Where are the great marine animals of the Mediterranean, such as the fin whale, the sperm whale or the bottlenose dolphin? How does their distribution change over a few weeks? All indications suggest that these species shift between marine areas in a remarkably short time and over relatively small spatial scales. Some species, such as the striped dolphin, maintain a relatively stable presence in certain areas, while others, such as the fin whale, move and concentrate in different areas from one observation campaign to the next.