Exploration and Aggregation of Differently Sized Camponotus japonicus Worker Ants

Ants, as eusocial insects, rely on the division of labor shaped by factors such as age and body size, facilitating colony-level behavioral flexibility under novel conditions. In this study, we examined how body size is related to exploratory and aggregation behaviors, along with the role of inactivity, in foragers of the polymorphic ant Camponotus japonicus exposed to a novel environment. Minor, media, and major workers were tested separately in a round arena, with behaviors filmed for an hour. While exploratory activity declined with time, it did not differ significantly among size classes. In contrast, aggregation behavior was size-dependent: larger workers aggregated more and formed bigger clusters than smaller workers, and aggregation generally increased in later acclimation phases. However, the timing of aggregation did not vary across size classes. The proportion of time inactive and the spatial distribution of inactive ants remained consistent across size classes, though overall inactivity increased over time. Furthermore, the presence of inactive ants within clusters consistently reduced the movement speed of other ants within the cluster, irrespective of their size classes. These findings suggest that behavioral variations in C. japonicus may reflect functional specialization across worker sizes, promoting collective resilience when colonies encounter unfamiliar environments.