Body slap: An innovative aggressive display by breeding male gray seals (Halichoerus grypus)

Aggressive interactions between male grey seals during the breeding season are characterized by pre-escalation threat displays. Typical grey seal threat behaviours involve cephalic displays of gape, head position or proximity. In fall of 2011, extensive research on an expanding grey seal breeding colony on the English mainland identified a unique behaviour of ‘body slapping’ utilized by males in the pre-fight displays. As the body slap has only been seen at Donna Nook and the north Norfolk colonies in the UK, the aims of this study were to describe the behaviour and begin to elucidate the signal’s meaning. To do this we first examined when and where it is performed. Furthermore, to test if the behaviour is one of submission or aggression we examined its association with subsequent winners or losers, if dominance influences rate of display, and how the behaviour is associated with other aggressive behaviours. Results indicate the body slap display at Donna Nook is performed exclusively by males, is pervasive in all forms of aggressive male-male interactions and that rates of body slap displays in non-contact interactions are greater than rates during fights. Preliminary examination found no relationship between dominance and rate of display, but results demonstrated that median rates of display were greater for subsequent winners, winners initiated display bouts more than losers, and that the body slap shared a positive relationship with the aggressive approach behaviour. These findings suggest that the body slap is not a submissive display, and that it likely carries information regarding resource holding potential to be used in pre-fight assessment.