17.01.2020 – Airborne prey

While local fishermen in Madeira are set on catching Bigeye tuna (Thunnus obsesus), another type of fish is in season for dolphins; Halfbeaks (Belone belone). These epipelagic fish got their name from their distinctive non-mobile lower jaws that extend far beyond their mobile upper jaws and typically dwell in schools just below the water’s surface, making them a popular prey for a variety of predators. They tend to occur in abundance at this time of the year and their presence is indicated by the behaviour of one of their most voracious predators during our tours, the Short-beaked common dolphins (Delphinus delphis). 

When these decorative dolphins hunt Halfbeaks they do so in small, compact formations usually consisting of a handful of animals. As with all their hunts, the dolphins use simple but effective group strategies. While some animals confuse and intimidate the fish, one of the animals swiftly leaps upward, propelling the terrified fish out of the water. The poor fish that involuntarily went airborne during this attack experiences a brief state of shock, during which the dolphin delivers the coup de grâce. Such scenes are extremely exciting to observe and the commons supplied us with a few these epic situations on both trips today.

The enormous area containing the dispersed group of common dolphins this morning was breached shortly after by an equally large pod of Bottlenose dolphins (Tursiops truncatus). These animals seemed less interested in Halfbeaks and more preoccupied with their journey eastward but briefly approached our Stenella to take peek at us. As the group approached, a larger dolphin could be identified by our crew as an individual who was also seen last year and was easily recognisable due to its signature bubble trail at the surface and its distinctly marked dorsal fin. This ID made the Bottlenose dolphin sighting just as eventful and exciting as that involving the commons, so it’s safe to say that our day on the ocean was quite wonderful today.

By Paula Thake

Sightings of the day

Stenella

10:00 Bottlenose dolphins, Short-beaked common dolphins

15:00 Short-beaked common dolphins