FARJI-BRENER Alejandro Gustavo
congresos y reuniones científicas
Collective response of leaf-cutting ants to the negative of wind on their foraging activity
Congreso; XXII Simposio de mirmecología-International Ant Meeting.; 2015
Organisms have to deal with surrounding environment in order to survive and reproduce; one advantage of social animals is that can use both individual and collective strategies to achieve this. In regions like Patagonia, where wind is constant and intense, foraging rate of leaf-cutting ants is reduced by wind effect on workers? speed and movement. Leaf-cutting ants have the particularity that whole body adhesion and contact area per leg increase with body size; therefore, they might solve the wind effect collectively increasing the foragers? size in windy conditions. Our aims were to test whether (1) the wind effect on ants? speed and movement decrease with increase of ant size; and (2) leaf-cutting ants are able to solve the wind effect increasing the foragers? size. To evaluate this, we worked with Acromyrmex lobicornis, a leaf-cutting ant that inhabits in Patagonia. On the one hand, to test the wind effect on large and small ants, we generated artificial wind (4 km/h) with computer coolers in the trails of 11 nests, and measured for large and small ants (5-7 and 2-4 mm, respectively) the speed without wind minus speed with wind, number of times ants were blown away the trail by wind effect, and time spent by ants for accustoming themselves to a wind condition (hereafter transition time). On the other hand, to test whether ants reduce the wind effect increasing the foragers? size, we measured the load ants? size in 10 nests during 2 min 30 s in natural windy (4-9 km/h) and windless conditions (0 km/h). We found that the wind effect was lower on large ants than on small ones; the speed difference, number of times ants were blown away the trail, and transition time were lower for large ants. According to that, we found that in windy conditions the load ants? size was greater than in windless conditions (mean ± SE: 5.2 ± 0.06 and 4.2 ± 0.07 mm, respectively). Our results suggest that leaf-cutting ants reduce the negative wind effect through an increase in the foragers? size. Moreover, these results highlight the ant plasticity and the ability of a social organism to deal with an environmental factor as a group taking advantage of individual diversity