Abstract
Island rodents are often larger and live at higher population densities than their mainland counterparts, characteristics that have been referred to as “island syndrome”. Island syndrome has been well studied, but few studies have tested for island-mainland differences in stress physiology. We evaluated island syndrome within the context of stress physiology of white-footed mice (Peromyscus leucopus) captured from 11 islands and five mainland sites in Thousand Islands National Park, Ontario, Canada. Stress physiology was evaluated by quantifying corticosterone (a stress biomarker), the primary glucocorticoid in mice, from hair and its related metabolites from fecal samples. White-footed mice captured in this near-shore archipelago did not display characteristics of island syndrome, nor differences in levels of hair corticosterone or fecal corticosterone metabolites compared with mainland mice. We suggest that island white-footed mice experience similar degrees of stress in the Thousand Islands compared with the mainland. Although we did not find evidence of island syndrome or differences in glucocorticoid levels, we identified relationships between internal (sex, body mass) and external (season) factors and our hormonal indices of stress in white-footed mice.
Highlights
Studying island ecosystems and species has been central to the development of ecological and evolutionary theory (Foster, 1964; MacArthur & Wilson, 1967; Van Valen, 1973; Lomolino et al, 2012; Warren et al, 2015)
We focused on white-footed mice (Peromyscus leucopus) because they are the most abundant small mammal in Thousand Islands National Park (Werden et al, 2014), and Peromyscus has been the focus of many studies that provide the basis for island syndrome (Adler & Levins, 1994)
More traps were tripped at island sites than mainland sites (23% ± 12.8%), and it was likely that trap disturbance contributed to the high degree of variation in trapping success across habitat types
Summary
Studying island ecosystems and species has been central to the development of ecological and evolutionary theory (Foster, 1964; MacArthur & Wilson, 1967; Van Valen, 1973; Lomolino et al, 2012; Warren et al, 2015). In response to decreased predator pressure and interspecific competition, combined with changes in food availability on islands, small mammals evolve towards gigantism upon arrival to islands while larger species often display dwarfing (Lomolino et al, 2012). This pattern, observed across numerous archipelagos, contributes to the evolutionary trend called the ‘‘island rule’’ (Van Valen, 1973). Behavioural and morphological changes co-occur in small mammals following island.
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