The effect of social context on measures of boldness: Zebra finches (Taeniopygia guttata) are bolder when housed individually.

Boldness can be quantified as latency to access resources in novel contexts. Although social interactions influence boldness, especially in species such as zebra finches (Taeniopygia guttata) that are sociable and live in groups, the boldness of individuals is generally characterized in isolation. The objective of this study was to examine how proximity of and familiarity with flock members influenced boldness, which is often assumed to be stable across contexts. We measured boldness as the latency of adult zebra finches to forage when a novel object was within a food dish in five social contexts: (1) social isolation, (2) adjacent to novel flock, (3) adjacent to familiar flock, (4) within novel flock, (5) within familiar flock. Our measure of boldness showed individual consistency across social contexts. However, when mean response values across different social contexts were compared, individuals were bolder (i.e. had lower latencies) when housed and tested individually, regardless of the presence or absence of a flock nearby. We found no evidence of sex, dominance rank, or flock members' boldness on the boldness of a focal bird. Our study deepens understanding of the influence of the social environment on boldness in zebra finches by demonstrating an influence of physical proximity. We encourage continued work examining boldness in different social contexts in zebra finches, as rigorous work in one system may help us understand the factors that influence the relative stability or flexibility of this trait.