A conceptual model of the variation in parental attendance in response to environmental fluctuation: foraging energetics of lactating sea lions and fur seals

1. A conceptual model is described and tested using empirical data that predicts how air-breathing marine vertebrates that are tied to shore for reproduction, but feed at sea, should respond to changes in prey availability. 2. The model examines the trade-off between changes in trip duration and foraging intensity as measured by field metabolic rate. It predicts that parents should increase the intensity of effort, and hence metabolic rate, prior to increasing the duration of foraging trips to maintain nutrient delivery to the young. 3. The model was tested with data on the foraging energetics and trip duration of four species, northern and Antarctic fur seals and California and Australian sea lions, each studied over two contrasting seasons. 4. The response of these marine predators to changes in prey availability due to climate driven environmental perturbation was found to support the conceptual model. Copyright (c) 2008 John Wiley & Sons, Ltd.