Defensive Moves

Ants come in variety of shapes and sizes and live in large communities in which the various members cooperate to make the colony thrive. Colonies have different specialties, such as cutting leaves for fungal farms or the free range farming of aphids for honeydew. Ant colonies appreciate how well off they are, and will defend their patch vigorously if they can. Some species have nastier habits than others. For example, Protomagnathus americanus makes slave raids on adjacent colonies of other species to carry off brood. They don’t succeed without a fight of course, and the host colony can lose many workers and their queen while trying to defend their young.

Being raided and finding your young carried off is not something that a colony is willing to put up with, and a new study (1), by Pamminger et al from U of Munich, has shown how host colonies of Temnothorax curvipinosus mobilized their militias to seek and destroy any slavemaker spies who had infiltrated to assess the cost/benefit of a raid on their colony. The experiments were carried out under laboratory conditions to eliminate extraneous factors such as the seasons and competing colony crowding.

 A dead spy or two left lying about for a few minutes was enough to set off the chemical alarms and the militias cracked down. Non-nestmates who were not from the slavemakers were not treated so harshly, maybe roughed up a bit on occasion, though. No slavemaker scout was shown any mercy.

Mobilization took up to 5 minutes, and would last at peak for about 3 or 4 days, with a wind down over the next two weeks. The wind down occurred even though it was still raiding season, indicating that the their defense budget considerations came into play. Mobilization of militias is associated with costs. Such as lowering community foraging efficiency and the increased stress levels reducing longevity and brood production. And a well-run ant community has to work out a balanced budget based on resources and risk.


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