A new research has shown that in some cases, the colonies of army ants can be cooperative instead of combative, by joining neighboring colonies after the death of their respective queen.
Colonies of army ants, whose long columns and marauding habits are the stuff of natural-history legend, are usually antagonistic to each other, attacking soldiers from rival colonies in border disputes that keep the colonies separate.
Now, new work by a researcher at the Harvard Museum of Comparative Zoology and colleagues at the University of Copenhagen shows that in some cases, the colonies can be cooperative instead of combative.
In those cases, when an army ant colony loses its queen, its workers are absorbed, not killed, by neighboring colonies, and within days are treated as part of the family.
The research was conducted in an ant-rich area on the slopes of Mount Kenya.
Army ant colonies are dominated by a single, large queen who produces the eggs that give rise to all of the colony's individuals, which can number millions of workers.
When she dies, colonies quickly disappear, raising the question of what happens to the many individuals.
The work was conducted by Daniel Kronauer, a junior fellow in Harvard's Society of Fellows, over two field seasons in Kenya.
Kronauer and his colleagues followed the fates of 10 army ant colonies whose queens they had removed.
The researchers lost track of two of the colonies but observed two distinct strategies used by the remaining eight.
Most of the queenless colonies, seven out of 10, simply joined a neighboring colony - determined by genetic analysis - with the new workers slowly losing their distinct colony odor, and within days becoming fully integrated.
Since workers are normally kept from reproducing, Kronauer and his co-authors found that there doesn't seem to be a direct fitness benefit.
Instead, the authors suggested that the fusing colonies are driven by indirect fitness benefits gained because of distant relationships between colonies, and they called for more fieldwork to explore the issue further. (ANI)
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