05.08.2018 – Anywhere, anytime

Our guests often ask us at which average distance we encounter marine mammlas during our tours. While many sightings occur at a distance of around 4 nautical miles off the coastline, the truthful answer is that animals can pop up anywhere at any given time.

Some species do, however, nurture a fidelity to certain areas. Bottlenose dolphins (Tursiops truncatus), for instance, tend to occur within two nautical miles off the coast while smaller dolphin species, like the Atlantic spotted dolphins (Stenella frontalis) are frequently encountered further offshore in much deeper waters.

While the random distribution of dolphins and their whereabouts can be expected due to their opportunistic nature, other deep-diving cetaceans, such as Sperm whales (Physeter macrocephalus) and different beaked whale species have more defined routes and areas of preference around the island. Here, the underwater topography plays a more significant role due to the fact that they spend a larger amount of time below the surface at greater depths.

While Sperm whales are usually encountered some miles off the coast, Blainville’s beaked whales (Mesoplodon densirostris) are often sighted in the deeper coastal waters between Calheta and Madalena do Mar. The steeper gradient here means the animals can forage and socialize at depths of around 400-800m and still find refuge in close vicinity to the coastline. Today, however, we had a surprise encounter on our zodiac Stenella during our final tour of the day with this species near Jardim do Mar at an unusually shallow depth of 90m!

Beaked whales of the family Ziphiidae are thought to be suction feeders that mainly feed on deep-sea cephalopods such as squid. In summer, however, squid migrate up to shallower depths more frequently and have also been sighted at the surface during our trips. Moreover, several Mesoplodonspecies such as the Blainville’s beaked whale also enjoy a diet that includes small schooling fish and crustaceans. While foraging advantages may have played a role in this unusual sighting, we still cannot assume to understand the complex reasoning of such intelligent and mysterious toothed whales.

We will just have to accept the fact that predictions of species occurrence in certain areas are often futile and should enjoy the fact that every cetacean encounter is, for the most part, a little surprise.

By Paula Thake

Sightings of the day

Ribeira Brava

10:00 Atlantic spotted dolphins, Bottlenose dolphins

14:30 Bottlenose dolphins

Stenella

09:00 Atlantic spotted dolphins, Bottlenose dolphins

15:30 Bottlenose dolphins, Blainville’s beaked whales