Marine mammals are an important sentinel species; they sit at a high trophic level (top of their respective food chains) and have a relatively long lifespan and so can be particularly susceptible to changes in the environment. That means that the population levels of marine mammals and the general health of individuals are usually good indicators of the overall health of an ecosystem. This, the fact that many species are endangered and a strong public fascination with marine mammals means that many species are a focus for conservation efforts and scientific research. I’m one the people who studies marine mammals, specifically the sounds they make and how we can use those sounds to answer questions on animal behaviour and conservation.
Whales are usually very vocal animals; different species produce sounds that range from a few tens of Hz up to a few hundreds of thousands of Hz- that’s multiple times above human hearing range (<20000Hz). These sounds perform important social functions and in some species (toothed whales) are used as a sophisticated biosonar, allowing animals to sense surroundings, hunt for prey and sometimes communicate. As researchers, we can also use these sounds to study animals. By placing hydrophones (underwater microphones) in the water we can listen for and record species which may be very difficult to visually spot on the sea surface. Various algorithms can be used to detect what species might be vocalising, and, if the right kit is deployed, determine where the animal is underwater.
This method of studying marine mammals is called PAM (passive acoustic monitoring). It wasn’t long ago that we were recording a few hours of harbour porpoises (which have amongst the highest frequency vocalisations) on specialised tape. Now we can record weeks of digital data on devices about the size of coke can. This blog is about the PAM technology I use in daily research and the tremendous leaps we’re making with it at the moment. Hopefully it will help inform young scientists or maybe even catch the imagination of people out there who are not aware of what a cross disciplinary science this is. I’ll be talking about programming, (MATLAB, Java and C), the kit we’re using and developing and various other bits and pieces. If you’ve got this far, thanks! Enjoy the blog.