Seasonally breeding predators, which are limited in the. time available for provisioning young at a central location, and by the fasting abilities of the young, are likely to maximize energy delivery to the young by maximizing the rate of energy delivery averaged over the whole period of investment. Reduction in food availability or increased foraging costs will alter the optimal behavior of individuals. This study examined the behavioral adaptations of a diving predator, the Antarctic fur seal to increased foraging costs during lactation. One group of mothers (n = 5, treatment) was fitted with additional drag to increase the cost of transport in comparison with a control group (n = 8). At the scales of the individual dives, the treatment group made more shorter, shallower (