A Review of Ecological Factors Affecting the Annual Cycle 10 Island Populations of Seals

Abstract

Colonization of island habitats by pinnipeds for all or part of their life cycle may expose the populations to various pressures. While the advantages of an island rookery must override the disadvantages for such a situation to be selected, its most efficient utilization by one or more species can be achieved only by coordination of the annual cycles within and between species. Certain age categories or species must make way for others at critical phases of the annual cycle if habitat preferences are the same. However, more than one age group or species can coexist when habitat requirements do not overlap. Interspecific strife is reduced to a minimum by either spatial, temporal, or behavioral separation, but deleterious interspecific contact may occur. Intraspecific strife between different age classes is prevented by variable annual cycles with respect to age, but within any narrow age category such interaction as occurs may affect the number of females being fertilized and thereby act as a regulator of population size.