Cetoscope : an innovative material and software to observe the cetaceans in their wild environment

Continuous observations of non-human species allow us to study them and understand their activities, their interactions with their peers and their environment. They also allow us to assess their intelligence and adaptability, for example by describing their cultural transmission and/or detailing the innovative attitudes they display to attract a partner, capture prey or escape a predator. These observations are difficult to carry out for cetaceans in their natural environment, due to their high mobility and low visibility in the depths. However, visual and acoustic data are necessary to characterize individuals, their behaviors and their interactions. To meet this challenge, we designed and built the Cetoscope. Equipped with 6 cameras and 4 hydrophones, this tool makes it possible to identify cetaceans in the vicinity, record their vocalizations to complete their vocal repertoire, and reconstruct their trajectories in 3D. We also have developed a software to track cetaceans in 3 dimensions and provide metadata, such as time, estimated distances, type of sounds emitted. After designing such a tool, the next step was to calibrate the video cameras and hydrophones to check the synchronizations and reconstruct, a posteriori, the observed scenes, from the recorded data. Finally, we used this tool to track a group of bottlenose dolphins off La Réunion Island, Indian Ocean. Our results allowed us to identify the individuals in the group (adult/juvenile, male/female) and also to show that some individuals are vocal while others are silent. We showed that vocal dolphins play the role of scouts in the sense that they approach the Cetoscope to scan it and learn more about it. Our study will be used to characterize the impacts of human activities, in particular how these cetaceans react to whaling tourism. Eventually, we would be able to better understand how cetaceans perceive humans in their environment and assist in decision-making regarding approaches and observation of cetaceans in a context of increasing tourism. 

[1] Doh, Y., Ecalle, B., Delfour, F., Pankowski, C. Cozanet, G., Becouarn, G., Ovize, M., Denis, B., and Adam, O. (2023). Performance assessment of the innovative autonomous tool CETOSCOPE© used in the detection and localization of moving underwater sound sources. J. Mar. Sci. Eng., 11, 960. https://doi.org/10.3390/jmse11050960 

[2] Gillespie, D.; Palmer, L.; Macaulay, J.; Sparling, C.; Hastie, G. Passive acoustic methods for tracking the 3D movements of small cetaceans around marine structures. PLoS ONE 2020, 15, e0229058