978 - 0 - 521 - 19342 - 9 - Passive Acoustic Monitoring of Cetaceans

Since antiquity humans have been fascinated by whales and dolphins. They were attracted by the social behaviour and apparent curiosity of dolphins, which resulted in frequent interaction with humans. Myths were generated, especially around large whales, which behaved differently from other sea fauna. Even if early research on whales may have been driven by the economic interests of the whaling industry, the widespread recognition that whales, dolphins and porpoises are marine mammals significantly changed the scientific impetus. In fact, cetaceans (whales, dolphins and porpoises), together with the sirenians (manatees and dugongs), are the only mammals that live all their life in the sea. For an air-breather, living in the water is a continuous challenge and as such marine mammals deserve our respect and our protection. Consequently, in addition to a pure interest in knowledge, scientific research increasingly studies marine mammals to support their conservation and protection. Studying the life of marine mammals is a challenge for scientists, who may prefer a laboratory environment to the sometimes hostile sea, and most research in the past was limited to observations of surface behaviour. Only a few scientists were properly equipped to study the underwater behaviour of marine mammals. Studying pinnipeds (seals, sea lions and walruses) and sirenians was somewhat easier as these animals are sometimes accessible near shore: pinnipeds spend some time on land and sirenians live in very shallow water or rivers. Most cetacean species, however, occupy the vast areas of the oceans of the world. Living all their life in water, cetaceans have not only adapted their lifestyle, but have also modified the way in which they interact with each other and with the environment. In particular, cetaceans’ sound generation and auditory systems evolved and adapted to their new environment, basing their daily life mainly on acoustics. Apart from being essential for cetaceans, this use of sound allows human researchers to eavesdrop and to study cetacean behaviour from a distance. Although cetaceans are found in all oceans, they are highly mobile and most species that are of special concern to environmental management or are of public concern could be considered as rare or elusive. Classic cetacean surveys have used visual (sighting) methods to detect the animals, but there is growing recognition that many species of interest are easier to hear than to see. Owing to technological progress, there is now increasing awareness in the biology community about the usefulness of passive acoustic monitoring (PAM) for the study of cetaceans in their natural environment. PAM is a good technique for surveying and studying cetaceans, not only because they frequently use