There has been a recent paradigm shift in the study of animal communication from examining interactions as dyads to considering interactions as occurring in a communication network. The dawn chorus of songbirds, a striking acoustic phenomenon, provides an ideal opportunity to study network communication because multiple singers are within range of each other, permitting eavesdropping by both males and females. I used a 16-microphone Acoustic Location System (ALS) to simultaneously record and analyse the dawn chorus in a population of black-capped chickadees (Poecile atricapillus) breeding in eastern Ontario. Males frequency-match neighbours 24% of the time at dawn, more often than expected by chance or during daytime singing interactions. The amount of matching between males from different over-wintering flocks is significantly greater than between flockmates. Males of the same winter dominance rank match significantly more than do males of disparate ranks. Male black-capped chickadees are interacting vocally with neighbours at dawn, using the dawn chorus to mediate social relationships in ways that suggest useful information is available to the network of male and female receivers. Matching levels are not related to distance between opponents. However, males with non-fertile mates move over larger areas while chorusing and are further from their nest than males with fertile mates, suggesting dawn mate guarding. Males with non-fertile mates spend more of their chorus near boundaries with fertile neighbours than non-fertile neighbours possibly positioning themselves to facilitate eavesdropping by fertile females. Male chickadees of high and low winter social rank do not differ in either the size of their communication network, or the way they use their songs when interacting with neighbours. Males match multiple neighbours both sequentially and simultaneously. Simultaneous matching is most often the result of a former flockmate joining an interaction between two males who had been in different winter flocks. High-ranked males join the interactions of their lower-ranked flockmates, preferentially when those males are matching other high-ranked males. The dawn chorus is an interactive communication network in which all males participate and is characterized by interactions between multiple senders and receivers with males eavesdropping on interactions in which they are not involved. / Thesis (Ph.D, Biology) -- Queen's University, 2008-09-17 15:07:56.276

Black-and-white colobus monkeys are renowned for their impressive vocal behaviour, but up to date there have been only very few systematic efforts to study this. These monkeys are able to produce loud and low-pitched roars that transmit over long distances, which has lead to the assumption that these calls function in inter-group spacing and male-male competition. The fact that the monkeys sometimes produce the same calls to predators as well, has not received much attention so far. This thesis presents a detailed description of the form and function of the anti-predator behaviour of one species of black-and-white colobus monkeys, the Guereza (Colobus guereza), with a specific focus on their alarm calling behaviour. A second aim was to determine the effects of predator experience on their anti-predator behaviour, with a specific focus on call comprehension and production. Data were collected from two populations of Guereza monkeys in the Budongo Forest Reserve, Uganda, that differ in predation pressures experienced by their main predators: leopards, eagles and chimpanzees. Results showed that Guerezas use a basic form of zoo-syntax in order to compose predator-specific call sequences that vary in the number of roaring phrases and snorts. These sequences are meaningful to recipients, at least at the level of the predator class, but there were also indications for additional levels of encoded information: Guerezas appear to have evolved a second system, based on acoustic variants of individual phrases, which allows them to narrow down the information content of call sequences, generating the potential to communicate highly specific information by using a mix of syntactic and semantic cues. The monkeys’ vocal behaviour was influenced by predator experience, but not strongly so. Monkeys without prior experience with leopards lacked some of the behavioural nuances seen in leopard-experienced monkeys, but they nevertheless responded appropriately to visual and acoustic leopard models, suggesting they had retained the basic capacities to recognise this predator type as relevant and dangerous. Results are discussed in light of the comparative approach to the study of human language evolution. Although human language is unique in a number of ways, for example through its use of complex syntax and intentional semantics, some animal communication systems have revealed similar features, and Guerezas, the first member of the colobine family to be studied in this respect, are no exception. The Guerezas’ alarm calling behaviour is complex and flexible, and these monkeys have provided another piece of empirical evidence that is directly relevant for the comparative approach to human language evolution.