BIOACOUSTICS

In 1968, Dr Payne and Scott McVay studied the intricate vocalizations of humpback whales. They realized that they were hearing fixed rhythmic patterns of repeated sounds or songs. Although many other whale species also sing songs and make a variety of noises the humpback has the longest and most complex songs.

Since this discovery Dr Payne and colleagues at OA have gathered songs from humpback populations throughout the world. The Alliance's Whale Song Library now contains more that 1,500 recordings from fourteen different geographic regions. The library totals more than 6,000 hours of sounds and constitutes the largest collection of humpback recordings.

Katharine Payne discovered that all the humpback whales in an area sing versions of the same song which change throughout the course of the season. Following this, Alliance scientists have discovered that although humpback whales in the Atlantic and Pacific follow the same rules to construct their songs, that their songs are different. Songs can therefore be helpful in delineating interbreeding stocks of humpback whales.

Recent data from the US Navy confirms Dr Payne's 1971 theory (with Douglas Webb) that some whale species make sounds that can be heard over hundreds or even thousands of miles. Recent analysis of low frequency sonar data has proven that Payne and Webb were correct - by utilizing the special acoustic properties of deep water the sounds of whales can carry for great distances.

Such long-range signals may serve as beacons when whales are trying to find each other or their isolated breeding grounds. Unfortunately, the invention of propeller-driven vessels has probably interfered with whales' long-range communications.

From the RV Odyssey the Alliance is extending its study of whale bioacoustics. Using hydrophones and two acoustic arrays towed beneath the vessel, Institute scientists digitally record whale vocalizations. With software developed by the Laboratory of Ornithology at Cornell University, each vocalization will be converted to a spectrogram and catalogued in a database. These spectrograms may then be compared to those of whale vocalizations recorded in regions throughout the world. The towed arrays make it possible to count the number of vocalizing whales heard from the vessel. Comparison of this number with the number sighted will enable OA researchers to calibrate the technique of acoustic census taking by comparing the number of whales heard with the number sighted.