The ‘truck‐driver’ effect in leaf‐cutting ants: how individual load influences the walking speed of nest‐mates

Abstract

The foraging behaviour of social insects is highly flexible because it depends on the interplay between individual and collective decisions. In ants that use foraging trails, high ant flow may entail traffic problems if different workers vary widely in their walking speed. Slow ants carrying extra‐large loads in the leaf‐cutting ant Atta cephalotes L. (Hymenoptera: Formicidae) are characterized as ‘highly‐laden’ ants, and their effect on delaying other laden ants is analyzed. Highly‐laden ants carry loads that are 100% larger and show a 50% greater load‐carrying capacity (i.e. load size/body size) than ‘ordinary‐laden’ ants. Field manipulations reveal that these slow ants carrying extra‐large loads can reduce the walking speed of the laden ants behind them by up to 50%. Moreover, the percentage of highly‐laden ants decreases at high ant flow. Because the delaying effect of highly‐laden ants on nest‐mates is enhanced at high traffic levels, these results suggest that load size might be adjusted to reduce the negative effect on the rate of foraging input to the colony. Several causes have been proposed to explain why leaf‐cutting ants cut and carry leaf fragments of sizes below their individual capacities. The avoidance of delay in laden nest‐mates is suggested as another novel factor related to traffic flow that also might affect load size selection The results of the presennt study illustrate how leaf‐cutting ants are able to reduce their individual carrying performance to maximize the overall colony performance.

Leaf-cutting ants as road engineers: the width of trails at branching points in Atta cephalotes

“…In this case, a trail that is too wide could lead to a lower rate of food return to the nests because of reduced ant contacts, decreasing foraging efficiency (Burd et al, 2002;Dussutour et al, 2007). However, a trail that is too narrow would have the same negative effect as a wider trail if it promotes an excessive number of collisions and traffic congestions (Burd and Aranwela, 2003;Farji-Brener et al, 2011). Here, we found an additional factor that may affect foraging efficiency and, in turn, the width of trails: the border effect.…”

Panic escape polyethism in worker and soldier Coptotermes formosanus (Isoptera: Rhinotermitidae)

“…Using ants as model organisms greatly enhanced the understanding of traffic dynamics under normal and panic conditions. These studies showed the “wisdom” of ants in avoiding clogging and jamming of the foraging trails and escape flows (Burd et al ., ; Dussutour et al ., , , ; John et al ., ; Farji‐Brener et al ., ; Soria et al ., ; Boari et al ., ). For example, Boari et al .…”

“…These studies showed the "wisdom" of ants in avoiding clogging and jamming of the foraging trails Correspondence: Gregg Henderson, Department of Entomology, Louisiana State University, Room 404, Life Sciences Building, Baton Rouge, LA 70803, USA. Tel: +1 225 578 1831; fax: +1 225 578 1643; email: grhenderson@agcenter.lsu.edu and escape flows (Burd et al, 2002;Dussutour et al, 2004Dussutour et al, , 2007Dussutour et al, , 2009John et al, 2009;Farji-Brener et al, 2011;Soria et al, 2012;Boari et al, 2013). For example, Boari et al (2013) studied the egress time of Argentine ants, Linepithema humile Mayr, from heated containers, and concluded that ant evacuation is "group-efficient" because "they do not display any impatient or selfish evacuation behavior."…”

Extended phenotypes and foraging restrictions: ant nest entrances and resource ingress in leaf‐cutting ants

“…Previous research has demonstrated that the input of food into the colony may be restricted by the design of the trail system (Bruce & Burd , Farji‐Brener et al . , ). Our results suggest that the entrance design of leaf‐cutting ant nests can also restrict the rate of food input.…”