A+ A-

Scientists use statistics to differentiate African dolphin 'dialects'


Understanding how and when animal species use their environment is a fundamental ecological question and one that can be surprisingly difficult to answer, particularly when working in the marine environment.

The waters around southern Africa host a high diversity of marine life, including many species of dolphin. One way to monitor where dolphins are and at what times, is to 'eavesdrop' on their environment and listen out for the vocalisations they make. As most animals make sounds, this process – called passive acoustic monitoring, or PAM – is increasingly being used to study a variety species, from frogs and bats to elephants. Dolphins make many different sounds, producing whistle and echolocation-click vocalisations throughout their day to interact with each other and their environment. Consequently, acoustic monitoring of dolphins can be a relatively cheap research method. We can use acoustic monitoring 24 hours a day for months at a time, by deploying many remote underwater microphones called hydrophones. 

However, for this kind of monitoring to work, we need to know what sounds each species makes, and there is a remarkable lack of information on this in southern Africa. Researchers from the University of Pretoria and the University of Cape Town have been working together to solve this problem using acoustic data collected from several dolphin species around southern Africa. The research, led by Ms Florence Erbs from Sea Search, Dr Tess Gridley from the University of Cape Town, and Dr Simon Elwen from the University of Pretoria, was published in April 2017 in The Journal of the Acoustical Society of America. Erbs and her colleagues used a statistical approach to grouping the dolphin sounds. First, they broke up the whistle sounds into small fragments and looked at their characteristics in terms of pitch (frequency) and the shape (curvature) of their contours. As there were thousands of whistles, this was done with the help of a freely available piece of acoustic software called PAMGuard which was then used to classify the dolphin sounds into groups. Although this method has been used to classify the sounds of dolphins in the northern hemisphere, this is the first time it has been tested on data from southern Africa and the researchers report that the trials were very successful. Three dolphin species commonly seen in southern African waters could be easily recognised using this method: the common dolphin, the Indo-Pacific bottlenose dolphin and the common bottlenose dolphin. Recordings of the same species made in different regions (Plettenberg Bay in South Africa and Zanzibar Island in Tanzania), showed that the software could even be used to recognise different dolphin populations, similar to the way groups of people can be differentiated based on their dialects.

This work is part of an ongoing study looking into dolphin occurrence around southern Africa and the possible impact of climate change on where and when dolphins are found. The E3C project (Effects of Climate Change on Cetaceans), as it is called, is led by the Sea Search group (www.seasearch.co.za) and associated university-based scientists, using several underwater hydrophones to record dolphins. It is funded by the National Research Foundation, the University of Pretoria and the Claude Leon Foundation.

Another aspect of the project is documenting where and when members of the public see whales and dolphins. We invite members of the public to be part of this by becoming 'citizen scientists' and logging their sightings on our dedicated Facebook page or Twitter account (@seasearchafrica), or by contacting info@seasearch.co.za.

 

More about the authors:

Ms Florence Erbs is an independent marine mammal scientist, working in association with Sea Search Research and Conservation, a Cape Town-based non-profit organisation focused on the conservation of cetacean species.

Dr Simon Elwen, who is overseeing this NRF-funded E3C project, is based at the Mammal Research Institute at the University of Pretoria. He co-directs Sea Search Research and Conservation.

Dr Tess Gridley, who leads the acoustics elements of this E3C project, is based at the Centre for Statistics in Ecology, Environment and Conservation, in the Department of Statistical Sciences at the University of Cape Town. She also co-directs Sea Search Research and Conservation.

 

 

Privacy Policy

The University is firmly committed to protecting the privacy of users of the website. No personal information about users of this website will be disclosed to a third party without the prior consent thereto by the user. (Personal information shall at all times be dealt with in accordance with the provisions of the Protection of Personal Information Act, 2013 (Act 4 of 2013).)

The University reserves the right to automatically collect information on users' usage of the website (for example, via cookies) in order to improve users' browsing and interaction with the University and for non-personal statistical purposes.

Changes to this privacy policy

The University reserves the right to change, amend, or update this privacy policy periodically.

Modifications to the website

The University reserves the right to modify, change, amend or discontinue the website (or any part thereof) temporarily or permanently, without prior notice.

Links

The University may provide links to other websites or resources. This does not imply the University's endorsement of such sites. The University does not have any control over these websites and will, therefore, not be liable for any damages whatsoever arising from the utilisation of these websites by users.

The University does not prohibit third-party sites to link to publicly visible content on this website. However, it is expressly prohibited for any third party to frame any page on this website in any way whatsoever without the prior written approval of the University.

University of Pretoria proprietary rights

The copyright and other intellectual property rights (which include the University’s brand and logo), which are owned by or licensed to the University, existing in and attaching to this website, are the property of the University. These include but are not limited to text, content, design, layout, graphics, organisation, digital conversion and other information related to the website.

Users are granted a non-exclusive, non-transferable, revocable licence to:

  • access and use this website strictly in accordance with these terms;
  • use this website solely for personal, non-commercial purposes; and
  • download or print out or distribute content from the website, or any part thereof, solely for personal, non-commercial purposes, provided that all copyright and other intellectual property notices therein are unchanged.

Any reproduction of the content of this website, or a portion thereof, must include the following copyright notice: ©University of Pretoria. Users who wish to use the content from this website for commercial purposes may only do so with prior written permission from the University.

Disclaimer

This website is for information purposes only. No representations or warranties are given by the University of Pretoria (hereafter referred to as the University) regarding the accuracy of the information this website contains, any material this website provides for or any part of this website. Any reliance by the user on any information this website contains, any material this website provides for or any part of this website, is at the user’s own risk and the University shall not be liable in any way whatsoever in respect of the user or any other person, directly or indirectly, arising from the utilisation of the information this website contains, any material this website provides for or any part of this website.

The user hereby agrees that in the event of any dispute arising from the utilisation of this website in any manner, form or substance whatsoever, the relevant South African law will apply and the appropriate courts of South Africa will have jurisdiction.

Terms & Conditions

By accessing this website, the user hereby agrees to the following:

The use of this website is at the user’s sole risk. This website is provided on an "as is" and "as available" basis. The University gives no warranty that (i) the information posted on this website will meet the user’s requirements; (ii) the information posted on this website will be uninterrupted, timely, secure, virus free or error free; and (iii) the information posted on this website will be accurate or reliable.

Any material downloaded from or otherwise obtained through this website is utilised at the user’s own risk, and the user will, therefore, be liable for any and all damages of any nature whatsoever arising from such utilisation of the website.

Limitation of liability

The user expressly understands and agrees that the University shall not be liable for any damages (subject to the provisions of Chapter 2 of the Consumer Protection Act, 2008 (Act 68 of 2008) (even if the University has been advised of the possibility of such damages) resulting from: (i) the use or the inability to use the website; (ii) the cost of procurement of substitute goods and services resulting from any data, information or services obtained or messages received or transactions entered into through the website; (iii) unauthorised access to or alteration of the user’s transmissions or data; (iv) statements or conduct of any third party on the website; or (v) any other matter relating to the website.