Bhubaneswar: The underwater behaviour of the endangered Irrawaddy dolphins of Chilka Lake in Orissa will now be monitored with special hydrophones developed to catch their high-frequency "click" sounds.

The Chilka Development Authority, along with the Underwater Technology Research Center of Tokyo University, has developed the hydrophones that are being tested in the lake. The devices would help in chalking out long-term conservation plans for the endangered species, an official said.

"This is the first time that such a study is being conducted to observe the underwater behaviour of the Irrawaddy dolphins. The software for the hydrophones has been developed by Underwater Technology Research Center of Tokyo University," said Ajit Pattnaik, chief executive officer of the Chilka Development Authority.

Studies have found that dolphins interpret the meaning of the click sounds through its complex nerve system after the sound bounces off the objects.

The hydrophones are designed to capture the high frequency clicks which can travel through water at a speed of about 1.5 km/sec, which is 4.5 times faster than sound travelling through air.

These hydrophones have been designed to capture the clicks and underwater behaviour of the dolphins.

"These devices would help determine the responses of dolphins to approaching boats and noise from the boat and other sources. It will also help to develop protocols for dolphin watching," he said.

The data gathered from the devices would help in determining the size, shape, speed and migration behaviour of the dolphins in the lake, without disturbing them.

An MoU had been signed in 2006 to develop these devices and tests were also conducted before these complete devices were decided on. The Japanese scientists have now developed a set of eight devices with inbuilt software to interpret the data. The World Wide Fund for Nature is also collaborating on the project. IANS