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Differing vigilance among gray squirrels (Sciuridae carolinensis) along an urban–rural gradient on Long Island

Sarno, Ronald J., Parsons, Michael, Ferris, Angela
Urban ecosystems 2015 v.18 no.2 pp. 517-523
Sciurus carolinensis, aggression, behavior change, ecosystems, habitats, human population, humans, landscapes, parks, population density, squirrels, traffic, urban areas, urbanization, wildlife
Urbanization has had far-reaching effects on the wildlife that have adapted to this novel landscape. Not only have wildlife endured shifts in ecosystem function as a result of urbanization, but in many areas there has been a fundamental behavioral change. This “urban wildlife syndrome” – the collection of observable traits of wildlife species undergoing urbanization – prompted us to examine the effect of urbanization on vigilance of eastern gray squirrels (Sciurus carolinensis). We hypothesized that squirrels in more urban locations, due to presumed higher squirrel density and familiarization with humans, would be less vigilant than squirrels in more rural sites. We assigned study sites (i.e. city parks) to one of four rank categories of urbanization based upon human population density. In contrast to our original hypothesis, squirrels in urban sites were more vigilant than squirrels in less urban areas. In fact this difference was punctuated by an approximate 42 % reduction between moderately urban and semi-rural habitats. Squirrel density had a positive, yet weak, effect on vigilance time. Elevated intraspecific aggression, unpredictable changes in vehicular and pedestrian traffic, and associated noise levels and disturbance in urban settings where squirrels occur, may be responsible for more variable and heightened states of vigilance in the urban setting.