Bats obey their own 'traffic rules' when looking for food

Foraging bats obey their own set of 'traffic rules', chasing, turning and avoiding collisions at high speed, reveals a new research.

The findings could have application in rescue missions, monitoring tasks and surveillance operations, the researchers said.

Marc Holderied of the University of Bristol and colleagues studied pairs of Daubenton's bats foraging low over water for stranded insects.

Bats perceive their surroundings by emitting loud and high-pitched biosonar calls and listening for the returning echoes.

Because bat biosonar imaging is much sparser in information than vision, Holderied was able to accurately measure the biosonar calls of the interacting bats and then calculate what each of the individuals perceived.

The results indicated that bats obey their own intriguing set of 'traffic rules' - they chase each other, perform tandem turns and even slow down to avoid collision.

Holderied and his colleagues modelled the bats' biosonar view of their surroundings during these interactions and discovered that one simple trick suffices to create all the bats' interactive behaviour.

They swap leader-follower roles and perform chases or coordinated manoeuvres by copying the heading a nearby individual was using up to 500 milliseconds earlier (as fast as the blink of a human eye).

"The bats seem to have adopted a simple trick: once another individual is close enough for your biosonar to pick up its echo, copy this individual's flight direction within four to five of your own wingbeats," said Holderied.

Quantifying the movement decisions that bats adopt to forage has implications well beyond animal ecology.

"By employing movement strategies that nature has optimised over millions of years engineers may be able to improve the efficiency of search and rescue missions, monitoring tasks and surveillance operations in the emerging market of flying drones and autonomous moving vehicles," co-researcher Luca Giuggioli noted.