Acoustic ecology of marine mammals in polar oceans

In polar habitats, research on marine mammals including studies of the possible ecological consequences of anthropogenic impact is hampered by adverse climate conditions restricting human access to these regions. Marine mammals are known to produce sound in various behavioural contexts, rendering (hydro-)acoustic recording techniques, which are quasi-omnidirectional and independent of light and weather conditions, an apt tool for year round monitoring of marine mammal presence and behaviour in polar habitats. Acoustic behaviour is shaped by the species-specific behavioural ecology, as well as by abiotic, biotic and anthropogenic factors of the animal's living environment, a concept known as acoustic ecology. Acoustic ecology thereby describes the interaction between an animal and its environment as mediated through sound. An understanding of the acoustic ecology is important when interpreting acoustic data, as the acoustic ecology of a species determines if physical presence results in acoustic presence, on which temporal scale acoustic activity occurs and over which spatial scales acoustic presence can be detected. This thesis comprises ten manuscripts/papers, which are based on acoustic data collected in the Southern and Arctic Oceans. All provide examples of how aspects of the acoustic ecology of the species shape acoustic behaviour. In addition, the majority of manuscripts/papers also illustrate how acoustic monitoring can provide information of physical presence of marine mammals in areas where prolonged visual observations are not possible. Acoustic ecology forms the overarching concept that braces these publications. Given the relatively sparse literature on this concept with respect to marine mammals, this synopsis includes a first detailed conceptual description of acoustic ecology for polar habitats. Particular emphasis thereby is given to the specific environmental conditions in polar habitats and the looming threats of climatic change and other anthropogenic influences.