neuroscience Review published last year documented that fear of predators is processed by a distinct neural circuit, independent of those activated by fear of an aggressive conspecific, or fear of pain.  This progress has been made in part because exposure to a predator is now the most common stressor used in studying the animal model of post-traumatic stress disorder (PTSD). 

Results/Conclusions

We will discuss the benefits and challenges of translating neurobiological findings in the lab to ecological research in the field.  Measuring fear effects in the brain can help clarify the interpretation of peripheral physiological measures like glucocorticoids levels – elevated glucocorticoids can be unambiguously attributed to predator-induced stress if accompanied by activation of the ‘fear of predators’ neural circuit.  More importantly, the fact that predator exposure can have long-lasting effects on the brain resembling those seen in PTSD patients provides a compelling link between fear of predators and likely effects of demography.  The simplest challenge to overcome is collecting brain tissue in the field.  More challenging is whether predator effects on brain activity will be identifiable, since unlike in the lab where all other stimuli are eliminated, animals in the field are subject to myriad stimuli.  Most challenging is simply where to look in the brains of species other than rats and humans.  For example, to explore the neurobiological ecology of fear in our lab, in relation to the effects we have already documented on the physiology, behaviour and demography of songbirds, we are presently at the stage of endeavouring to identify the ‘fear centre’ in the avian brain.