Distinguishing between adult and calf harbour porpoise clicks: A pilot study in the Dutch Oosterschelde

Research output: Book/ReportReportProfessional


The aim of this pilot project is to investigate whether and how harbour porpoise clicks can help us to identify the presence of calves. This would be a first step to developing detection methods applicable to hydrophone data that can identify behaviours and/or calf presence. A method was developed and experimented to record calf clicks, by actively searching for calves on the Oosterschelde and recording their clicks while close. Five field trips were conducted over the summer of 2021. Finding harbour porpoises was done with the help of Rugvin Foundation and was successful, but finding calves proved a bit harder. Moreover, calves always occur in close vicinity of their mother, so isolated recordings of calves were not made. However, differences in vocalisation characteristics were found in conjunction with sightings with and without calf, but this aspect needs to be validated with more replication. More data is thus necessary for further conclusions. The Oosterschelde proved a suitable and accessible research area, with a very high chance of harbour porpoise sightings. This is an ideal area for developing, finetuning and replicating scientific methods. A second goal of the project was to conduct outreach activities, bringing our research and the harbour porpoise a bit closer to the Dutch public. Two short movies were developed about the project, which were well received. Moreover there was an item about the research on the popular radio program ‘Vroege Vogels’.
Original languageEnglish
Place of PublicationIJmuiden
PublisherWageningen Marine Research
Number of pages36
Publication statusPublished - 2022

Publication series

NameWageningen Marine Research report


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