Personality and plasticity in neophobia levels vary with anthropogenic disturbance but not toxic metal exposure in urban great tits: Urban disturbance, metal pollution and neophobia.

Animal personalities, as defined by repeatable among individual differences in behavior, can vary across urbanization gradients. However, how urbanization affects personalities remains incompletely understood, especially because different urban stressors could affect personality traits in opposing ways, whereas most previous studies have considered only one urban disturbance factor. For instance, novel habitat features could favor reduced neophobia, whereas exposure to pollutants could increase risk sensitivity through neurotoxic or hormonal effects. To address this contingency, we studied object neophobia in four urban populations of great tits (Parus major) that vary in exposure to metal pollution and anthropogenic disturbance, as quantified by proximity to roads and pathways. We measured the return latency of incubating females when flushed from the nest and presented with up to two different novel objects, allowing quantification of behavioral repeatability and plasticity. To separate neophobia from sensitivity to disturbance, we also conducted baseline trials, in which females were flushed but no object was presented. We additionally measured exploration behavior and aggression (hissing) during nest defense, to explore whether suites of behaviors covary with urbanization, and examined whether neophobia affects reproductive success. Sensitivity to disturbance and neophobia were repeatable, and thus represent personality traits. Moreover, females occupying territories near roads and pathways had shorter return latencies during novel object but not baseline trials, suggesting a specific reduction in neophobia in disturbed areas. Plasticity in neophobia also increased with disturbance level. In contrast, metal exposure did not affect neophobia or sensitivity to disturbance, despite negatively correlating with exploration behavior. Neophobia correlated with exploration behavior, but not aggression or reproductive success. Results suggest that shifts in personality types in urbanized areas might involve specific reductions in neophobia, rather than general reductions in sensitivity to disturbance, and unexpectedly indicate no effect of toxic metals on risk sensitivity.