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Cetaceans referenced in the Azorean Seas

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CETACEANS REFERENCED IN THE AZOREAN SEAS

Atlantic Spotted Dolphin

(Stenella frontalis)

Adult male Atlantic spotted dolphins can be over 2 meters in length and weigh around 140 kilos. Females are shorter, never more than 2 meters weighing around 130 kg. Newborns measure about 80cm to 120cm in length.

The pigmentation of the Spotted Dolphin can be described as tricolor. The dorsal area is darker, contrasting with shades of light gray on the sides, the caudal peduncle and with a whitish shaded belly. The beak is elongated with a white tip.

The main distinguishing feature of this species is, adults have dark spots on the belly and bright ones on the dorsal and lateral region, whilst the young animals and calves are born without spots and are uniformly grey.

Spotted dolphins are incredibly active. They often follow boats showing off their amazing acrobatic and aerial skills.

They only visit the Azorean waters in summer.

Blainville’s Beaked Whale

(Mesoplodon densirostris)

The adult male is between 4.5m and 6m long and weighs around 800 kilos. Calves measure up to 2.6 meters.

The body of the Blainville’s beaked whale is broad and robust, but it is laterally compressed in the tail region. They have a small flat forehead compared to the beak, which is quite long. In males, the lower jaw presents a large curvature, this being a distinctive feature to recognize this species in the sea; such curvature is milder in females.

As the males reach their sexual maturity, a couple of teeth in the middle of the lower jaw begin to develop. These teeth may exceed the upper jaw and, over time, become encrusted with parasites making them more visible.

They have a blue-grey and black skin color, whilst lighter on the underside.

They are usually very shy and discreet, avoiding most vessels; a major reason for the rare sighting of this species in the Azorean Waters.

Blue Whale

(Balaenoptera musculus)

The blue whale is the largest mammal on the planet. Females reach up to 33.3m in length in the Southern Hemisphere, and 29.8m in the Northern Hemisphere, while adult males generally measure 1.5 m to 3m less.

As for weight, large females can weigh up to 180 tonnes, smaller females and males weigh between 80 tonnes to 150 tonnes.

Newborns measure between 6 meters and 7 meters in length and weigh between 2 tonnes and 4 tonnes.

This massive mammal, has a long streamlined bluish-grey colored body. The dorsal fin is approximately three-quarters of the way along the back of the body.

When emerging to the surface you can see the top of their head and the prominent blowhole. They usually swim alone or at most in pairs.

At sea, the blue whale is fairly identifiable from its very high blow/spout that can reach up to 9 meters to 12 meters. When diving they can show their tail fluke. The blow of a blue whale is one of the best sightings we can get.

In the Azores it is possible to sight blue whales from April to June.

Bottlenose Dolphin

(Tursiops truncatus)

The bottlenose dolphin is one of the most well known species of marine mammals. They have a robust body and a short, thick beak. Their coloration ranges from light gray to black with lighter coloration on the belly.

Inshore and offshore individuals vary in color and size. Inshore animals are smaller and lighter in color, while offshore animals are larger, darker in coloration and have smaller flippers.

Bottlenose dolphins can sometimes be confused with the rough-toothed dolphins, Risso’s dolphins, and Atlantic spotted dolphins in regions of overlapping distributions.

Bottlenose dolphins range in lengths from 1.8 meters to 3.8 meters with males slightly larger than females. Adults weigh from 136 kg to 635 kg).

This is a long-lived dolphin species with a lifespan of 40-45 years for males and more than 50 years for females.

Bottlenose dolphins are commonly found in groups of 2 to 15 individuals. Offshore herds sometimes have several hundred individuals. This species is often associated with pilot whales and other cetacean species.

Like other dolphins, bottlenose dolphins use high frequency echolocation to locate and capture prey.

Bryde’s Whale

(Balaenoptera edeni)

Bryde’s (pronounced “broodus”) whales are members of the baleen whale family and are considered one of the “great whales” or rorquals. These rorquals can reach lengths of about 40-55 ft (13-16.5 m) and weigh up to about 90,000 lbs (40,000 kg). Males are usually slightly smaller than females.

