Introduction

Animal societies are structured by behavioural events that influence interactions between individuals and their environment. Visual, acoustic and chemical cues are important in signalling a variety of social cues such as readiness to mate, agonistic interactions and position in a hierarchy. Social mammals, such as cetaceans, have a complex social structure that primarily uses visual and acoustic cues to govern interactions between individuals. Whitehead (2007) hypothesized that long-lived animals that are dependent on other populations to survive, and are exposed to greater environmental variation over longer time scales, will develop social learning strategies. This is particularly likely in the marine environment with top predators such as cetaceans. It is challenging to understand cetacean behaviour as the animals spend considerable periods of time below the sea surface, but research with good experimental design, that uses systematic methods and hypothesis testing, can answer questions about cetacean behaviour and in turn the effects of human activities on cetaceans (Mann, 1999; Bejder & Samuels, 2003).

As a result of longitudinal studies, in many cases now spanning in excess of 25 years – for example on Shark Bay, Western Australia and Sarasota Bay, Florida bottlenose dolphins (Tursiops spp.), killer whales (Orcinus orca) in British Columbia, Canada and humpback whales (Megaptera novaeangliae) in the USA – we now have an understanding of the roles of males and females in mating behaviour and the rearing of offspring (Mann et al., 2000). The long period of maternal dependency in odontocetes, in particular, appears to largely serve as time to learn how to function in their complex society (Whitehead & Mann, 2000). This learning can involve horizontal transmission from mother to calf but also vertical transmission through interaction with other individuals in the population. The period of calf dependency varies considerably in cetaceans, with baleen whale calves weaned at around six months of age and odontocetes weaned from eight months to six years of age, although there are of course exceptions to these (Whitehead & Mann, 2000). The period of calf dependency appears to be linked to the social complexity of the species, with more solitary animals exhibiting high levels of group fission–fusion and generally having shorter periods of calf dependency. For migratory whales we know that calves learn their migratory patterns from their mothers and these are timed with environmental changes on the feeding and breeding grounds (Bannister, 2009).