Physiological stress response to urbanisation differs between native and invasive squirrel species

Area of Science:

• Ecology
• Wildlife Biology
• Conservation Science

Background:

• Urbanization introduces novel environmental pressures impacting native wildlife and habitats.
• Species' phenotypic traits, including physiological stress responses to anthropogenic factors, may shift under these pressures.
• Invasive species may possess preadaptations for urban environments, leading to different stress responses compared to native species.

Purpose of the Study:

• To investigate differential physiological stress responses between native Eurasian red squirrels and invasive Eastern grey squirrels along a rural-urban gradient.
• To assess the influence of urbanization and intraspecific competition on the hypothalamic-pituitary-adrenal (HPA) axis activity in both species.
• To determine if invasive species are preadapted to urban stressors, potentially aiding their ecological success.

Main Methods:

• A parallel pseudo-experimental study system was employed to compare native red and invasive grey squirrels.
• Faecal glucocorticoid metabolite (FGM) concentrations were measured as an indicator of HPA axis activity.
• Measurements were taken across a rural-urban gradient and in relation to conspecific density for both species.

Main Results:

• Native red squirrels exhibited varying associations between FGMs and conspecific density across rural and suburban sites, suggesting differential HPA axis responses.
• Invasive grey squirrels showed no significant variation in FGMs concerning conspecific density or along the rural-urban gradient.
• The two species displayed distinct physiological responses to the combined effects of urbanization and intraspecific competition.

Conclusions:

• Invasive grey squirrels appear preadapted to cope with urban stressors, unlike native red squirrels.
• This preadaptation may contribute to the invasive species' successful establishment and spread in urbanized habitats.
• Understanding these differential physiological responses is crucial for developing effective conservation strategies in human-altered environments.