The calves can be up to 3.4m long.

The Bryde’s whale is very similar to the Sei whale. They differ from their three longitudinal ridges on their head and they curve their caudal peduncle when diving.

Very little is known about the social structure of this species, as well as their behavior. However, like other species of baleen whales, this one too travels often alone or in small groups, and sometimes can be found in large groups of animals in the same geographical area, such as in feeding areas as in breeding areas.

Bryde’s whales occur in tropical waters, up to 40° N/S, and are therefore rarely sighted in the Azores.

Common Dolphin

(Delphinus delphis)

The adult male Common Dolphins (delphinus delphis) measure around 2.5 meters and weigh between 100 kg and 200 kg.  The calves measure about 80cm to 90cm.

These animals have an elegant shaped body with a thin beak. The back is dark and the belly is white colored. On each body sides, under the dorsal fin, there is a yellowish bordered and dark “V” on each side.

Common dolphins can live in aggregations of hundreds or even thousands. They sometimes associate with other dolphin species, such as pilot whales. They have also been observed bow riding on baleen whales, and they also to bow ride with boats.

They are fast swimmers (up to 60 km/h), and breaching behavior and aerial acrobatics are very common. They are also known to display altruistic behaviors to support injured members.

Common dolphins can be sighted all year round on the south side of Pico Island.

Cuvier’s Beaked Whale

(Ziphius cavirostris)

Cuvier’s beaked whale or the goose-beaked whale (Ziphius cavirostris), the only member of the genus Ziphius, is the most widely distributed of all the beaked whales. Though it is pelagic, prefers water deeper than 1,000 m (3,300 ft) and avoids ships, it is still one of the most frequently spotted beaked whales.

Adult males reach between 4m and 7m in length and weigh between 2 tones and 3.5 tonnes. Females are slightly larger. Newborns measure between 2 meters and 2.7 meters in length and weigh up to 300 kilogrammes.

Cuvier’s beaked whale’s pigmentation brightens with age, at a younger age they are grey and change to a light brown colour, sometimes under the sunlight they appear almost red.  Due to fighting with other cetaceans these beaked whales normally show a large number of white scars.

At sea, they are easily identified by their heads, which are lighter colored than the rest of the body, with a small indentation behind the blowhole, which ends into a short beak.

They very rarely to travel in large groups, sometimes they even travel alone.

Cuvier’s beaked whales are not very curious animals; this might be one of the reasons why they normally don’t approach boats.

Dwarf Sperm Whale

(Kogia simus)

The dwarf sperm whale is the smallest species commonly known as a whale. It grows up to 2.7 m (8.9 ft) in length and 250 kilograms (550 lb) in weight – making it smaller than the bigger dolphins. The species makes slow, deliberate movements with little splash or blow and usually lies motionless when at the sea’s surface. Consequently it is usually observed only in very calm seas.

The dwarf sperm whale is similar in appearance and behavior to its cousin the pygmy sperm whale. Identification may be close to impossible at sea – however, the dwarf is slightly smaller and has a larger dorsal fin. The body is mainly bluish gray with a lighter underside with slightly yellow vein-like streaks possibly visible. There is a white false gill behind each eye. The flippers are very short and broad. The top of the snout overhangs the lower jaw, which is small. Dwarfs have long, curved and sharp teeth (0–6 in the upper jaw, between 14 and 26 in the lower).

Like other sperm whales, the dwarf sperm whale has a spermaceti organ in its forehead. Like the pygmy, the dwarf is able to expel a dark reddish substance when frightened or attacked—possibly to put off any predators.

Dwarf sperm whales are usually solitary but have occasionally been seen in small groups.

The brain of the dwarf sperm whale is roughly half a kilogram in mass.

False Killer Whale

(Pseudorca crassidens)

The false killer whale is the third-largest member of the oceanic dolphin family (Delphinidae). It lives in temperate and tropical waters throughout the world. As its name implies, the false killer whale shares characteristics, such as appearance, with the more widely known killer whale. Like the killer whale, the false killer whale attacks and kills other cetaceans, but the two species do not belong to the same genus.

