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Science Notes: Sparrows don’t sing the same old song; whiskers detect acidity, help catfish track prey

Sparrows don’t sing the same old song

A sparrow’s song may sound simple, consisting of little more than whistles and trills. But to the sparrows, those few noises can take on vastly different meanings depending on small variations in context and repetition, researchers have found.

In humans, the ability to extract nearly endless meanings from a finite number of sounds, known as partial phonemic overlapping, was key to the development of language. To see whether sparrows shared this ability, researchers at Duke University recorded and analyzed the songs of more than 200 Pennsylvania swamp sparrows. They found that the sparrows’ whistles could be divided into three lengths: short, intermediate and long.

The researchers then played the sparrows two versions of the songs – the original and a slightly altered one. They found that replacing a single short whistle with an intermediate one, for example, could significantly alter a bird’s reaction, but only if it came at the right moment in the song.

“Identical sounds seemed to belong to a different category depending on the context,” said Robert F. Lachlan, a biologist now with Queen Mary University of London and the lead author of the study.

The findings, published in Proceedings of the National Academy of Sciences, are part of a larger effort to better understand how human language evolved.

Whiskers detect acidity, help catfish track prey

Japanese sea catfish have an unusual advantage when hunting in pitch-dark waters, a new study reports: Their whiskers can detect minute changes in the water’s acidity.

John T. Caprio, a physiologist at Louisiana State University, was studying how chemical stimuli were encoded by a catfish’s taste system when he noticed a strong reaction from the whiskers. Further study revealed that previously undetected sensors on the whiskers were responding not to the chemical itself, but rather to the effect it was having on the water.

“It was changing the pH of the water,” he said, “and not by much.”

The researchers then placed the catfish in aquariums with hidden polychaete worms, their preferred prey. The worms release tiny amounts of carbon dioxide and hydrogen when they breathe, raising the water’s acidity (and thereby lowering its pH). Even in the dark, the catfish were drawn to the area with the worms. The researchers, who published their work in the journal Science, also observed that the fish located the decreased pH areas even when no worms were present.

“This fish is a swimming pH meter, and its accuracy was as good as pH meters I was using in the lab,” Caprio said. “If you drop the pH less than one-tenth of a pH unit,” he added, the fish’s sensors “start firing like machine guns.”

The sensors worked best in seawater with a pH of 8.1 or 8.2, the researchers said, suggesting they may become ineffective as levels fall with ocean acidification.

– New York Times