Gone with the wind: short- and long-term responses of leaf-cutting ants to the negative effect of wind on their foraging activity

Abstract

The fitness and survival of organisms ultimately depend on their feeding. Therefore, foraging behaviors should be selected to maximize cost-benefit ratio. Wind may restrict and modify animal movements increasing the cost of foraging, especially when the animal carries resources that intercept wind. We quantified the effect of wind on the foraging of leaf-cutting ants and evaluated whether this effect varies with 1) leaf fragment traits, such as area, mass, and shape, and 2) the characteristics of the foraging trail system. We also tested whether these ants show a short-term response to wind by selecting loads with characteristics that reduce wind interception, and a long-term response, by arranging the spatial design of the trail system in a way that reduces that effect. We found that in windy conditions, the speed of loaded ants was reduced by 55%, and ants were blown off the trail 28 times more than in windless conditions. However, wind only affected ants walking along trails that were perpendicular to wind direction or parallel upwind. Wind effect increased with area, mass, and shape of loads. At the short term, ants reduced the negative effect of wind by selecting smaller, lighter, or more elongated loads. However, trails showed no particular spatial distribution in relation to wind direction. This is the first study that quantifies the negative consequences of wind on leaf-cutting ants' foraging and reports behaviors that can reduce this effect. Our work illustrates how short-term behavioral responses can mitigate the negative effect of an understudied environmental factor on ant foraging.

Shear adhesive performance of leaf‐cutting ant workers (Atta cephalotes)

“…For small, central place foragers like ants, the energy expended during travel, particularly when carrying a load, is coupled with time spent exposed to microscopic and macroscopic hazards (Lighton, Bartholomew & Feener, ; Wetterer, ; Yanoviak et al., ). Specifically, the probability that worker ants will encounter predators, competitors, and environmental hazards (e.g., elevated temperature, wind, and rain) increases as time spent foraging away from the nest increases (Alma, Farji‐Brener & Elizalde, ; Cerda, Arnan & Retana, ; Farji‐Brener et al., ; Feener, ; Powell & Clark, ; Ribas & Schoereder, ; Spicer et al., ; Yanoviak et al., ). This is particularly true in the tropics, where environmental hazards can be extreme.…”

Foraging activity of leaf‐cutter ants is affected by barometric pressure

“…Workers of Acromyrmex lobicornis Emery in Patagonia, for instance, are affected by the wind, leading them to select smaller and lighter loads and to reduce their walking speed when carrying a leaf fragment along the trail (Alma, Farji‐Brener, & Elizalde, ). They also rely on recruiting larger foragers (Alma, Farji‐Brener, & Elizalde, ). These changes offset the effect of the wind on their foraging.…”

Wind matters: Asymmetric distribution of aphids on host plants can be explained by stems functioning as windbreaks

“…First, in the study area wind is a key factor due to its strength, high frequency and unidirectionality (Appendix ) and it strongly affects local species (Lambertucci & Ruggiero ; Shepard & Lambertucci ; Alma et al . ). Second, green and black aphids are prone to suffer wind effect because their host plant grows in open and windy areas (Patagonian steppe) and these aphids forage on naked stems elevated from the rest of the vegetation.…”