Getting older, getting smarter: ontogeny of foraging behaviour in the tropical social wasp Ropalidia marginata

Abstract

Desert ants and honey bees start foraging when they are a few days old, and subsequently increase their foraging effort and the amount of foraged food. This could be an optimal strategy for scavenger/gatherer animals inhabiting landscapes with fewer features. However, animals inhabiting cluttered landscapes, especially predatory animals, may require substantial familiarity with foraging landscapes to forage efficiently. They may acquire such spatial familiarity with increasing age/experience, and eventually reduce their foraging effort without compromising on foraging success/efficiency. To check whether this holds for the individually foraging predatory tropical paper-wasp Ropalidia marginata, we recorded the number and duration of all foraging trips, the identity of foraged materials, and the directions of outbound and inbound flights (with respect to the nest) of known-age wasps for three consecutive days from three naturally occurring colonies; thus, we measured behavioural profiles of wasps of various ages, and not from the same wasp throughout its lifespan. Wasps increased their foraging duration rapidly until about 4 weeks of age, during which they rarely brought food, although some wasps brought building material and water. Thereafter, their foraging duration started decreasing. Nevertheless, their foraging success/efficiency in bringing food kept on increasing. With age, wasps developed individual directional preferences for outbound and inbound flights, indicating the development of spatial memory for rewarding sites. Also, the angular difference between their outbound and subsequent inbound flights gradually increased, indicating older wasps may have followed tortuous foraging routes. High investment in early life to acquire familiarity with foraging landscapes and using that later to perform efficient foraging could be an optimal strategy for individually foraging animals inhabiting feature-rich landscapes.

Keywords: Behavioural ecology; Evolution; Foraging strategy; Social hymenoptera; Spatial learning and memory.