11.09.2018 – Off the beaten track

This morning we searched far and wide for Atlantic spotted dolphins (Stenella frontalis) to snorkel with and found a small school of curious Bottlenose dolphins (Tursiops truncatus) instead. On our way back to the marina, both spotter and skipper saw a beaked whale surface for a short period before it sadly disappeared. Unfortunately, our crew on board was not able to relocate the animal to identify the species. During the afternoon tours, guests on both boats were able to enjoy sightings involving Bottlenose dolphins and the impressive and rarely sighted Cuvier’ beaked whales (Ziphius cavirostris).

Beaked whales are probably the most difficult group of cetaceans to approach during a whale watching tour and the most poorly documented group of cetaceans. Taxonomically, all 23 beaked whale species are summarized within the family of the Ziphiidae, which encompasses a diverse variety of these deep-diving cetaceans. Beaked whales spend the majority of their time in the remote, deep, dark ocean where they hunt and socialize. Like all toothed whales they rely on their bioacoustics for orientation, communication and for foraging making them particularly sensitive to noise at the surface, often leading to very evasive behaviour of the animals towrds boats.

Currently four species of beaked whales have been confirmed to visit the Madeiran archipelago: the Blainville’s beaked whale (Mesoplodon densirostris), the Cuvier’s beaked whale, the Northern Bottlenose whale (Hyperoodon ampullatus) and the Sowerby’s beaked whale (Mesoplodon bidens). Blainvilles are sighted quite frequently around Madeira and have been closely monitored by local researchers, whose studies have shown  a site fidelity to the islands waters amongst several groups. Cuvier sightings, on the other hand, are more rare around Madeira whilst sightings involving the latter two species are extremely scarce.

The Cuvier and the Blainville’s beaked whales are easy to identify during a sighting but other species of beaked whales certainly aren’t, particularly those belonging to the genus Mesoplodon. In fact, the existence of some species of the genus is only known through the analysis of skeletal material or stranded carcasses. The external appearance of several species is therefore extremely poorly documented often making it impossible to identify them out at sea. Moreover, their shy nature makes it difficult to photograph characteristic features that have been concluded to distinguish the species from the available material of deceased individuals such as the shape of the melon or the position of their teeth. There are very few confirmed sightings, for instance, of the True’s beaked whale (Mesoplodon mirus) and the species has only been photographed alive a handful of times.

The fact that Madeira is situated far off the mainland in the East Atlantic, so rather off the beaten track, makes the occurrence of a variety of species possible. For now 26 species of cetaceans have been confirmed to visit the waters surrounding Madeira but this remote oceanic habitat may also reveal other visitors in the near future, including some other mysterious beaked whale species. So when a beaked whale surfaces, although we assume it may be a Blainville, you can never be too sure and can anticipate the possible event of a new species breaking the deep, blue surface around the archipelago.

By Paula Thake

Sightings of the day

Ribeira Brava

13:30 Bottlenose dolphins, Cuvier’s beaked whales

Stenella

09:00 Bottlenose dolphins, Beaked whale

15:30 Bottlenose dolphins, Cuvier’s beaked whales