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It’s raining ants

30 March 2011

New research published in Royal Society journal Biology Letters has identified a surprising and previously unknown animal behaviour, showing that wasps frustrated by having to compete with ants pick them up in their mandibles, fly off and drop them away from the food.  As the number of ants on the food increases, so does the frequency of ant-dropping and the distance the ants are taken.

Researchers Dr Phil Lester and Dr Julien Grangier at Victoria University say that for the ants the experience is the human equivalent of being thrown up to half the length of a football field. The ants are not physically hurt but appear stunned by the drop and often do not return to the bait.

Wasp removing ants from bait station (9 secs).

The wasp, Vespula vulgaris, is on the list of the world’s 100 worst invasive species and is endemic in New Zealand’s South Island beech forests. In terms of food competition, they dominate just about every animal in this location, except native ants.

“Despite being 200 times smaller, the ants are able to hold their own by rushing at the wasps, spraying them with acid and biting them.  Eventually the wasps get so angry they pick up the ant, take it away and return to eat the food.  The strategy works. It’s giving the wasp access to resources it wouldn’t otherwise have,” said Dr Lester.