Pilot Whales from Tenerife / Perfect Diver Magazine 19 issue

Pilot Whales from Tenerife

Planet earth

Text JAKUB BANASIAK

Photos SERGIO DAVID HERNANDEZ HERRERA

MOST OF US HAVE HEARD OF THE DRAMA OF LONG-FINNED PILOT WHALES BEING KILLED EN MASSE IN THE FAROE ISLANDS. IN "PERFECT DIVER" NO. 18 IN THE ARTICLE BY HANNA MAMZER ENTITLED: "RITUAL SLAUGHTER" WE COULD READ ABOUT THE TRADITION OF HUNTING THESE ANIMALS.

Five thousand km south of the Faroe Islands, off the coast of Tenerife, there is a population of short-finned pilot whales, whose safety and well-being seem to be diametrically superior.

Pilot whales, belonging to the delphinidae, are generally much less known than their cousins – bottlenose, common or spotted dolphins, and finally the largest dolphins – killer whales. Which is a pity, because these massively built cetaceans with bulbous heads and rounded dorsal fins are an extremely interesting species, especially in terms of behaviour and family life.

Unlike their long-finned cousins, the short-finned pilot whales prefer warmer waters. Their main foraging habitat is squid-rich areas. The reservoir in the vicinity of Tenerife and La Gomera in the Canaries provides them with great living conditions.

These animals, sociable and accustomed to the presence of humans, are concentrated here in the strait separating the southern coast of Tenerife from the neighbouring island of La Gomera, and their observation is possible at any time of the year.

Bottlenose dolphin off the coast of Tenerife

These cetaceans are called "pilot whales" in English. This name probably comes from the fact that it was once believed that stocks of these animals were led by pilots. In addition to the rounded head, pilot whales can also be identified by their distinctive back curved, rounded dorsal fin at the front of their body. In males, the base of the dorsal fin is longer and generally larger.

Pilot whale calves have a poorly developed beak and their dorsal fin is more pointed, more upright and more similar in shape to the dorsal fin of smaller dolphins, such as bottlenose dolphins. The latter are also often found southwest of Tenerife.

The body of the pilot whales is black or black-brown, with a large gray saddle behind the dorsal fin. Pilot whales, together with oceanic killer whales, false killer whales and the pygmy killer whales, as well as melon-headed whales, belong to the group of dolphins known as "blackfish".

The short-finned pilot whales feed almost exclusively on squids and octopuses, sometimes only on small shoals (e.g. cod, herring, mackerel). They eat up to 45 kg of food daily.

Females reach sexual maturity at the age of 6–10 years, and males at the age of 12–15 years. Gestation lasts approximately 15 months and occurs every 3 to 5 years. Most births take place in summer. At birth, the calves are approximately 1.8 meters long. The young are fed with their mother's milk for 2 to 4 years.

Thanks to the photo-identification technique of individuals, we know that short-finned pilot whales live in stable social groups and form matrilineal kinship groups. In such groups, all individuals are genetically related to the oldest female, and mating takes place between individuals from different groups.

Between 1991 and 1992, Jim Boran and Sara Heimlich identified 495 shortfinned pilot whales in 46 flocks southwest of Tenerife. Based on the patterns of occurrence, we know that groups that come here for a short time and residents, i.e. groups of permanent residents of this area, appear in this area. Research shows that mating takes place between individuals of different stock. Researchers also found similarities between them and the social structure of the matrilineal stocks of killer whales living here.

On the other hand, research on long-finned grids confirmed that in this species all-parental care ("foster" care for offspring that are not the offspring of the caregivers) is common, and that even more than half of the calves are cared for by non-parents. Both sexes look after the calves and the caretakers and calves can come from different groups. Alloparental care also occurs in short-finned pilot whales, but is less researched. It is believed that among the short-finned pilot whales only females care for their calves.

Research on short-finned whales in Hawaii, USA shows that males have more than one partner – typically there is one sexually mature male in every eight mature females in the group. Males generally leave the family group, while females can stay there for life, attending the calves and youngs. Probably the same pattern is in Tenerife.

The maximum life expectancy is considered to be 45 years for males and an average of 60 years for females.

Calves (less than half the length of adults) usually swim close to the mother, and newborns (with lighter lines visible on the body – a remnant of wrinkles in the prenatal period) do not move away from her at all. At this age, the risk of being attacked by a shark or killer whale is very high.

