Cali Owings, Published October 29 2013
NDSU researcher studies bat species that uses leafy roost as a megaphone
North Dakota State University researcher Erin Gillam has studied the communication system of this highly specialized bat species in Costa Rica for several years.
Gillam and her research partner – Gloriana Chaverri from the Universidad de Costa Rica – noticed the horn-like shape of the bats’ temporary homes. The pair analyzed the acoustic properties of the leaf to determine its role in the bats’ communication system.
Their latest research, published this month in the journal Proceedings of the Royal Society B, focuses on how the bats’ nesting space amplifies calls so group members can find each other.
“That’s potentially beneficial. It could just make the whole system more effective,” Gillam said. “It’s more likely that who you’re trying to call to actually hears you.”
The pair began studying the bats’ communication system to understand how such a mobile group could stay together.
“You’d expect that groups that move around so much mix and match who they’re living with,” Gillam said. “But that’s not the case. They will stay with the same group of bats for years.”
Some bats have been known to maintain associations for up to two years, she said.
During previous field studies, Gillam and Chaverri identified two calls the bats use to locate members of their group – an inquiry call from the flying bat and an answer delivered by the bats in the roost.
“When they’re separated, they’re able to find each other and these social calls appear to play a very pivotal role in that process,” Gillam said.
Recognizing group members
In their most recent study, which Gillam admitted was less fun because she didn’t get to handle bats, the pair played the calls through the leaves to see how the shape of the leaf affected communications.
They found both types of calls were amplified by the leaf, but the sound was also distorted.
Despite the distortion, “field experiments demonstrate that flying bats are capable of discriminating between the response calls of group and nongroup members,” Gillam and Chaverri write in the study. They speculate the calls are so complex that they are still recognizable after distortion from the leaf.
In continuing their work with the species, Gillam and Chaverri will next investigate how the bats determine which leaf will make the best roost and if sonic properties are a factor.
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