Indirect and Transgenerational Effects of Predation Risk: Predator Odour and Alarm Pheromones in the Bank Vole

Abstract

Predator-prey interactions are a major evolutionary driver, affecting not only the direct mortality of prey species, but also their behaviours and reproduction. Prey species behavioural adaptations aim to mitigate the effects of predation and to maximise survival and individual fitness. These adaptations include the ability to signal a threat to conspecifics, e.g. via alarm calls or alarm secretions, or to detect predator presence via odours. In this thesis, I studied the effects of predator odours and conspecific alarm secretions on behaviour and reproduction bank voles (Myodes glareolus), a small mammal species inhabiting boreal forests. My work focused on three major points in comparing the direct predator cue and indirect conspecific cue: first, how the reproductive behaviour is affected by the predator odour or alarm pheromone, second, whether there are transgenerational effects and how they are exhibited in offspring, and third, what the chemical nature of these alarm secretions is. I conducted four experiments, which included both trials in semi-natural enclosures and under controlled laboratory conditions. I found evidence that exposure to conspecific alarm secretions causes a shift in voles’ reproductive behaviour, switching towards terminal investment. This became apparent with an increase in parturitions and an increased growth rate in larger litters, which did not occur when exposed to predator odour. I also found evidence of transgenerational effects, which affect aspects of the offspring’s exploratory and foraging behaviour. Additionally, I discovered that these behavioural effects are context-dependent and do not occur in every environment. Lastly, I identified a group of chemicals from voles’ alarm secretion, which are likely to be responsible for the observed effects. The results of my thesis fill a knowledge gap concerning chemical communication in mammals, and help to further understand the implications of predator presence on prey behaviour and reproduction. Keywords: Behaviour; chemical communication; cross-generational effect; fear effect; predator-prey-interaction; terminal investment.