This summary was contributed by Allie Miller.
“When carrying resources from a collecting point to the nest, one would assume that animals would attempt to carry as much as possible to maximize their foraging efforts. However, among social insects that is not always the best strategy. Foragers carrying large loads might overwhelm the individuals processing the resources in the nest, causing a bottleneck. Additionally, a heavy load slows the carrier down. That may not be a significant cost for a solitary forager, but it may reduce the gains for a colony as a whole. Carrying loads well below maximum carrying performance actually reduces the burden on the resource processors and speeds up the forager, allowing for more foraging trips per unit time. But there is yet another factor whereby lighter loads can increase colony efficiency. Walking foragers, such as ants, often forage along well-defined trails and, depending on the number of foragers, this can potentially cause traffic problems. In that context, when one ant is slowed down by a heavy load it also slows down those ants following behind, regardless of load size. This phenomenon, called the ‘truckdriver’ effect – where a heavily laden truck slows down normally faster cars – describes another situation where carrying too much negatively impacts whole colony foraging efficiency.” (Klok 2011:vi)
“At low traffic flow ants can cut and carry larger leaf fragments without the concern of slowing other ants, but when traffic flow increases they refrain from cutting larger fragments. It appears that individual ant foragers leaving the nest can estimate the outbound traffic flow and use this information to estimate the future flow of returning laden ants, thereby modulating the sizes of leaf cuttings made in order to avoid delays in overall colony foraging rates. This study shows remarkable flexibility in foraging behaviour and supports the idea that leaf-cutting ants make choices not only as individuals but also collectively.” (Klok 2011:vi)