Serum biochemistry suggests grey squirrels (Sciurus carolinensis) have poorer physiological condition in urban settings

Human food waste in cities presents urban wildlife with predictable, easily accessible high-calorie food sources, but this can be both beneficial and harmful for individual health. We analyzed body condition and serum chemistry (electrolyte levels, markers of kidney and liver function, protein, glucose, and cholesterol) in an urban and rural population of eastern grey squirrels ( Sciurus carolinensis ) to assess whether proximity to the human food waste that is associated with urban habitats had ill effects on health. We found no differences in body condition between habitats and no evidence of malnutrition at either site. However, urban squirrels had higher blood glucose, lower potassium, phosphorus, chloride, and albumin:globulin ratios. These results align with previous findings of increased dietary sugar in cities, and suggest that urban populations of grey squirrels are under greater environmental stress than rural populations.