Urban noise and its predictability moderate perceived risk associated with roads in grey squirrels

Abstract

Human activity and disturbance are thought to be perceived as a source of risk analogous to predation risk in wildlife. As such, can alter behaviour and habitat use of foraging animals. Through increased exposure to human disturbance, urban wildlife may face an increase in perceived risk during food acquisition. Urban habitats also include novel resources that could result in urban wildlife having to face distinct tradeoffs associated with foraging and patch use. To examine how a successful invasive mammal, the eastern grey squirrel, balances risk and safety under human disturbance, we measured giving-up densities (GUD) at artificial food patches placed at sites subject to varying levels of urbanisation to investigate how features associated with human disturbance might influence feeding decisions. We found differences in GUDs between ‘safe' and risky' patches were reduced closer to roads under noisy conditions, suggesting that the risk of predation is perceived by squirrels as reduced when disturbance from human activities is highest. There was also a significant effect of the variability in noise levels on patterns of patch exploitation associated with roads, with the larger GUD differences between safe and risky patches found further from roads exacerbated under more variable noise levels, suggesting the consistency of human disturbances also moderated squirrel risk perception while foraging around roads. Our results suggest that human activities can have doubled-edged impacts on the urban landscape of fear through offering reduced risk from predators whilst increasing foraging costs via noise disturbance.