Some Aussie frogs raise pitch of love songs to counter traffic noise

Washington, Aug 26 (ANI): Some Aussie frogs often raise their pitch as they serenade their partners, in order to counter traffic sounds, according to a study.

Kirsten Parris, an ecologist at the University of Melbourne, says that one species of frog in Melbourne is changing the pitch of its love song to be heard above the roar of the road.

For the study, Parris visited many urban ponds and pools inhabited by frogs, measuring traffic noise, which is, unfortunately, at the same low frequencies as many frog mating calls.

But, for the onomatopoeic 'pobblebonk' (Limnodynastes dumerilii), she found that a call that could originally be heard by a female 800 metres away might only carry 98 metres above 60 decibels of traffic noise, an average value for Melbourne.

She has also discovered that the southern brown tree frog (Litoria ewingii) seems to be compensating for the traffic noise by increasing the pitch of its calls1 (listen to before and after calls).

Parris suggested that installing noise barriers at strategic points around a road could help urban frogs to hear each other.

She further said that creating habitats where they thrive - such as ponds with sloping rather than steep sides - would also make sense.

"Cities provide some of the last habitat for a range of frog species around the world. So if we only worry about conserving frogs and their habitats outside cities, some of these frogs may well go extinct," she said.

She added: "Some frog species are very sensitive to environmental changes", but "others are quite adaptable and can persist in urban habitats if we gave them a bit of help".

However, Kris Kaiser, an ecology graduate student at the University of California, Los Angeles, has put forward a note of caution on the subject of these amphibians' adaptability.

"Frogs, unlike birds, are thought to have the frequency of their calls somewhat constrained by their anatomy. There is often a relationship between body size and frequency of call," he said.

Thus, he claimed that the creatures' ability to compensate for traffic noise may be limited.

The study was presented at the International Congress of Ecology in Brisbane. (ANI)