Collective responses to acoustic threat information in jackdaws.
Woods, Richard David
Thesis or dissertation
University of Exeter
Navigating the physical world may present only a small fraction of the challenges faced by social animals. Sociality brings with it numerous benefits, including access to important information that may have otherwise been harder to come by. However, almost every aspect of these apparent benefits may also entail additional cognitive challenges, including how to interpret signals from conspecifics, who to attend to, and how to incorporate knowledge about signallers when deciding how to respond. One approach to understanding the cognitive abilities associated with social function is to investigate social species that take part in potentially costly group behaviours, where individual decisions must be made in a social context. In this thesis I explore how jackdaws (Corvus monedula), a highly sociable corvid species, use acoustic information to coordinate collective anti-predator responses. In Chapter Two I showed using playback experiments that the magnitude of collective responses to anti-predator recruitment calls known as “scolding” calls depends on the identity of the caller, with larger responses to familiar colony members than unfamiliar individuals. In Chapter Three I then used habituation-dishabituation experiments to show that this vocal discrimination operates at the level of the individual, with jackdaws discriminating between the calls of different conspecifics, regardless of their level of familiarity. In Chapter Four, I examined whether aspects of call structure conveyed information about threat levels. Here, I found that high rates of scolding calls were associated with elevated threats, and playback experiments suggested that this information might result in larger group responses. The finding that jackdaws are capable of mediating their response to alarm calls based on the identity of the individual caller, and on structural variation in call production, raised the question of whether jackdaws employed similar forms discrimination between acoustic cues made by predators in their environment. I investigated this in Chapter Five, using playback experiments to show that jackdaws responded not only to the vocalisations of resident predators, but that this ability extended to novel predators, and that responsiveness was mediated by the phase of the breeding season in which predators were heard. Together, these findings provide insights in to how discrimination among acoustic cues can mediate group behaviour in species that respond collectively to threats.
Natural Environment Research Council
PhD in Biological Sciences