Lateralisation and sociability under natural and experimental predation pressure in the Trinidadian guppy (Poecilia reticulata)

Predators impose a strong selective pressure on the behavioural traits of prey species. Group living, or sociability, allows individuals to reduce their own risk of predation through avoidance, dilution, and confusion effects. Another potentially beneficial mechanism is behavioural lateralisation, or “handedness”, the asymmetrical expression of cognitive brain functions through a directional bias in visual or motor tasks. In my thesis, I explore the interaction between behavioural lateralisation, sociability, and predation in both natural and captive populations of Trinidadian guppies (Poecilia reticulata). In Chapter Two, I examine the consistency between current behavioural lateralisation methodologies and assess the assumptions behind these methods, including the number of incorporated turn choices and the impact of random chance. In Chapter Three, I present the use of environmental DNA in assessing natural piscine guppy predator communities at six sites across the Northern Range of Trinidad. Using this measure of predation, I assess its viability in predicting differentiation of adaptive anti-predatory behaviours in natural guppies, including sociability, activity, and both visual and motor lateralisation. In Chapter Four, I assess the visual lateralisation of guppies tested either solitarily or in groups in the presence or absence of a live predator, the blue acara (Andinoacara pulcher). Using a repeated measures design, I investigate the repeatability of guppies’ visual lateralisation in terms of personality variation across the investigated contexts. In Chapter Five, I assess the visual lateralisation of natural guppies when viewing a social stimulus and their sociability across a gradient of predation risk using nineteen sites in the Northern Range of Trinidad. Overall, my research demonstrates relatively low levels of lateralisation throughout contexts and populations. However, subtle trends in the lateralisation of eye-use when viewing a predatory or social stimulus appear to exist in relation to predation risk, with an apparent social conformity in lateralisation when assessed in groups.