Researchers at Dartmouth College, New Hampshire, United States, have discovered a frog species (Rana sylvatica or Wood frog) that form singing bands or boy bands that sing to attract females for mating. Studies have shown that females are allured to low-frequency sounds because they indicate their mates’ good physical health and bigger bodies. Therefore, males find their band members that have low sound frequencies to increase their chances of mating. A frog chorus includes individual sounds of different frogs that make a bizarre gobbling and quacking noise.
“A chorus of wood frogs can sound a lot like the chaotic gobbling from a group of rowdy turkeys,” said Ryan Calsbeek, study author. “No one has figured out a way to extract the voice of one individual from a chorus to understand how membership in a group influences that individual’s chance at getting a mate.”
Wood frogs have a broad range over North America and reproduce in temporary water bodies, unlike ponds and lakes. The species can withstand cold and move to thaw pools to breed in early spring. Numerous male frogs form groups or armies and sing together to impress females. Once a female enters the area, males compete to make a mating pair. It is believed that females aspiring to reproduce associate different body types with high or low-pitched sounds of their partners. For instance, low pitched voice with a giant frog.
Researchers used an acoustic camera to locate the sound sources at ponds to determine the individual contribution to the frog band. The camera consists of an antenna on a pole, and directional microphones point out the sound source.
“The camera allowed us to analyze individual calls as well as group dynamics,” said Laurel Symes, the study’s co-author. “This is the audio equivalent of picking out the trees from the forest.”
The experts then laid heat maps of sounds over videos of breeding ponds to determine the activity of frogs and matched them against areas having eggs as a sign of breeding. The results indicated that females weren’t interested in individual male voices but seemed to be attracted to a group of male frog choruses having a collective low-pitched sound frequency. As male body size determines the audio frequency, more varieties of choruses inform females that there are males of different sizes in that group. Interestingly, males can choose whether to sing with frogs of different or exact body types based on their ability to influence the female for mating.
“It seems that the chorus calls are used to attract the female wood frogs to a breeding site,” said Calsbeek. “The individual songs play a role in positioning the male frogs within that site, but it then becomes a physical showdown to decide who mates.”
According to the researchers, the effect of factors such as climatic conditions and predation on determining the connection between mating and singing is yet to be discovered.
The research has been published in the journal Ecology Letters.