The adult male False killer whale measures between 5 meters and 6 meters in length and can weigh over 2 tonnes. Females are slightly smaller measuring between 4m and 5m in length and weighing just over than 1 tonne. Newborns measure about 1.6m length and weigh up to 80kg.

It has a long, streamlined uniformly dark grey to black colored body. The head is narrow and beakless. The dorsal fin is tall and either pointed or rounded and positioned in the middle of the back.

False killer whales are very active, curious and fast swimmers, therefore they bow-ride and wake-ride with the boat.

The false killer whale is a gregarious species, often traveling in groups of several dozen animals, where, apparently, there is no social segregation, these groups can be formed by animals of all ages and both sexes. In the Azores, this species usually appears associated with the migration of tuna, the main food of this cetacean.

Fin Whale

(Balaenoptera physalus)

The fin whale, also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second largest animal after the blue whale, growing to 27.3 metres (89.5 ft) long and weighing nearly 74 tonnes. The newborns measure 6 to 7m and weigh about 2t.

They are large, long and streamlined with grey dark bluish skin on the upper side and on the flippers, and light colored on the downside. It isn’t possible to observe the blowhole and the fin simultaneously on surface. They don’t show their fluke when they dive, but curve their tail peduncle.

At sea, they are fairly identifiable from their asymmetrical pigmentation on their heads. On their right sides their lower jaws are white, whilst the left side is dark as the rest of the body.

They are usually sighted traveling alone, in pairs or in groups 3-7 individuals.

In the Azores, they can be sighted in the months from April to June.

The American naturalist Roy Chapman Andrews called the fin whale “the greyhound of the sea… for its beautiful, slender body is built like a racing yacht and the animal can surpass the speed of the fastest ocean steamship.”

Fraser’s Dolphin

(Lagenodelphis hosei)

Fraser’s dolphins are about 1 meter (3 ft 3 in) long and 20 kg (44 lb) weight at birth, growing to 2.75 m (9 ft 0 in) and 200 kg (440 lb) at adulthood.

They have a stocky build, a small fin in relation to the size of the body, conspicuously small flippers. The dorsal fin and beak are also insubstantial. The upper side is a gray-blue to gray-brown. A dirty cream colored line runs along the flanks from the beak, above the eye, to the anus. There is a dark stripe under this line. The belly and throat are usually white, sometimes tinged pink. The lack of a prominent beak is a distinguishing characteristic of the dolphin. From a distance however it may be confused with the striped dolphin which has a similar coloration and is found in the same regions.

Fraser’s dolphins swim quickly in large tightly packed groups of about 100 to 1000 in number. Often porpoising, the group chop up the water tremendously. The sight of seeing a large group fleeing from a fishing vessels has been reported as “very dramatic”.

It is also marked by having the smallest genitalia of any open sea dolphin.

The species feeds on pelagic fish, squid and shrimp found some distance below the surface of the water (200 m/660 ft to 500 m/1,600 ft). Virtually no sunlight penetrates this depth, so feeding is carried out using echolocation alone.

Gervais Beaked Whale

(Mesoplodon europaeus)

Gervais’ beaked whale, sometimes known as the Antillian beaked whale, Gulf Stream beaked whale, or European beaked whale (from which its scientific name is derived) is the most frequently stranding type of mesoplodont whale off the coast of North America.

This species is the largest of the mesoplodonts and rather gracile, elongated, and laterally compressed compared with the others. The mouth line is remarkably straight, even in males, and the two teeth of the male erupt towards the tip of the beak, and are hardly noticeable. The head is overall small and tapering in outline. The melon only bulges very slightly.

The coloration is dark gray on top and lighter gray on bottom. Females sometimes have lighter spots near the genitals and face, with a dark circle remaining around the eyes. Juveniles start off with a lighter coloration, but soon darken.

Males are 4.5 meters (15 ft) in  length and females are at least 5.2 meters (17 ft) and probably weigh more than 1200 kg (2600 pounds). Calves are believed to be 2.1 meters (7 feet) in length.

