SEX-DIFFERENCES IN THE NURSING RELATIONSHIP BETWEEN MOTHERS AND PUPS IN THE ATLANTIC HARBOR SEAL, PHOCA-VITULINA-CONCOLOR

Sex differences in the dynamics of the relationship between harbour se al mothers and their pups were investigated. An index of pair proximit y governance suggested that pups became increasingly responsible for m aintaining the distance between the pair over the course of the nursin g period. Male pups demonstrated a stronger tendency to control intrap air distance than female pups. A Nursing Index utilizing suckling bout initiations and terminations revealed that, as weaning approached, pu ps became progressively more responsible for the continuance of nursin g. Male pups exhibited more control than female pups, primarily throug h initiating a greater portion of the bouts. On-teat times averaged 4. 08 min per bout, with no significant differences between male and fema le pups. Male pups, however, nursed a greater portion of haul-out time due to higher bout frequencies obtained through more bout initiations . Mothers did not preferentially reject attempts to nurse by pups of e ither sex. These results suggest that the tenet of parental investment theory suggesting male pups enjoy preferential investment may be misl eading. In harbour seals, male pups seem actively to seek out resource s, as opposed to any inherent strategy on the part of the mother.