Biological differences between island and mainland conspecifics have been well studied, but few studies have addressed differences in stress physiology. Stressors, such as predation and competition for resources, cause the release of glucocorticoids (GCs). Characteristics of island wildlife, called "island syndrome", are attributed to low levels of predators and competitors. I tested the hypothesis that island syndrome includes differences in GC levels between island and mainland rodents using two approaches; first, using white-footed mice (Peromyscus leucopus) from a near-shore archipelago (Thousand Islands, Ontario) and the nearby mainland; second, using study-skins of deer mice (Peromyscus maniculatus) from two archipelagos offshore of Vancouver Island, British Columbia. White-footed mice in the near-shore archipelago did not show characteristics of island syndrome, or changes in GC levels (feces and hair); however deer mice from both archipelagos in British Columbia were heavier and had lower hair GCs for their size than Vancouver Island mice.
Author Keywords: Glucocorticoids, Island rule, Island syndrome, Peromyscus, Stress physiology