THE CLICK-SOUNDS OF NARWHALS (MONODON-MONOCEROS) IN INGLEFIELD BAY, NORTHWEST GREENLAND

We studied the sounds of narwhals (Monodon monoceros) foraging in the open waters in Northwest Greenland. We used a linear, vertical array o f three hydrophones (depth 10 m, 30 m, 100 m) with a fourth hydrophone (depth 30 m) about 20 m from the vertical array. A smaller fifth hydr ophone (depth 2 m) allowed for registering frequencies up to 125 kHz ( +/- 2 dB) when signals were recorded at 762 mm/sec on an instrumentati on tape recorder. Clicks were the prevalent signals, but we heard whis tles occasionally. We separated the clicks into two classes: click tra ins that had rates of 3-10 clicks/sec and click bursts having rates of 110-150 dicks/sec. The spectra of train;licks had maximum amplitudes at 48 +/- 10 kHz and a duration of 29 +/- 6 mu sec. The spectra of bur st clicks had maximum amplitudes at 19 +/- 1 kHz and a duration of 40 +/- 3 mu sec. By analogy with other dolphin species, narwhals presumab ly use the clicks for echolocation during orientation and for locating prey. The narwhal click patterns resemble those of insectivorous bats . Click trains might correspond to bat searching signals and click bur sts to the bat's terminal ''buzz'', emitted just before prey capture.