The species is believed to be naturally rare, and no estimates have been attempted

Traveling in groups or in pairs, the Gervais’ beaked whale is a shy and a difficult species to observe.

Humpback Whale

(Megaptera novaeangliae)

The humpback whale is a species of baleen whale. One of the larger rorqual species, adults range in length from 12–16 metres (39–52 ft) and weigh approximately 36,000 kilograms (79,000 lb). The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal known for breaching and slapping the water with its tail and pectorals.

Newborn calves are roughly the length of their mother’s head. At birth, calves measure 6 metres (20 ft) at 1.8 tonnes. The mother, by comparison, is about 15 metres (49 ft). They nurse for approximately six months, then mix nursing and independent feeding for possibly six months more. Humpback milk is 50% fat and pink in color.

Males produce a complex song lasting 10 to 20 minutes, which they repeat for hours at a time. Its purpose is not clear, though it is thought that it may have a role in mating.

Like other large whales, the humpback was and is a target for the whaling industry. Once hunted to the brink of extinction, its population fell by an estimated 90% before a moratorium was introduced in 1966. While stocks have since partially recovered, entanglement in fishing gear, collisions with ships, and noise pollution continue to impact the 80,000 humpbacks worldwide.

In the Azores, Humpback whales are sighted in small groups, sometimes very near the shore.

Long-finned Pilot Whale

(Globicephala melas)

The long-finned pilot whale is the second largest species of oceanic dolphin. It shares the genus Globicephala with the short-finned pilot whale (Globicephala macrorhynchus). Long-finned pilot whales are known as such because of their unusually long pectoral fins. The long-finned pilot whale has more neocortical neurons than any mammal studied to date, including humans.

The long-finned pilot whale is one of the largest species of dolphin. The sexes are dimorphic, with females reaching lengths of up to 5.8 meters and 1800 kg (1.8 tonnes), while males are significantly larger at up to 7.6 meters and 3500kg (3.5 tonnes). Newborn calves are generally 1.8 m (5 ft 11 in) at birth, and weigh about 102 kg (225 lb).

These groups have been observed socializing with Common bottlenose dolphins, Atlantic white-sided dolphins and Risso’s dolphins. Pilot whales mainly feed on cephalopods, though in certain regions fish may be more prominent in their diet. Northwestern Atlantic whales are thought to dine predominantly on short-finned squid.

One of the reasons why they are rarely sighted in the Azores is this species (Globicephala melas) prefers colder waters unlike the short-finned pilot whale (Globicephala macrorhynchus); their distribution is known to occur primarily from 40 ° N and 47 ° S.

They are very active and often curious, approaching vessels in groups of 10 to 30 individuals.

Minke Whale

(Balaenoptera acutorostrata)

The minke whales are the second smallest baleen whale; only the pygmy right whale is smaller. Upon reaching sexual maturity (6–8 years of age), males measure an average of 6.9 m (23 ft) and females 8 m (26 ft) in length, respectively. Both sexes typically weigh 4–5 tonnes at sexual maturity, and the maximum weight may be as much as 10 tonnes. Newborn calves measure 2.4 to 2.8 m (7.9 to 9.2 ft) at birth. The newborns nurse for five to 10 months. Breeding peaks during the summer months. Calving is thought to occur every two years.

The minke whale is a black/gray/purple color. Common minke whales (Northern Hemisphere variety) are distinguished from other whales by a white band on each flipper. The body is usually black or dark-gray above and white underneath. Minke whales have between 240 and 360 baleen plates on each side of their mouths. Most of the length of the back, including dorsal fin and blowholes, appears at once when the whale surfaces to breathe.

Minke whales typically live for 30–50 years; in some cases they may live for up to 60 years.

The brains of minke whales have around 12.8 billion neocortical neurons and 98.2 billion neocortical glia.

The whale breathes three to five times at short intervals before ‘deep-diving’ for two to 20 minutes. Deep dives are preceded by a pronounced arching of the back. The maximum swimming speed of minkes has been estimated at 38 km/h (24 mph).

