By Martina Rathke
he young male Humboldt penguin with the yellow tag on his right wing is a star pupil: He touches the coloured board with his beak for a full four seconds. After a clicking noise, there’s a tasty sprat from his trainer, Anne May as a reward.
May has been working with four birds at the Ozeaneum in the northern German city of Stralsund for the past several weeks, training them to react to certain stimuli. But the birds, separated from the rest of the flock, aren’t being taught tricks in order to amuse visitors.
The tests have a scientific purpose: Marine biologists from Germany and Denmark are researching penguins’ powers of hearing, with the goal of training the birds to be able to indicate whether they hear an audio signal on land or in the water at a later research stage.
As the world’s oceans have become increasingly crowded in the last few decades, the amount of underwater noise has also grown enormously: a ship’s propeller, for example, produces a constant drone. Anchors for oil rigs and wind turbines are drilled into the ocean floor, where mining companies are also digging for minerals.
“The problem of noise is similarly as bad as the problem of rubbish for [the health of] animals, but the public is not nearly as aware of it,” says Harald Benke, director of the German Oceanographic Museum.
It is not yet known what effect underwater noise has on penguins’ hearing and whether it confuses the birds when they travel the world’s oceans. In fact, scientists have only rudimentary knowledge about what frequency and volume of noise that penguins can hear.
Aside from a 1969 study on the hearing of African penguins on land, there have hardly been any scientific examinations of the subject, according to marine biologist Michael Daehne, who has been leading the project in Germany.
“In order to make predictions about what effect underwater noise will have on penguins in the future, we need to have some basic data to start with,” he says in explaining the motivation for the study.
During the three years that the project has been scheduled to run, the researchers want to develop audiograms – a graph that shows the range of hearing levels – for the different penguin species.
The birds won’t be sent to a sound laboratory for the tests, but instead they’ll later be put in sound booths on land and underwater, where they’ll be played various noises and audio signals.
The University of Southern Denmark, the Marine Science Center at the University of Rostock in northern Germany and the Natural History Museum in Berlin are also taking part in the study on penguins.
“Penguins are amphibious beings, living between two worlds – land and water,” says Daehne. Through evolution, penguins lost their ability to fly in order to better adapt to the waters of the ocean. They can spend long times at sea and efficiently hunt and move underwater.
“Like all birds, penguins don’t have an outer ear, and unlike mammals, which have three auditory ossicles, birds only have one,” says Daehne.
Sound waves spread at different speeds through the air and through the water, he adds, meaning scientists can assume that penguins hear noise differently on land and in the water. Exactly how is what they are hoping to find out during the course of their project.
As well as Humboldt penguins, native to South America, the researchers in Odense are also testing gentoo penguins, southern rockhopper penguins and king penguins.
“The Humboldt penguin’s learning curve is really steep,” says May of her charges, who rub up happily against her legs, stretching their necks to look up at her without hesitation. However, a lack of reserve should not be mistaken for intelligence, May adds, saying she doesn’t want to pass judgement on the brain power of her charges. – DPA
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