Wily wasps dump foraging ants far from food sources

March 31st, 2011 - 12:56 pm ICT by IANS  

Sydney, March 31 (IANS) Wasps, frustrated at having to compete with foraging ants, pick them up in their mandibles and dump them far from food sources.

As the number of ants on the food increases, so does the frequency of ant-dropping and the distance the ants are taken, according to videotapes taken at bait stations.

For the ants, say researchers Phil Lester and Julien Grangier from Victoria University, the experience is the human equivalent of being thrown up to half the length of a soccer field, the journal Biology Letters reports.

The ants are not physically hurt but appear stunned by the drop and often do not return to the bait station, according to a Victoria University statement.

The wasp, Vespula vulgaris, is on the list of the world’s 100 worst invasive species and reaches the highest known density in South Island beech forests in New Zealand. There, when competing for food, they dominate just about every animal 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,” says Lester.

“The strategy works. It’s giving the wasp access to resources it wouldn’t otherwise have,” he adds.

“To the best of our knowledge this behaviour has never been observed before. Our results suggest that these insects can assess the degree and type of competition they are facing and adapt their behaviour accordingly,” says Grangier.

He says the wasps’ ability to tune their behaviour according to the abundance and identity of competitors could help explain why they are so widespread and invasive.

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