"Inquiry calls allow bats to stay nearby while they are flying," Chaverri explained. "Inquiry calls are also used to inquire about roost location. When bats enter a leaf roost, if they hear an inquiry call, they start vocalizing response calls. Therefore, response calls announce roost location."
The leaves also distort the calls, but it remains unclear if that helps or hampers the bats. The speaker-like boost is definitely a benefit, though, according to the researchers.
They believe other bats might exploit natural resources for sound amplification, such as bats that roost in bamboo stems and those that go into tree cavities and rock crevices.
"These structures might act as resonators, which are known to amplify sounds in other animals," Chaverri said. "Some examples include burrowing frogs and mole crickets."
She added that many other organisms live inside the tubular leaves chosen by the bats. These include frogs, scorpions and various types of insects.
Mirjam Knoernschild of the University of Ulm's Institute of Experimental Biology told Discovery News that she agrees with the new study's conclusions.
Knoernschild said that the authors' "work on sound amplification by tubular leaves is a new and valuable contribution to the field of animal communication."
For now, it's a mystery as to how the bats discovered the communication benefits of particular leaves. Was it trial and error, just a fortuitous coincidence, or the brilliance of one or more smart bats?
Chaverri and Gillam indicate that they might try to solve this mystery in a future research project.