Dr. Jack Terhune studied seal communication at the University of New Brunswick and has measured the amplitude of seal calls. His research has shown that harp seals, often living in groups of up to 150, can alter the pitch of their calls so that each seal can be heard. Off the coast of Newfoundland, there are between 5.5 and 6.5 million harp seals in regular migration up and down the eastern seaboard. One seal’s call could be heard by 10,000 other seals at a range of two to four kilometers away, so the changes of pitch and frequency are important to avoid overlap.