Social organisation, social behaviour and collective movements in reef manta rays

Obtaining data on elasmobranch movements and behaviours in marine environments is a considerable challenge, but is urgently required to implement species management plans. It is important to understand patterns and mechanisms of group formation and cohesion, including social organisation and collective behaviour, that are likely to be adapted to current selective environments. These are key aspects of animal behaviour and behavioural ecology that influence population structuring. Reef manta rays (Mobula alfredi) are large and mobile pelagic elasmobranchs that occupy subtropical coastal areas in proximity to developing human populations. They form groups at shallow water aggregation sites, where they are vulnerable to exploitation and disturbance. In this thesis I show that M. alfredi: a) have structured societies with active social preferences between individuals, linked to site attachment; b) have strong behavioural heterogeneity that influences social dynamics; c) make gestural movements that may be a form of social communication; and d) alter their collective movements during foraging and courtship events. Our results suggest that conservation strategies should consider the social organisation and social behaviours of manta rays to better understand their spatial ecology and evolutionary dynamics, predict the impact of exploitation by fisheries, and mitigate disturbance from marine ecotourism. Local measures that consider groups as complex structures resulting from interactions between heterogenous individuals are likely to be most useful for ongoing management -- abstract.