Abstract
Understanding reproductive behaviour, particularly courtship and mate selection, is crucial in the conservation management of the globally endangered basking shark (Cetorhinus maximus). Currently, there is very limited knowledge of their life history, including their reproductive behaviour. This study aimed to elaborate on their recently described courtship behaviour off the west coast of Ireland where several aggregations of these sharks have been documented using aerial and underwater recordings. They are observed performing synchronized swimming patterns in a slow-moving, circular formation known as a ‘torus’ and can be seen engaging in close-following and interaction behaviours. Differences in behavioural tendencies were observed depending on the size of the group and the composition of the individuals participating. Sharks involved in larger torus formations tended to exhibit more energetic and dynamic movement than those observed in smaller group formations. Body size and male-to-female sex ratio may also appear to influence the level of interaction and movement within these courtship constructions, though further investigation is required. This unique and rare event emphasizes the critical habitat of the northeast Atlantic for these endangered species and requires further monitoring and exploration.
Key Words: Behaviour, conservation, courtship, elasmobranch, ethology
