On the 11th of July, a surprise awaited us in the Strait of Gibraltar. For the first time, we spotted ‘false’ orcas (Pseudorca crassidens, also known as the False killer whale) in the Strait of Gibraltar. We were lucky enough to spot these unusual visitors on two separate trips.

The sightings took place east of Tarifa and were about 3.2 kilometres apart. There were around 100–200 animals, accompanied by approximately 10 calves. What a spectacle it was to watch them hunting tuna with their agile manoeuvres and darting through the water. This species of dolphin generally hunts in highly organised pods, encircling schools of fish to drive them tightly together. Once they have caught a fish, they often share the prey amongst themselves. We recognise this behaviour from Orcas as well.

Why are they actually called False orcas?

According to some sources, the name can be traced back to the British palaeontologist Owen. In 1864, he discovered the bones of a dead animal. He had never seen a living specimen, but noted that the skull and teeth were almost identical to those of real Orcas. Thus, the scientific name was coined and has remained ever since. The teeth are pointed and extremely strong. Compared with other dolphins, they are unusually thick and robust. This is the origin of the ‘crassidens’ in the Latin name, which means ‘thick tooth’.

In reality, their size and appearance are more similar to those of Pilot whales than to Orcas (the False orca is the fourth-largest dolphin in the world, whilst the Pilot whale is the second-largest). Both are dark grey, almost black in colour.

Here are the most striking differences:

SHAPE OF THE HEAD:

False orca: slender and pointed. There is no beak.
Pilot whale: extremely bulky and rounded. Distinctively bulging forehead. It also lacks a beak.

DORSAL FIN:

False orca: medium-sized, sickle-shaped and slender. Positioned exactly in the centre of the body.
Pilot whale: very broad, low and positioned far forward, with a long base.

BODY SHAPE:

False orca: Very slender and streamlined. It is a highly manoeuvrable swimmer.
Pilot whale: Massive, robust and powerfully built.

PECTORAL FINS:

False orca: The pectoral fins have an S-shaped curve at the front edge.
Pilot whale: Very long and narrow (in the long-finned pilot whale, they account for up to one-fifth of the body length). Pointed ‘elbow’ bend.

SWIMMING BEHAVIOUR:

False killer whale: Very fast and extremely agile. Often leaps completely out of the water.
Pilot whale: Rather slow and leisurely swimmers. They often lie on the surface (‘logging’) and, as adults, leap only very rarely.

Who’s swimming there? The great Pilot whale vs. False orca quiz!

Can you identify the two species without making any mistakes? You can test your knowledge with these 10 pictures. The answers are below.

Despite all the excitement surrounding this extraordinary sighting, there is one fly in the ointment: False orcas are normally found in tropical, subtropical and warm-temperate oceans. The reason they have entered the Strait of Gibraltar could be the rise in water temperatures caused by climate change, which is leading to a global shift in the habitats of numerous marine species.

ANSWERS:
Picture 1: Pilot whales - broad dorsal fins
Picture 2: False orcas - narrow dorsal fins
Picture 3: Pilot whales - broad dorsal fins
Picture 4: Pilot whales - round heads with a rounded forehead
Picture 5: False orcas - slender, pointed head
Picture 6: Pilot whales - dorsal fin with a long base
Picture 7: Pilot whales - broad dorsal fin and round head
Picture 8: False orcas - narrow dorsal fins
Picture 9: False orcas - fast swimmers – narrow dorsal fins