From electronic bugs to real ones, methods for listening provide insights into communication and hearing

A new study by U.S. National Science Foundation-funded researchers on how members of the animal world sense and react to sounds provides insight into adaptations in communication that could be used in the development of adaptable hearing aids or limiting the impact of agricultural pests.

"By increasing our understanding of how animals perceive and respond to sounds — especially when those sounds are changing — this research could aid in developing hearing aids that automatically tune as a person walks from a movie theater to a crowded restaurant or other adaptive hearing and acoustics devices," said Jodie Jawor, a program director in the NSF Directorate for Biological Sciences. "It also highlights how agricultural pests can move into an area and capitalize on a new host, harming society in the process — think about a parasite of honeybees that hurts their populations and our food supply."

The study focused on the interactions between a species of fly (Ormia ochracea) and Pacific crickets, which are engaged in a sort of sound arms race. The fly can hear the mating chirps of the male cricket and uses the sounds to locate the male, in which the fly lays its eggs. The fly larvae feed on and develop inside of their cricket hosts, eventually killing them when they emerge. Some crickets in Hawaii have responded to this threat by changing the sounds they use to find mates — purring or rattling rather than chirping — but the flies still find them, and the researchers sought to understand how.

The research team, led by Norman Lee, an associate professor of biology at St. Olaf College, and Robin Tinghitella, an associate professor of biology at the University of Denver, used a series of lab experiments to test if this was a unique counteradaptation by flies in areas where both they and crickets have been introduced or if the flies had always been able to hear the alternative noises but not focused on them, as in their natural habitats such sounds would not have signaled a cricket.  The researchers found  that populations of flies from natural and non-natural habitats could hear the purrs, but the flies from areas where they have been introduced were more active in their response to the sounds. This represents a novel change caused by adaptation to a new environment, knowledge that could support advances in assistive hearing devices for humans and shows the growing number of interactions that drive how species communicate.