Günter Tembrock, a young scientist at the Zoological Institute only wanted to try out a new tape-recorder when he took his microphone to a Berlin garden on Oct. 30, 1951. There he captured the voice of a wild tawny owl as it "chatted" with two caged birds inside his office.

That was the start of the Animal Sound Archive, a scientific documentation of animal voices as an expression of their behavior. The collection soon expanded when Tembrock worked together with assistants and students to record more animals at Berlin's two zoological gardens and later in the wild.

Today, the Animal Sound Archive at Humboldt University in Berlin is, with 110,000 samples, one of the oldest and largest collections of animal sounds in the world. It contains 1,800 species of birds, the world's largest collection of mammal-sounds, 150 species of arthropods, and various fish, amphibian and reptilian species.

It even has the only recording ever made of a mole.

Getting a feeling for the animals

Two thirds of the recordings were made in captivity and one third in the wild in central and eastern Europe, the Caucasus, Central Asia, Africa, Central America and the Antarctic.

The archive's director, Karl-Heinz Frommolt, said recording wild animals is never easy.

"I have no tricks," he said. "The best way is to sit and wait, and wait, and wait. You have to develop a feeling for the animals."

After studying one particular species for a long time, some experts get a feeling for when the animal might begin to vocalize, added the archive director.

A biologist himself, Frommolt specializes in wolves. After waiting for several wolves to appear, he would turn on his recorder and start talking with them.

"It's a great feeling when you howl and the animals answer you," Frommolt said.

Animal dialects

In Berlin, animal voices are used to research animal behavior. Why, for example, do birds sing?

"Birds mainly sing for two reasons," said Frommolt, adding that animals can distinguish each other by their voices. "They could be giving a territorial signal, or trying to attract a female. In most songbird species, only the males sing."

Birds often sing in "dialects," the biologist said, adding that they learn the various song structures from their parents and neighbors and -- since they are territorial -- they tend to return to the place where they were hatched.

Geographical variations can be heard in the calls of other species as well, like the red deer.

"The Wapiti in North America, which is a sub-species of the red deer, whistles," he said. "But no Englishman would say that a red deer whistles. He would say that they roar, and if you listen to the sound, you will know why."

Your phone is squawking!

The unique archive is housed in Berlin, but the recordings have become globe-trotters. Audio-installations in museums and zoological gardens around the world make use of them, and rare animal voices can be heard in the digital edition of Germany's well-known Brockhaus encyclopedia.

What's more, the voices of six endangered species can even be downloaded as mobile phone ring tones as part of an unusual environmental protection campaign called "Nature is Calling," which is sponsored by the German government.

The archive also combines nature with technology and makes use of the Internet to complete research in bioacoustics.

Researchers from the Humboldt University Animal Sound Archive have teamed up with computer science experts from Bonn University to investigate noise pollution.

"In Germany you can hardly find a place without noise pollution," Frommolt said. "I believe that this noise pollution could be a problem for the animals and I'm hoping the world will change."