Camille Rondeau Saint-Jean (DC8) certainly enjoys a challenge: developing her drone piloting skills by attempting to film harbour porpoises is no easy feat indeed. Although they are the most abundant cetaceans in Denmark, porpoises are notoriously hard to observe and study in the wild. They are fast, comparatively small, surface only briefly when to breathe, and they swim in unpredictable patterns. Additionally, Danish waters are often murky, which means that animals are obscured from sight as soon as they dive underwater.
Advancing Drone Techniques
However, thanks to the mentorship and experience of WildDrone collaborator Héloïse Hamel, the research team at the SDU Marine Research Center is improving techniques to find and follow porpoises with drones. Evaluating the health of individuals and predicting demographic trends thanks to drone data seems to now be within reach. But before they can collect data on wide populations and analyse it confidently, the researchers need to test their methods and confirm measurements on well-known individuals.
The Ideal Research Porpoise
NotchSure is a female harbour porpoise who goes against most of what makes her species so difficult to study. Instead of staying further offshore, she spends a lot of time near the harbour in Kerteminde and can sometimes even be seen directly from the SDU Marine Research Center. Also, unlike most porpoises, who do not often have visible individual features, she has distinctive notches on her dorsal fin, which explain her name, and she has a small scar on her back. Therefore, she can confidently be identified not only on regular photographs, but also on drone footage. One could hardly imagine a more convenient research porpoise!
NotchSure has now been observed in Kerteminde for nine consecutive years, each time bringing with her a new calf. Uniquely, in the summer of 2024, she has been seen pregnant on June 26th and then with a very young calf on July 1st, which allows for an exceptionally precise estimate of the date of its birth. Since then, Camille and her colleagues have been able to observe the pair every few days and named the calf Elvis. Camille has used a DJI Mavic 3 pro drone equipped with a LiDAR altimeter payload to film the pair.
Measuring Porpoise Growth
Using frames extracted from the videos and the very accurate altitude readings of the LiDAR system, which correspond to the distance between the camera and the surfacing porpoises, Camille is now able to use photogrammetry techniques to measure the body length and girth of NotchSure and Elvis. This is a unique opportunity to follow the growth of a calf and the evolution of the mother’s body condition in the weeks following birth.
Understanding Porpoise Health and Demographics
This project will help determine the growth curve of young wild porpoises, which will later allow Camille and her team to estimate the age of young individuals from a single observation. Furthermore, this exceptional data will enhance the current understanding of the body condition recovery of mothers after birth and during lactation. Overall, this unique set of observations is a steppingstone towards a more widespread use of drones to monitor the health and demographics of harbour porpoises in Denmark and around the world.
You can read more about Camille’s project here.
