Contrasting responses of bumble bees to feeding conspecifics on their familiar and unfamiliar flowers

Abstract

Animals exploiting their familiar food items often avoid spatio-temporal aggregation with others by avoiding scents, less rewarding areas or visual contacts, thereby minimizing competition or interference when resources are replenished slowly in patches. When animals are searching or assessing available food sources, however, they may benefit from reducing sampling costs by following others at food sites. Therefore, animals may adjust their responses to others depending on their familiarity with foraging situations. Here, we conducted field experiments to test whether nectar-collecting bumble bees make this adjustment. We allowed free-foraging bees to choose between two inflorescences, one occupied by a conspecific bee and another unoccupied. When bees were presented with flowers of a familiar type, they avoided occupied inflorescences. In contrast, bees visited an occupied inflorescence when the flower type was unfamiliar. To our knowledge, this is the first report suggesting that animals adjust their responses to feeding conspecifics depending on their familiarity with food sources. Such behavioural flexibilities should allow foragers to both explore and exploit their environments efficiently.

Visual attention in a complex search task differs between honeybees and bumblebees

“…In such habitats, resources are sparsely and evenly spread (Dornhaus and Chittka, 2004a) and insects visiting flowers must put significant effort in individual flower detection and identification. Bumblebees are solitary foragers, and their decisions depend basically on their own experience or public information (Kawaguchi et al, 2007;Leadbeater and Chittka, 2007). They keep their personal foraging rate high by regularly probing unfamiliar flowers (Heinrich, 1979) and abandoning food sources shortly after the first signs of a possible nectar depletion (Townsend-Mehler et al, 2011).…”

Adaptive foraging behaviour of individual pollinators and the coexistence of co-flowering plants

“…Pollinators tend to adopt more profitable strategies by individual or social learning [14,24]. For example, learning dynamics of a strategy can be governed by a replicator equation:…”

“…However, it is clearly not the direct cause for pollinators to adopt the foraging strategy; as Charles Darwin remarked, 'That insects should visit the flowers of the same species for as long as they can is of great significance to the plant, as it favours cross fertilization of distinct individuals of the same species; but no one will suppose that insects act in this manner for the good of the plant [13, p. 419]'. For most pollinators, flower constancy is not a fixed trait but a plastic foraging strategy [14]. In general, there is a trade-off in foraging efficiency between maintaining flower constancy and frequently switching plant species.…”

Social Information Use in Foraging Insects

“…One explanation might be that individuals join each other as an aggressive response, or because they are simply attracted to conspecifics; indeed, bumble bees also tend to land beside conspecifics in a nonforaging context (Leadbeater and Chittka 2007b). Interestingly, however, a number of studies have found that joining behavior often occurs only when foragers visit flower species that they are not familiar with (Slaa et al 2003;Leadbeater and Chittka 2005;Kawaguchi et al 2007). Thus, perhaps joining behavior has adaptive benefits for foraging efficiency, not because it leads to individual rewarding flowers, but because it encourages sampling of rewarding flower species that might otherwise be ignored.…”

“…If individual nectaries are rapidly drained by the foragers that find them, joining conspecifics will be a poor option unless the inflorescences in question contain an unusually large number of flowers. Nonetheless, an attraction to occupied inflorescences has been found in many pollinators, including bumble bees, stingless bees, honey bees, and wasps (Brian 1957;Wenner and Wells 1990;Slaa et al 2003;Leadbeater and Chittka 2005;Kawaguchi et al 2007). Why should an apparently maladaptive behavior be so common?…”