Lost ants search cleverly
By adapting their search, ants can get
back to the nest as fast as possible,
avoiding heat and predators.
Image: iStockphoto

A lost desert ant will use the distance of its foraging excursion to work out a sophisticated search pattern to get home safely, according to new research from the Australian National University.

The analysis, conducted by Dr Tobias Merkle of the ANU Research School of Biology and Rüdiger Wehner of the University of Zürich, Switzerland, shows that desert ants are highly adaptable in finding their nests. If no visual landmarks are available to guide them home, the ants use the maximum distance of their outbound journey to calibrate search circles.

Dr Merkle said that the adaptive search techniques used by the ants enable them to find their nests as quickly as possible, making them less of a target for potential predators and far less vulnerable to heat.

“The maximum distance they have ventured out is used for the calibration of their search patterns,” said Dr Merkle. “That is, the larger the distance has been, the wider the search loops. They remember this distance as they remember where they have found food and – if this has been a rewarding food site – return to that place during their next foraging excursion.”

He added that the ants use a technique called path integration to get them close to their nest, and then start their systematic search for the nest. “Our research shows that – if they have ventured out far from the nest - they use larger loops from the beginning rather than search one small area with high intensity. The latter they do after very short foraging excursions when they are sure that they are close to the nest entrance,” Dr Merkle said.

While a similar behaviour has been documented in desert isopods and cockroaches, this study of desert ants, finally identifies the key factor that calibrates the search patterns. The research paper, ‘Desert ants use foraging distance to adapt the nest search to the uncertainty of the path integrator’, is published in the latest Behavioral Ecology.

To test the ants’ abilities to find their way back to the nest, Dr Merkle and his team drew enormous grids around the ants’ nests to map their journeys home. The work was done in North Africa in cooperation with the universities of Bonn, Germany, and Zürich, Switzerland.

“We compared ants whose foraging excursions were very different – long and tortuous, or straight and short. All groups of ants, however, had ventured out the same maximum distance from the nest. All different groups of ants showed very similar search patterns. This led to our conclusion that the distance determines the extension of their searches, because that’s the only factor that was the same for all of them,” he said.

Editor's Note: Original news release can be found here.