Ants that build wind turrets

Ants have been on the earth for perhaps 100 million years. Ant mounts are usually 6-8m in diameter, almost 1m high and weigh approximately 40 tonnes. This is truly an engineering marvel from these tiny animals. Here comes a piece of new research that is even more fascinating

Scientists have just discovered how the grass cutting ants Atta vollenweideri build nests that stay at the right temperature. This is achieved by building porous turrets. Their vast underground lairs may contain up to seven million insects that tend the fungal garden that feeds their young. The control of temperature is absolutely essential for the fungus to grow properly.

The researchers closely examined the question whether turrets are simply heaps of disposed soil, or result from the import and a particular spatial arrangement of materials. The scientists daily offered different building materials, i.e., clay, coarse and fine sands, which workers collected and deposited around a nest opening to construct a turret.  The researchers regularly changed the amount of each material that was available to them. Workers did not select particular materials to be imported for turret building, but were selective in their spatial distribution and assembly into the turret structure. Simulated rain damage to the nest was done by pouring water on to the structure. The ants aimed at the maintenance of a porous yet mechanically-stable structure

The ants invariably made turret walls that were highly porous and allowed air to flow through. The ants construct the turrets by stacking sand grains and little balls of clay that they mould with their jaws. They are able to sense minute differences in the density of the soil at different depths.

The researchers say Irrespective of the materials used, walls showed a marked regular porosity in the range 50–60%, with the exception of secondary galleries that occasionally permeated the turret structure, which evinced lower porosity and therefore a more compact microstructure.

  

Journal reference

The Construction of Turrets for Nest Ventilation in the Grass-Cutting Ant Atta vollenweideri: Import and Assembly of Building Materials 
Marcela I. Cosarinsky and Flavio Roces

Journal of Insect Behavior

DOI: 10.1007/s10905-011-9290-8 Online