Usually individual animals in a family group or the whole group dive together. Juveniles often emerge earlier or sometimes remain completely afloat. Often, so-called "preschool groups" can be observed with a few adults and a few young animals – walking together or resting together on the surface of the sea.

Young pilot whale

Jumps above the water are much less frequent in pilot whales than, for example, in the case of bottlenose dolphins living nearby.

Pilot whales are amazing freedivers. They dive at a speed of about 2–5 meters per second to a depth of 500–600 meters. There, they slow down, use echolocation to orientate themselves in the field and start fast hunting at a speed of 25–30 km / h, to an average depth of 700 m.

If we compare this with the diving speeds of other species (2 m/s for sperm whales, 1.5 m/s for beaked whales), it turns out that the pilot whales that we often see lying motionless in the water are not slow or lazy at all. They are downright professionals! During the research conducted by SECAC (Sociedad para el Estudio de los Cetáceos en el Archipiélago Canario), a male was observed, who made 17 consecutive dives at a depth of over 700 m between 9.00 am and 4.00 pm! Even a calf less than a year and a half with a body length of 2.20 m dived 10 times to an average depth of 100 m, also descending on the same day to a depth of 370 m. Research has also shown that night dives are definitely shallower, reaching approx. 100–300 m, because squid at night are active at shallower depths. Short-finned

pilot whales have been nicknamed as the “cheetahs of the deep sea” for their deep, high-speed, sprint-dives to chase and capture large squid.

When we understand how dynamically and deeply pilot whales dive, it is easier to understand their regenerative behaviour on the surface. These dolphins spend long periods of rest, almost like logs on the surface of the water, to prepare and oxygenate before the next great-depth hunt for squid and fish. This makes them easy to observe, as long as we don't bother them.

Pilot whale – spy hopping

In the resting phase, they breathe gently for a few minutes and replenish their oxygen supply. When observing pilot whales, it often seems that the proximity of the boat does not bother them. However, it should be taken into account that animals may be too tired to move away or dive.

It happens that the youngs come to the boat and "play". They show one or both pectoral fins or raise their heads out of the water to peek around. Such "spy hopping" can also be observed in the performance of adult individuals. In some cases, when boats get too close or go too fast, pilot whales begin to move, dive or move away.

When animals rest or sleep on the surface of the water, they usually do not make sounds that could be heard using a hydrophone. But when they "socialise" with each other, dive or hunt, you can hear many different clicks and whistles. Short-finned whales have a wide vocal repertoire, including whistling, chirping, buzzing and other hoarse sounds used in social interactions. Clicks are also used for echolocation.

Herd communication, social life, interpersonal relationships, and perhaps also emotional issues, are very important to pilot whales. Researchers have repeatedly documented how pilot whales mourn the death of a calf. A mother can keep a dead newborn baby with her for many days, not wanting to part with it.

Use the qr code to see this behavior

Similar situations have also been observed in the Strait of Gibraltar. One day a family group headed by a female with a dead calf came to the whale watching boat. She stayed by the boat for several minutes, keeping the little pilot whale's carcass afloat. Perhaps it would be an anthropocentric abuse, but it looked like she was asking people for help, helpless in her pain.

Can these social, intelligent, empathetic, but also powerful animals pose a threat to swimmers or divers? In 2004, Michael Scheer, Bianka Hofmann, Itay P.Behr published the results of their 1996 and 2001 field research on the interaction of short-finned whale with swimmers in the ocean off the southwestern coast of Tenerife. They described the pilot whale behaviour repertoire from 11 interactions with humans, and compared it with previously described pilot whale behaviours reported in the scientific literature. Researchers observed only the affiliate and exploratory behavior of pilot whales, primarily marked by curiosity. These were: repeatedly swimming around a person in the water at a distance of 5–20 m, swimming frontally to the swimmer at a distance of up to 2 m, scanning a person with echolocation and swimming left or right while maintaining eye contact, approaching a person at a distance of less than 2 m, scanning by echolocation in the belly-up position and maintaining stereoscopic eye contact.

The only well-documented case of aggressive behaviour by wild pilot whales towards humans was in 1992 in Kealakakua Bay in Hawaii, when photographer Lee Tepley and his friend Lisa Costello swam very close to a group of pilot whales on a high-speed motorboat. They entered the water with a group of pilot whales about 8 miles offshore. Lisa swam very close to the animals and started petting the curious big male.

Shortly thereafter, Lisa was draggeddown by the same pilot whale and nearlydrowned. The animal grabbed her legseveral times and let her go for a moment,only to pull the woman severalmeters under the water in a moment.Lee Tepley recorded most of the incidentso that the entire incident can beclosely analysed.

