Migration of Marine Mammals

Abstract

Marine mammals utilize marine resources throughout the world’s oceans, but the location of food is often spatially and temporally separated from environments that are required for reproduction. There is an increasing understanding of migratory behaviour because of the use of new techniques to track marine mammals. Many of the mysticete cetaceans exploit seasonally rich food supplies in the polar summer but migrate to sub-tropical waters during winter when mating and birth take place. In some cases, these migrations follow predictable routes but those cetacean species with the largest body size are, in general, those that migrate over the longest distances. The greatest understanding of migratory patterns comes from pinnipeds that are restricted to giving birth on land or ice. Again, body size appears to have co-evolved with migration behaviour. Those animals that have the largest body size also have the largest absolute energy requirements. Consequently, large marine mammals must forage in regions of relatively abundant prey in order to be able to feed profitably. Owing to differences in the allometric scaling of metabolic rate and energy stores with body mass, large body size confers greater fasting capabilities. This means that large marine mammals can migrate further in search of richer food patches. The range of body size amongst the pinnipeds and cetaceans may have evolved as a result of selection to exploit the high degree of heterogeneity of food supply in the oceans and to allow animals to exploit food remote from where they are constrained to reproduce.