Morphological changes during body development measurements are crucial in understanding growth rates, allometric relationships, and sexual dimorphism. Recent advances in drone technology provide a new perspective enabling an indirect, non-invasive morphological assessment of free-ranging cetaceans. In this study, 10 body parameters were measured and examined with drone-based aerial photogrammetry across 82 individual fin whales (Balaenoptera physalus) along the Catalan coast of the Northwestern Mediterranean Sea, between 2021 and 2023. The growth pattern of each body parameter relative to the total length was determined as negative allometry. The developmental changes depicted that the head region at first decreases proportionally until the animal reaches approximately 14 m in length. Then, it remains constant until 18 m, subsequently followed by a relative increase. The difference in the growth rates among the sexes leads to a proportional shift between females and males approximately between 15 and 17 m in length. Overall, males exhibit a more rapid body elongation, along with moderate development of the other body parameters, while females display the contrary. The morphological parameters reveal insights into the population status dynamics and provide information on the reproductive status. These parameters are critical for the proper conservation and management of the local population of the species.

The fin whale is the only whale species regularly found in the Mediterranean Sea, with a year around presence. However, the aquatic environment and the whale’s diving behavior have posed challenges to studying this marine mammal. The increasing use of drones in cetacean research has significantly enhanced our understanding of the species. Drones provide the ability to quickly and discreetly fly over the whales, minimizing the disturbance, while capturing high-quality footage that enables the observation of their behavior and characteristic features used for identification, as well as supporting morphometric analysis. Additionally, drones can assist in collecting blow samples and guiding research vessels for closer, more effective approaches to conduct biopsies, collect fecal samples, or deploy tagging devices. This technological advancement has greatly contributed to a deeper understanding of fin whales, offering valuable insights into the health of the population.