Sightings Summary April 2017

The month of April was also great in terms of sightings. The weather conditions were a bit unstable as it is usual for spring time in the Azores, so we had to cancel few tours. Nevertheless, when sea state conditions allowed to go out at sea we had the chance to observe a total of 12 species of cetaceans and one species of turtle, the loggerhead.


Resident species:

Common dolphin

Risso’s dolphin

Bottlenose dolphin

Sperm whale (sighted once)


Migratory species:

Blue whale

Sei whale

Fin whale

Humpback whale

Striped dolphin


Undefined patterns:

Beaked whale (sighted once). Information of their residency patterns are not available for the Azores, although some species may stay year-round


Occasional visitors:

False killer whale



The pod of orcas observed on the last day of the month included three adult males recognizable for their tall and straight dorsal fins.

Did you know that male orcas have the tallest dorsal fin among cetaceans and that it can reach almost 2 meters in height? Females and juveniles have a smaller sickle-shaped dorsal fin.

The dorsal fin is made of connective tissue, so there are no bones in it. It is used to enhance maneuverability and stabilize the body. It has also a thermo-regulation function.

The collapse of the dorsal fin on one side is rare in the wild, but frequent in captivity. This is due to the circling swimming patterns orcas are subject to, when kept in a confined tank. The pressure of the flowing water is not equally distributed to both sides of the fin. Also, dehydration due to a poorer diet may lead to a shrinking of the tissues and hence to a higher probability of dorsal fin bending.

There exist different ecotypes of orcas: some populations feed exclusively on fish, others on marine mammals and others are opportunistic, meaning they can adjust their diet depending on the resources that are most available.

orcas are definitely among the most charismatic cetaceans and their occasional occurrence in the Azores waters makes them even more fascinating.

Hopefully, we will be able to observe them soon again 🙂





Arianna Cecchetti

About Arianna Cecchetti

Arianna is a Marine Biologist and was Main Guide at TERRA AZUL since 2009, and Technical & Scientific Director until 2018. Originally from Italy, she sees herself more as a world citizen. Arianna deserves the very best, and we hope she can come back to share her passion for the sea with us again.

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