Ants are famously collaborative. But they are also fiercely competitive. Workers from the same colony sacrifice their own reproductive opportunities to boost that of a single queen or, occasionally, a small ruling council. But they defend the patch on which their nest sits vigorously―often to the death. Unless, that is, they are Argentine ants in Europe. It has been known for some time that this species, although normally aggressive in its native habitat, has relaxed into placid mutual toleration in the laid-back environment of the Mediterranean. But until Ta-tiana Giraud, of the University of Lausanne, and her colleagues started probing, it was not realised just how far this toleration extended. Dr Giraud, whose work has just been published in the Proceedings of the National Academy of Science, collected workers from 33 Argentine-ant nests scattered along the Mediterranean coasts of Italy, France and Spain, and the Atlantic coasts of Spain and Portugal. Measured along the coastline, the extremities of this distribution are 6,000km apart.
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