The role of physiological constraint in the acquisition of foraging ability: development of diving capacity and behavior in young harp and hooded seals
A Collaboration with Dr. Mike Hammill, Department of Fisheries and Oceans, Canada
Graduate Students Involved: Keri Lestyk, Linnea Pearson
Knowledge of the mechanisms by which neonatal mammals acquire the tools necessary to become competent predators is crucial to our understanding of how physiological processes influence behavioral strategies. While such questions can be addressed in many species, the study of how pinniped neonates become marine predators offers several unique and significant advantages. All pinniped neonates are essentially terrestrial at birth, yet most true seals (the phocids) are foraging independently by the time they are six months of age. Therefore, pinniped neonates, unlike most terrestrial mammals, must quickly develop the physiological and behavioral skills to become efficient predators in an ecosystem where oxygen is spatially and temporally separate from their food resources. Previous research reveals that this transition is accompanied by dramatic changes in the size of body oxygen stores and the ability to regulate metabolic and heart rate patterns. It is also clear that the rate at which these changes occur varies among species with different developmental strategies.
Hooded seals are one of the most precocial mammals. They have the shorted nursing period of all the pinnipeds (4 days) and one of the earliest onsets of independent foraging (~4 weeks). In addition, pups are born with adult pelage and larger subcutaneous fat stores than most other phocid neonates. In combination, these findings suggest that hooded seal pups may show a more rapid maturation of the physiological processes related to diving than do pups of species with longer dependent periods. Early development of body oxygen reserves and metabolic control may be especially critical for young hooded seals because of their foraging ecology. Hooded seal adults make foraging dives that are remarkably long and deep for their body size, and apparently rely upon large body oxygen reserves and lowered diving metabolic rates to do so. Most juveniles studied so far attempt to mimic adult foraging patterns as soon as possible, and it is likely that young hooded seals will do so as well. However, because of their smaller size, it is unlikely that juveniles can forage efficiently at these depths. In comparison, harp seal pups are much more altricial at birth, have a longer developmental period, and once adult do not make as long or as deep dives. Therefore the rate and extent of physiological and behavioral development may differ in these two species.
Research into the physiological development of these two species has focused on measuring the oxygen stores in the blood, muscle, and lungs of pups, juveniles and adults. We are also examining the role of micronutrients in physiological development, as well as the structural and biochemical properties of the major locomotory muscles. All these studies are focused on understanding if, and to what extent the diving and foraging behavior of weaned pups may constrained by their physiological capacity. In combination with studies of the thermoregulatory abilities of young pups, we hope to assess how changes in environmental conditions may influence pup survival and population health.
Research Products to date