Abstract
The extent to which animals respond fearfully to novel stimuli may critically influence their ability to survive alongside humans. However, it is unclear whether the fear of novel objects, object neophobia, consistently varies in response to human disturbance. Where variation has been documented, it is unclear whether this variation is due to a change in fear towards specific novel stimuli, or whether it is symptomatic of a general change in fear behaviour. We measured levels of object neophobia in free-flying birds across urban and rural habitats, comparing corvids, a family known for being behaviourally flexible and innovative, with other urban-adapting bird species. Neophobic responses were measured in the presence of different types of objects that varied in their novelty, and were compared to behaviour during a baited control. Corvids were more neophobic than noncorvid species towards all object types, but their hesitancy abated after conspecifics approached in experimental conditions in which objects resembled items they may have experienced previously. Both sets of species were faster to approach objects made from human litter in urban than rural areas, potentially reflecting a category-specific reduction in fear based on experience. These results highlight species similarities in behavioural responses to human-dominated environments despite large differences in baseline neophobia.
Highlights
The extent to which animals respond fearfully to novel stimuli may critically influence their ability to survive alongside humans
Since human litter provides opportunities for foraging that requires the manipulation of novel objects, such as food packaging, reduced neophobia may make animals more likely to innovate with novel food or objects when invading novel habitats (Greenberg, 2003; Greenberg & Mettke-Hofmann, 2001; Martin & Fitzgerald, 2005)
To determine the factors influencing whether or not birds appeared at tables, we ran a generalized linear mixed model (GLMM) with a binomial error structure (Appeared 1⁄4 1, Did not appear 1⁄4 0)
Summary
The extent to which animals respond fearfully to novel stimuli may critically influence their ability to survive alongside humans. Some urban birds are able to avoid investing in unnecessary antipredator responses by selectively responding to specific threatening humans (Davidson, Clayton, & Thornton, 2015; Lee, Lee, Choe, & Jablonski, 2011; Levey et al, 2009) It is unclear whether areas of human disturbance favour selective reductions in fear towards other stimuli, such as potentially dangerous objects. Urban common mynas, Acridotheres tristis, have been shown to be less neophobic than suburban conspecifics (Sol, Griffin, Bartomeus, & Boyce, 2011), and urban groups of house sparrows, Passer domesticus, solve tasks more quickly than rural ones (Liker & Bokony, 2009) Such reductions towards fear-related stimuli in urban environments has been documented in other behaviours such as flight initiation distance (Clucas & Marzluff, 2012; Mccleery, 2009; Moller, 2010; Møller, 2008), a dampened corticosterone stress response (Grunst, Rotenberry, & Grunst, 2014) or both (Atwell et al, 2012) (but note that these stress hormone patterns are not universal, see Bonier, 2012). Elevated levels of object avoidance have been documented in house sparrows and shiny cowbirds, Molothrus bonariensis, in urban compared to rural habitats (Echeverría & Vassallo, 2008)
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