The Impact of the Leaf Cutter Ant Atta Colombica on the Energy Flow of a Tropical West Forest
1973
Lugo, Ariel E. | Farnworth, Edward G. | Pool, Douglas | Jerez, Patricio | Kaufman, Glen
The patterns, quantity, and activities associated with the leaf—cutting of Atta colombica were studied August 20—27, 1971, in a lowland tropical wet forest at Osa Peninsula, Costa Rica (Lat. 08 42'N Long. 83 29'W). The study nest had an area of 44.8 m² and covered 1.4 ha of forest floor. Daily, on a m² of forest floor, the study nest had inputs of 10.17 leaf fragments with an area of 0.0108 m², a weight of 0.0813 g, an ash content of 0.0039 g, and a potential energy of 0.3455 Kcalories. The ants return to the forest floor 0.0525 g of refuse with a potential energy of 0.0764 Kcalories and an ash content of 0.0212 g/m² day. It was calculated that the leaf—cutting activity of ants reduced the gross production of the forest by 1.76 Kcal/m² day but accelerated net production by at least 1.80 Kcal/m² day through the return of ash rich in phosphorus to the forest floor. The size of the Atta nest may be determined by the balance of the energy input to the nest and the cost of obtaining, carrying (concentrating), and distributing the potential energy into the nest. Of a work force of 12,000 ants/m² of trail, 75% were not carrying leaves and were assumed to be doing trail maintenance work. Rainfall and litter fall were the main obstacles of leaf transport, which was about 70% efficient. The ant's energy allocation for maintenance, which limits growth, and the establishment of reward feedbacks to their energy producers have implications for man's urban system development.
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