Print PageHarvester ants are common in Americas, but have their ecological aspects well studied only in North America. The harvester ant Pogonomyrmex naegelii was studied in cerrado savanna in Uberlândia, central Brazil. The aims of this study were to answer how are the structure, nest composition, activity rhythms and foraging ecology of this ant species in the tropical savanna. Colonies (N=15) were observed weekly in the field (May 2008 to June 2009), totaling 68 days (177 hours; ad libitum/one observer).
Results/Conclusions
The species nests on the ground (46,67± 25,17cm in deep) and colonies have in average just over 400 workers. Nest entrances are inconspicuous (0,72 ± 0,32cm in diameter) and are often covered with dry leaves, sticks or stones. Ant activity is diurnal (9 a.m. to 4 p.m. - dry season; 11 a.m. to 6 p.m. - wet season), positively correlated with air temperature and negatively correlated with relative humidity. The activity peak, on both seasons, always occurred in the day period of highest air temperature and lowest relative humidity. Foragers leave the nest independently and individually search for food within the leaf litter or on bare ground, never climbing on plants. The foraging areas varied in size from 3.32 to 29.22 m2 (dry season) to 1.94 to 7.27 m2 (wet season). Workers collect seeds (34 plant species), flowers, fruits, vegetative plant parts, as well as scavenge dead animal matter. Seeds were significantly more frequent in the diet during the dry season while animal items were more frequent in the wet season. Results suggest that P. naegelii is an important seed consumer from cerrado plants, mainly Poaceae during the dry season. This is the first study on behavioral and foraging ecology of a Pogonomyrmex harvester ant in Brazil.
