Early in 1962, the behavior of the gray whale (Eschrichtius glaucus) was observed on its calving grounds in Baja California del Sur, Mexico. At the same time the Pacific bottle-nosed dolphin (Tursiops gulli) was also seen. Sounds made by both species were recorded with an AN/PQM-A1 Noise Measuring Set and Ampex 351, 2-Channel Tape Recorder. The frequency response of this equipment was from 40 to 20,000 cps ±2 db. Within this range the gray's sounds were heard from the lower limit up to 700 cps, with the greatest concentration of energy from 80 to 300 cps. Pulses lasted for 0.10 sec on the average and occurred in groups of 4 to 6. Tursiops were heads to echolocate with their characteristic -clicks- and to whistle. It is not likely that the gray whale uses echo-location with the same well-defined precision as the bottle-nosed dolphin.
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