14.08.2020 – Stealth

Our spotter already had a few sightings lined up for us as we exited the marina on board our Stenella. The first cetaceans on our list were a few Atlantic spotted dolphins (Stenella frontalis), travelling outside Calheta. The group must have been a nursery subunit since it contained a number of calves gliding alongside their be-speckled mothers and occasionally inquisitively approaching our boat. Next we moved onto a group of Bottlenose dolphins (Tursiops truncatus) that were discretely travelling east before suddenly launching themselves at a large fish, splashing vigorously at the surface as they trapped their prey to devour it.

All toothed whales (Odontocetes) are predators and are intelligent, which means that that they have a few handy hunting techniques up their sleeve. One of the most important tools granted to these coordinated hunters is their sonar, which was used to detect prey, communicate the hunting plans with the rest of the group and to stun their traget, making them easier to catch. While the sonar serves as an important tool for hunting success, the skills necessary to land a good meal are transmitted by means of social learning.

While dolphins tend to learn hunting techniques frothier peers, Short-finned pilot whales. (Globicephala macrorhynchus) and Sperm whales (Physeter macrocephalus) learn it from their families. In both species calves are raised in matriarchal units, where all females are responsible for the care and education of the calves. This obviously includes using their sonar for detecting their prey in the deep and both these large toothed whales happen to be interested in a particularly difficult prey; squid. Squid are smart, agile creatures that are perfectly adapted to their deep, dark habitat in the abyss but are no matcher the skills of the pilot whales and powerful sonar of the Sperm whale.

Both the pilots and the large Sperm whale bull we encountered today were resting at the surface between their challenging foraging dives in the deep. The bull kept avoiding us with some shallow dives but, after approaching the animal carefully from behind, we managed to have a beautiful sighting, take a fluke photo and even scoop up a skin sample. Us whale-watchers also happen to have some stealthy moves up our sleeves and today they even helped us score some scientific data!

By Paula Thake

Sightings of the day

Stenella

15:00 Atlantic spotted dolphins, Bottlenose dolphins, Short-finned pilot whales, Sperm whale