Frogs inform hearing aid research

A four-year-long University study found that multitasking male frogs are more likely to attract mates.

Katelyn Faulks

University of Minnesota researchers have found that the more successful a male is at multitasking, the more attractive he is to females — at least among frogs.

Male gray tree frogs can vary how long, how loud and how fast their mating calls sound to females — a process researchers refer to as “multitasking.” In the study, females favored males who were better at this process. This research from the University of Minnesota, published in the August issue of Animal Behaviour, could help improve hearing aids because the way female frogs distinguish male calls is comparable to the way humans decipher sounds.

Currently, hearing aids can’t control the focus of a person’s hearing. They can amplify sounds but don’t always allow a person to hone in on one voice from a group.

Scientists call this the “cocktail party problem.” The study shows female frogs can pick out each male mating call individually from a group.

“We are learning how the [human] brain separates signals from their [pitch and tone] patterns,” said Peggy Nelson, an associate professor at the University who specializes in audiology and hearing aid signal processing. “That’s specifically what frogs are doing.”

The study suggests female frogs can perceive the changing pitch and pulse rates of one male frog even among a group of calls. This may help scientists understand how humans can focus their ears on one another’s voices, Nelson said.

“Perhaps our sensory aids can have greater abilities to pick out those patterns,” said Nelson.

Postdoctoral researcher and lead author of the study Jessica Ward said she was hoping to find out if male Cope’s gray tree frogs multitasked and if female frogs preferred males that multitasked.

Researchers collected 1,000 frog calls during the course of four years. They found that males have to balance chirping rhythm with call length, which is difficult to do at the same time. But male frogs that could multitask were more popular mates.

Notably, males didn’t try harder to multitask when competing for female’s attention. The researchers found call length increased only slightly when other males were around.

“If males want to make themselves more attractive than competition,” Ward said, “they would boost effort to make calls more attractive. Male frogs produce 20 to 40 chirps per call and make five to 15 calls per minute. PhD candidate and study co-author Lisa O’Bryan helped record the mating calls.

But when male frogs project their calls to attract females, they can also attract unwanted attention from predators.

“It is very important to recognize that evolution interacts with many checks and balances and tradeoffs,” said Marlene Zuk, a University professor who specializes in sexual selection and animal communication.

Zuk said frogs and humans could potentially benefit or be hindered from performing multiple tasks to impress a mate.

“In addition to being flashy to potential mates,” she said, “you could be flashy to rivals.”