Collaboration enables passive acoustic research throughout the Sousa teuszii range

Collaboration enables passive acoustic research throughout the Sousa teuszii range

Over the course of 2023 and 2024 a growing collaboration between CCAHD partners in Congo, Gabon, Cameroon, Guinea and Senegal and international CCAHD members based in the UK and Slovenia is providing exciting new data, tools and insights into Atlantic humpback dolphins (AHD).

Atlantic humpback dolphins are rare and dispersed in small isolated populations. They tend to occur in small groups, and are often very subtle in their behaviour, making them difficult to observe in the wild.  Small boat-based surveys in the shallow nearshore habitats preferred by AHD can be expensive and logistically challenging anywhere in the world, but especially so in remote areas of Central and West Africa. Even when successfully funded and implemented, boat surveys can result in many days spent searching for dolphins without detecting them.

Since its inception in 2020, the CCAHD’s Acoustics Working Group has been focusing on how to effectively use passive acoustic monitoring as a potentially lower cost, yet effective way of detecting AHD in areas where the species is known to occur, in order to understand whether there are any seasonal, diurnal, or tidal patterns to their presence, as well as in areas where they are suspected to occur, in order to determine whether more dedicated (boat-based) research and conservation measures are needed.  Although passive acoustic equipment can be expensive, and the human resources required to analyse the many hours/days/ month of data collected are considerable, passive acoustic monitoring can detect dolphin vocalisations around the clock and in weather conditions that would not permit boat surveys.

The main challenge for this effort has been the lack of ‘voucher’ recordings that can be used to link specific vocalisations to AHD and the other dolphin species that may occur in the same area.  Only once such a library of recordings has been collected will researchers be able to develop ‘classifiers’ that can be used to assign detections to AHD versus, for example, bottlenose dolphins, common dolphins or even manatees, which also vocalise and overlap in range and habitat with AHD.

To address this challenge, CCAHD partners are undertaking the following projects and collaborations:

Congo:  CCAHD Partners, Renatura have been working with Chelonia Limited to deploy bottom-mounted hydrophones called Fpods in four nearshore areas between Pointe Noire and the Loango Community Marine Reserves where their teams are conducting regular turtle track and nest counts.  Dedicated field agents conduct visual observations to link AHD sightings to specific times and locations when the Fpods are recording, which will allow Chelonia Ltd.  Director, Dr. Nick Tregenza, to extract the ‘voucher’ data from the recordings, and use these to help work toward a classifier based on the clicks and click trains that Fpods record.

Gabon:  Drs. Julie Oswald and Vincent Janik of the University of  St. Andrews visited CCAHD member Judicael Regis Kema Kema while he was working on his PhD at La Rochelle University to lend him and train him in the use of a hydrophone that can be used to make recordings from a boat during dolphin encounters. Regis and his team conduct regular coastal surveys during which they encounter both bottlenose and humpback dolphins, so hopes are high that he will be able to collect voucher recordings from both species.

Cameroon:  Drs. Oswald and Janik also lent a hydrophone suitable to make boat-based recordings to the AMMCO team in Cameroon. This was used to record vocalisations during a recent encounter with common dolphins, and Clinton Factheu, who’s PhD research focuses on passive acoustic monitoring of manatees, will look for future opportunities to deploy the unit during marine and coastal work in Cameroon.

Guinea:  Boat-based surveys focusing on AHD have been conducted regularly in Guinea as part of a 2.5 year long dolphin conservation project implemented by the CCAHD in collaboration with Biotope Guinea and the CNSHB and funded by the Mohamed Bin Zayed Species Conservation Fund. During the past two surveys in 2023 and 2024, the project’s lead researcher, Tilen Genov, was able to use his hydrophone to record AHD during observations.  These recordings will be analysed by the St. Andrews team as part of the wider regional effort.

Senegal: As part of a long-term dolphin research and monitoring project in the Delta Saloum, CCAHD partners, the African Aquatic Conservation Fund (AACF) team in Senegal has been deploying Fpods (provided by Chelonia Ltd) and SoundTraps (one unit provided by Ocean Instruments) in the since July 2021.  While Fpods focus on recording clicks, SoundTraps record dolphin whistles as well. By deploying the units side-by-side, it is hoped that the recordings can be analysed to link both types of vocalisations.  In 2024 the AACF team also started to use hydrophones provided by St. Andrews to make recordings from the boat during AHD and bottlenose dolphin encounters.  For more information see this 2022 report to the International Whaling Commission.

The collaborations facilitated by the CCAHD Acoustics Working Group are starting to pay off.  It is hoped that within the next year or two, the data collected by range country partners can be used in a Loro Parque Foundation-funded project to develop AI classifiers that will be able to work their way through hundreds of hours of recordings and detect AHD and other dolphin vocalisations.  Once this tool is developed, passive acoustic monitoring can be used in more (suspected) AHD range countries to provide more insight into the species’ distribution, habitat use and threats.

Stay tuned!