…The miniature backpacks were developed by Mark Johnson and Peter Teglberg Madsen at Aarhus University in Denmark. Weighing about 3g, they included instruments that recorded altitude, acceleration and sound. The team placed the backpacks in party balloons to protect them, and used medical glue to stick them to bats, which weigh 40-60g. The bats, which were using roosting boxes that were regularly monitored, had already been fitted with tiny microchips to monitor their comings and goings…

…The bats descend at an average rate of 8m a second, but will accelerate in bursts to much faster speeds.

As in an aerial duel, the bat locks on and attacks, signalled by a rapid burst of echolocation pips. The birds, unable to hear the bat’s ultrasound calls, remain oblivious until the last moment…