14 DAY TRIAL // As in the dark you cannot rely on your sight, what can you do in order to find flying prey?
At this dilemma, bats responded by developing their sophisticated ultrasound hunting system.
But about 50 years ago, researchers found that moths, which form the basis of bats' diet, can hear the ultrasonic hunting calls of their nocturnal predator.
Moths have one of the simplest auditory systems in the insect world: they have only two or four vibration-sensitive neurons attached to a small eardrum.
But scientists had underestimated these simple ears, as being only partially sensitive to the sound frequencies commonly used by bats, and it would seem likely that by using higher ultrasound, bats would make their hunting calls inaudible to moths.
But a team at the University of Bristol (UK), led by James Windmill, proved that moths are not as deaf as they had previously been supposed to be.
In the new study, they show that the ear of the yellow underwing moth changes its frequency (pitch) sensitivity in response to sound.
As a bat gets closer to a moth, both the loudness and frequency of sound increase.
Surprisingly, the sensitivity of the moth's ear to the bat's calls also increases, as the moth ear dynamically becomes more sensitive to the frequencies that many bats use during the attack.
Furthermore, the ear remains tuned up in this way for several minutes after the sound stops, ready in case there is another attack.
This is an astonishing behavior and ability, which has apparently not been reported for insects, or in fact, for any other hearing system in the animal kingdom.
This finding changes our understanding of the co-evolution of bats and moths, which seems to be not so linear.
As the moth cleverly tunes its ear to enhance its detection of bats, how do the bats in turn modify their calls to avoid their detection by moths and to eat, in the end?
As bats are extremely varied, many surprises can show up investigating this issue.