Older, but not wiser: social wasp colony defensive behavior decreases with time, not experience.

Behavioral shifts in animals are often driven by ontogenetic processes such as aging or life experiences, through changes in their physiology and/or gene expression. Colonies of eusocial animals such as social hymenopterans may experience behavioral shifts at the colony-level due to maturation and/or experience throughout the colony cycle. In this study, we investigated the nest defense behavior of social wasp Vespula vulgaris colonies and whether behavioral changes over time or differences in experience with simulated threats can affect aggressive response. Colonies were divided into two treatment groups and experimentally disturbed over a seven-week period by simulating a mammal attack. This procedure was carried out for "hi-freq" colonies on a weekly basis (weeks 1–6), whereas "lo-freq" groups were disturbed once every three weeks (weeks 1, 3, and 7). We show that nest defense behavior in V. vulgaris decreases over time, towards the end of the colony cycle, regardless of how frequently they faced a simulated predator attack. We found no evidence that undisturbed foraging activity or nest size could be used to predict defensive behavior. Our results show anti-predator colony behaviors in Vespula are influenced by the colony cycle, possibly through demographic shifts over time: colonies near their decline are less likely to respond to a simulated threat when compared to earlier in the season. We propose colony behavior is strongly engrained in seasonality and internal development, to a degree that it might overrule the effect of interactions with potential predators. [ABSTRACT FROM AUTHOR]