Climate change may be giving frogs a helping hand in the language of love, a new study has found.
Researchers from University of California, Davis, have discovered that temperature plays a key role in shaping the sound and quality of male frogs’ mating calls, with warmer climes making for a “sexier” tune.
In the early part of spring, male frogs’ calls are typically sluggish. But as warmer weather sets in, their songs pick up the pace – a change noted by females looking for a mate.
“The song of frogs really depends on the temperature of the environment,” said lead author Julianne Pekny, a UC Davis graduate student in the Department of Wildlife, Fish and Conservation Biology when the study was conducted and currently director of conservation science with the Amphibian and Reptile Conservancy in North Carolina.
“As ponds warm, male frogs go from sounding slow and sluggish to faster and almost desperate. I can hear it with my human ears, and female frogs are also paying attention.
The study, the results of which were published in Frontiers in Ecology and the Environment, was conducted at Quail Ridge Ecological Reserve and Lassen Field Station, which are part of UC Natural Reserves.
Using microphones placed at the edges of ponds, Pekny recorded the love songs of Sierran treefrogs and compared them to changes in water temperature.
Crucially, the researchers suggest that females are not simply choosing the most attractive singers, but are using call quality as a cue for whether environmental factors are suitable for breeding.
“What’s interesting to me is this could be a process by which females are tracking how seasonality is changing over time,” Pekny said. “As the pond warms, the sexier male calls come earlier, too.”
This dynamic could have important implications as the climate warms. With 41 per cent of amphibians being threatened with extinction, understanding when frogs breed – and how those timings shift – is critical for conservation.
Males usually arrive at ponds earlier than females and begin calling as early as possible to compete with rivals. Females, however, delay their arrival until conditions are right for their eggs to survive – information they appear to glean from the quality of the males’ songs.
“It’s in the best interest for males to get to the pond as early as possible, before other males,” said coauthor and herpetologist Brian Todd, a professor in the UC Davis Wildlife, Fish and Conservation Biology department. “But it’s in the best interest of females to get there when it’s actually time to go and lay their eggs.”
The team says the findings could reshape how scientists understand animals’ responses to climate change, and could have implications for insect species that similarly produce mating calls around this time of year.
And it’s not just the frogs who get to listen to these sultry sounds – humans can hear them too.
“If you can listen over the course of weeks or longer, see if you can notice the difference,” Pekny said. “Imagine how the female frog might perceive those male calls at the beginning of the season versus toward the end.”
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