Killer Whale Boat Surveys
Boat surveys of Antartic and adjacent waters in the 1970s and 1980s, documenting killer whale color patterns and geographical variablility of killer whale vocalizations. Researchers assessed the range and abundance of killer whale pods to understand the ecological role of these whales. Distribution records, photographs of color patterns and recordings of underwater killer whale vocalizations were taken during various ship transects.
Strong geographic differences were found in all four types of vocalizations (clicks, buzzes, screams, and whistles). Clicks ranged from 500 hertz (cycles per second) to 30 kilohertz, exhibited 10 to 30 pulses per second, and most commonly were given in doublettes. McMurdo animals called at higher frequencies than the 6 kilohertz reported for Newfoundland killer whales. In Newfoundland the first pulse of a doublet was lower in frequency than the second pulse; however, this was not observed at McMurdo.
Buzzes (click bursts) were highly variable, with the major energy below 5 kilohertz; pulse rate and emphasized frequencies at McMurdo averaged much higher than in Newfoundland.
The scream was the most distinctive vocalization of the Southern Hemisphere whales. Screams were tonal frequency sweeps from 16 kilohertz through 500 hertz, with high energy harmonics and abrupt shifts in pulse rate. The whistle of McMurdo whales was very similar to those of killer whales from other areas. However, whistles seemed to be a more prevalent part of the McMurdo repertoire. It is uncertain whether the geographic differences reflect biological differences or adaptive responses to ambient background conditions.
