European rock ants at a crossroads will most often turn left, a group trait that may boost survival, a study said Wednesday.
Many creatures, including humans, show a preference for one side over the other in movement or the senses.
Ninety percent of humans, for example, are right-handed, while the European honeybee relies predominantly on its right eye for detecting objects, said the study in the journal Biology Letters of the British Royal Society.
When it comes to behaviour, the common American cockroach has a bias for turning right in a Y-shaped tube, and giant water bugs mainly opt left in underwater T mazes.
In animals with spines, like humans, such asymmetry is thought to be linked to the different specialisation of the two lobes of the brain, and to allow them to carry out two tasks simultaneously.
A team from the universities of Bristol and Oxford decided to test whether European rock ants (Temnothorax albipennis) showed any lateral bias.
In one experiment, scouting ants from eight colonies were observed while exploring a brand new nest. Groups of scouts turned left in 35 cases after entering the nest, and right in 19.
The second test involved a maze with lanes that branched out into two-pronged forks. From the second fork onwards, the ants opted left more often -- 50 times compared with  30 right turns.
"No scientific experiment is ever conclusive but we think this is good evidence for a left-turning bias by usual statistical standards," study co-author Edmund Hunt of the University of Bristol told AFP.
And the observed bias was strong enough to be "significant at the population level", the study paper said.
The authors theorised that such lateral preference would reduce the predation risk of individuals, resulting in most members of the colony herding together in the same place.
"The ants may be using their left eye to detect predators and their right to navigate," Hunt added.
"Also, their world is maze-like, and consistently turning one way is a very good strategy to search and exit mazes."
Source: AFP