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Zebra finches' ingenious 'vocal panting' cools them down and signals hot weather to embryos

By Alice Walker and Beth Gibson, Friday December 4, 2020 - 12:03 EDT
ABC licensed image
Zebra finches use 'vocal panting' to cool themselves down in hot weather, researchers have found. - ABC licensed

As this latest heatwave breaks records across Australia, we're being forced to adjust to new levels of heat.

What if you could increase your tolerance to heat just by repeating the phrase 'I feel hot'?

That is what zebra finches do, according to an ongoing study from ecology researchers at Deakin University.

The zebra finch is an Australian bird with a distinctive red bill commonly found in hot dry areas around Australia, including northern Victoria.

"They are in groups usually, and they are really talkative. So normally you hear them before you see them," said research lead Mylene Mariette from the Centre for Integrative Ecology.

The original component of the study found that zebra finches made a special, high-pitched 'heat call' when incubating their eggs in hot conditions, usually when the nest reached more than 29 degrees Celsius.

Dr Mariette said the team found the embryo tended to grow less when subjected to the heat call.

"You produce a lot of heat when you eat a lot and grow a lot," Dr Mariette said.

"So reducing growth when you are going to be very hot is actually a good strategy [for reducing heat]."

Dr Mariette said they also found that embryos that reduced their growth went on to produce more babies when they were adults.

"They were healthier because they had not grown so much in very hot conditions," she said.

Dr Mariette said the special call sounded a bit like crickets.

"It's really high-pitched and really fast, and it follows their respiration rates," she said.

Vocal panting also helps parents

The team's latest study, published last month, found the heat call was not only designed to signal hot weather to embryos, it also helped keep the parent birds cool.

Dr Mariette said birds, in general, pant to keep cool rather than sweat, and some vibrate their throat or respiratory tract to further increase the amount of water released.

"So it's like dogs basically, and what they do is release water to reduce body heat," Dr Mariette said.

"So we thought perhaps the heat call is coming from a special form of panting where the birds would be vibrating a path from the respiratory tract ? that would create the sound and at the same time change their circulation so they cool down more."

To test the theory, the team exposed some birds to increased temperatures in a metabolic chamber and measured the amount of energy and water used when resting, panting, and heat-calling.

"We found that when they go from panting to panting and calling, they increase the amount of water that they lose," Dr Mariette said.

"The ones that call more are better able to sustain really high temperatures for longer."

Dr Mariette said it was the first study to show how vocalisation can help birds to survive heatwaves.

The team is now investigating whether other birds also use 'vocal panting'.

"It makes sense that zebra finches would because they are mostly in the hotter parts of Australia," Dr Mariette said.

"But there are lots of other small birds that likely also do this for communication with embryos."


© ABC 2020

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