Use the qr code to see some footage of this accident

On the other hand, in the study "Delphinids on Display: the Capture, Care, and Exhibition of Cetaceans at Marineland of the Pacific, 1954–1967" describing the situation of cetaceans held in captivity in Marineland, we find numerous references to the threats posed by pilot whales there to aquarium workers. Due to their size and strength, pilot whales have often endangered or harmed divers and their caretakers in the water. This frightened the public and prompted the owners of Marineland to sedate pilot whales with psychotropic drugs. Particularly known for attacks on employees and film crews was the female pilot whale – Bubbles, which led to several serious accidents. Bimbo was also known for his aggressive behaviour. In 1965, local newspapers called the male Bimbo a "psychotic" when a doctor called by Marineland diagnosed the animal with a manic depressive disorder after he had refused to perform for two years, lost weight, had "violent tantrums" and killed several other cetaceans in the reservoir where they lived.

These behaviours prompted Marineland personnel to release the Bimbo back into the ocean in 1967.

Short-finned whales in the wild have virtually no natural enemies, apart from killer whales and a few species of sharks. Scars on the body of adults are usually traces of a fight with giant squid. The relationship between pilot whales and killer whales seems particularly interesting.

In early 2021, scientists listened to 2028 long-finned pilot whales' vocalisations off the coast of Australia. They were surprised to hear 19 instances of vocalisations that resembled the ones produced by killer whales – their rivals. Killer whales compete with pilot whales for food, and are also potential predators of long-finned pilot whales. Pilot whales foraging or eating rests of killer whales' food may go unnoticed if they use killer whales' sounds. It is not yet known whether a similar acoustic mimicry takes place between short-finned pilot whales and killer whales near Tenerife.

The main danger for pilot whales is the contamination of the seas and oceans with toxic chemicals (including heavy metals), which accumulate in their bodies by bioaccumulation and which pass from adipose tissue into breast milk. Such a contaminated milk can be fatal to the calf. Noise pollution is also an issue. Excessive tourist traffic, the noise of boat engines (including whale watching boats), jet skis, fishing boats, ferries, which are numerous in the Canaries, and finally warships with their low frequency sonars make communication difficult and are an additional stressor for dolphins. The greater the stress, the more difficult it is for the whales to recover from exhausting dives, and the less energy they have for essential activities such as caring for offspring, learning to hunt, etc. There is also a greater risk of miscarriage.

Fortunately, pilot whales are not caught in aquariums at present (except for Japan, where pilot whales are still taken to marine parks in Taiji, and where entire family groups are killed). If they live in captivity, it is because they were caught from their natural habitat years earlier or kept in aquariums after rescuing them from sickness or from being stranded on the shore at the beach. It also happens that one of the western aquariums buys a pilot whale from some Japanese marine park.

For pilot whales, being in an aquariumis very burdensome. They are biologicallyadapted to travel long distancesevery day, diving several hundred metersdeep, hunting with the use of echolocation,living in complex family structures.In captivity, they cannot, in anyway, satisfy their locomotor and socialneeds and use the senses of hearing andecholocation. And yet such slavery lastsfor many years. The oldest pilot whaleliving in an aquarium – the female Bubbles– the same female who spent about20 years in Marineland, was held captivein the San Diego SeaWorld artificial reservoirfor another 30 years.

The pilot whale, rescued from beingstuck on a Florida beach in 2011, washeld by SeaWorld in Orlando until hisdeath in 2019 from a bacterial infection.

Short-finned pilot whales have beenkept in captivity at various marine parksin southern California, Hawaii, and Japan,possibly from the late 1940's.Historically, they had low rates of captivesurvival – less than half survived24 months. The fact that dolphinariumsare now able to keep pilot whales alivediametrically longer in captivity doesnot mean that they can provide themwith a long life of well-being, only a longimprisonment.

If you want to meet pilot whales,meet them only in their natural environment.In their world, on their terms.Without causing any distress to wildlifeat sea. Tenerife short-finned pilotwhales are waiting. It is only a 5-hourflight from Poland.

Many thanks to Sergio David Hernandez Herrera fromBONADEA II from Puerto Colon,Tenerife, for the opportunity tolearn more about pilot whalesduring the hours spent togetherat sea and for sharing photosand recording pilot whales.

PERFECTDIVER No. 1(19)/2022 67