Grey seal maternal attendance patterns are affected by water availability on North Rona, Scotland

Abstract

Previous studies on grey seals (Halichoerus grypus) have shown that pools of water influence female distribution within inland breeding colonies. This study reveals that the availability of pools also affects maternal attendance patterns and may have implications for breeding success. An atypical dry period at the start of the 1998 breeding season on North Rona, Scotland, followed by a normal wet period, provided a natural experiment that allowed us to examine female behaviour in relation to the availability of pools. During the dry period, lactating grey seals (i) travelled long distances to gain access to water; (ii) had significantly greater rates of locomotion towards water and resulting from interactions between conspecifics; and (iii) spent significantly less time close to their pups. Long-distance locomotion and a reduction in time spent with the pup often lead to permanent mother-pup separation, resulting in starvation of the pup. However, the immediate need to gain access to water for thermoregulation or maintenance of a positive water balance outweighed the potential costs of reproductive failure, emphasising the importance of water for lactating grey seals even during the relatively cold and damp breeding season in the U.K.