Article written by Jaz Henry. He studies English Literature and Philosophy and always thought the world of marine conservation was slightly out of his grasp, not having studied Biology or Zoology. So, this summer, he decided to let experience decide whether pursuing this line of work is the right choice for him. After applying to various projects, he was accepted as an intern for the Namibian Dolphin Project. This is the fourth and last post in a series of articles recounting his weekly experiences as a humanities student in a world of science and conservation.
My final week on the project was another week to remember and once again yielded one experience after the next. Tess Gridley replaced Simon as team leader for the last two weeks and brought a new, but equally fascinating perspective to the work the NDP does. Her focus is on bioacoustics and as such I have gained a more focused and in-depth understanding of the importance and relevance of acoustics in marine mammals. We have been deploying a lot of hydrophones, and beyond knowing that they record the noises dolphins, whales and other ocean dwellers make, I had not extensively thought about how that information is used. Tess explained to me that acoustics can be used for a range of applications, from revealing the changes in biodiversity in different regions by analysing the level of acoustic commotion in those areas over time, to recognising the different ways in which cetaceans and other sea mammals communicate. It can also reveal the effects and extent of issues like noise pollution and tourism, which is fundamental from a conservation point of view.
The main focal point of Tess, Rachel and Darren’s work, is the acoustic repertoire of dolphins, and so naturally leans to the research of how these animals communicate. They use a spectrogram to visually depict the frequencies and duration of the noises made by the cetaceans which have been picked up by a hydrophone. They then categorise these sounds and try and associate the different categories with different behavioural patterns to understand what the dolphins are trying to communicate with the different noises they make. For instance, dolphins use clicks to identify their prey. The closer they get to their dinner, the more frequent the clicks become, because they are signals that bounce off the prey and back to the dolphin. When a dolphin is about to catch its prey, the clicks become so bunched together that it resembles a buzz to the human ear, and so this noise in the acoustic repertoire of dolphins has appropriately been coined a “buzz”. Another key feature of dolphin acoustics is their signature whistle. Each dolphin develops a whistle in their first year or so of life which is unique to them and acts as a name would to a human. A mother may use her signature whistle to locate her calf in the vast ocean should it have veered off course, and the calf might reply with its mother’s whistle or otherwise with its own signature noise, identifying itself amongst the crowd. The whistles tend to be longer than clicks and vary in frequency and can thus be seen as separate sounds on a spectrogram, giving each dolphin an identity. In terms of noise pollution, I witnessed what clanging doors sound like under water, from a recording of dolphins in captivity, and what a boat motoring along produces on a spectrogram and it is a shocking contrast to the fleeting and peaceful hustle and bustle of the dolphins.
Tess’ presence spurred on the development of a side project the NDP is working on: the “Jackalogue”. It consists of collecting all the data on the numerous jackals around Walvis Bay and creating a catalogue of each individual.
