25.06.2025 – Predator and prey

The Atlantic Ocean surprised our team with a colourful array of dolphin species, all with a different relationship to the waters of our beautiful archipelago. Among them, the Bottlenose dolphins (Tursiops truncatus) belong to the predators with the strongest site fidelity here in the region, with many coastal ecotypes belonging to a resident population that is shared with the Canary Islands. It makes sense that these highly active dolphins don’t remain in one place but roam a larger home range, allowing them to come and go as they please. The other two smaller species we encountered today are considered seasonal visitors in the islands waters, at least for now. The arrival of the Atlantic spotted dolphins (Stenella frontalis) is marked with an increase in water temperature as the hot summer months approach while the Short-beaked common dolphins (Delphinus delphis) are significantly more abundant during the winter months.

Despite the difference in site fidelity, the occurrence of all three species has one thing common; prey availability. This affects their general occurrence but also their distribution in the regions waters. In winter the common dolphins are seen hunting far offshore while in summer they remain closer to shore with their young calves. The spotted dolphins are almost exclusively seen in waters that are over 1km deep, where currents bring nutrients that affect their prey availability. Bottlenose dolphins prefer foraging in coastal waters and quickly move on if there isn’t anything interesting.

Of course, prey availability also affects the occurrence of other marine predators such as sharks. Today our team even encountered a Hammerhead shark (Sphyrna zygaena) gliding alongside a few spotted dolphins this morning! What a day!

By Paula Thake

Sightings of the day

Ribeira Brava

09:00 Atlantic spotted dolphins, Bottlenose dolphins

13:00 Atlantic spotted dolphins, Short-beaked common dolphins

Stenella

09:30 Atlantic spotted dolphins, Bottlenose dolphins, Short-beaked common dolphins

13:30 Atlantic spotted dolphins, Short-beaked common dolphins