North Atlantic Right Whale

(Eubalaena glacialis)

The North Atlantic right whale, which means “good, or true, whale of the ice”), is a baleen whale, one of three right whale species belonging to the genus Eubalaena, all of which were formerly classified as a single species. Because of their docile nature, their slow surface-skimming feeding behaviors, their tendencies to stay close to the coast, and their high blubber content (which makes them float when they are killed, and which produced high yields of whale oil), right whales were once a preferred target for whalers, who reportedly considered them the “right” whales to hunt.

The adult male North Atlantic whale (Eubalaena glacialis) is about 15m long, whilst females are slightly larger than the males. Their average weight is of 70t. Calves are 13–15 feet (4.0–4.6 m) long at birth and weigh approximately 3000 pounds (1400 kg).

At present, they are among the most endangered whales in the world, and they are protected under the U.S. Endangered Species Act and the Marine Mammal Protection Act. There are about 400 individuals in existence in the western North Atlantic Ocean – they migrate between feeding grounds in the Gulf of Maine and their winter calving areas off Georgia and Florida, an ocean area with heavy shipping traffic. In the eastern North Atlantic, on the other hand – with a total population reaching into the low teens at best – scientists believe that they may already be functionally extinct. Vessel strikes and entanglement in fixed fishing gear, which together account for nearly half of all North Atlantic right whale mortality since 1970, are their two greatest threats to recovery.

Northern Bottlenose Whale

(Hyperoodon ampullatus)

The northern bottlenose whale is a species of bottlenose whale in the ziphiid family, and being one of two members of the genus Hyperoodon. It is one of the deepest diving mammals known, reaching depths of 1453 m (4767 ft).

The species is fairly rotund and measure 9.8 metres (32 ft) in length when physically mature, and there have been claims that large individuals reach up to 11.2 metres (37 ft), rivaling Giant Beaked Whales and being significantly larger than known records of the subspecies in southern hemisphere and the close-resembling tropical species. The beak is long and white on males but grey on females. The dorsal fin is relatively small at 30–38 centimetres (12–15 in) and set far back on their bodies. It is falcate (sickle-shaped) and usually pointed. The back is mid-to-dark grey. They have a lighter underside.

Weight estimates are hard to come by. For the northern bottlenose whale, 5,800–7,500 kilograms (12,800–16,500 lb) is given somewhat consistently.

Newborn calves measure 3,5m of length and 300 kg of weight.

Despite being deep diving beaked whales, they are known to come, play, and rest in shallow waters in small numbers at each time. They are also very playful and curious towards human vessels unlike most of other beaked whales, this was one of factors in making them as an easy target for whalers.

According to the sightings of Aqua Açores, the northern bottlenose whales are seen from July to August

Orca “Killer Whale”

(Orcinus orca)

The killer whale, also referred to as the orca whale or orca, and less commonly as the blackfish or grampus, is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas. Killer whales as a species have a diverse diet, although individual populations often specialize in particular types of prey. Some feed exclusively on fish, while others hunt marine mammals like pinnipeds, and even large whales. They have been known to drown baleen whale calves to eat their fins. Killer whales are regarded as apex predators, lacking natural predators.

Killer whales are highly social; some populations are composed of matrilineal family groups which are the most stable of any animal species. Their sophisticated hunting techniques and vocal behaviors, which are often specific to a particular group and passed across generations, have been described as manifestations of culture.

Males typically range from 7 to 9 metres (23 to 30 ft) long and weigh in excess of 6 tonnes. Females are smaller, generally ranging from 6 to 8 m (20 to 26 ft) and weighing about 3 to 4 tonnes. The largest male killer whale on record was 9.8 m (32 ft), weighing over 10 tonnes, while the largest female was 8.5 m (28 ft), weighing 7.5 tonnes. Calves at birth weigh about 180 kg (400 lb) and are about 2.4 m (7.9 ft) long.

In the Azores, in the central group of islands sightings are uncommon. However, Aqua Azores records, almost every year, the passing of killer whales on the southern side of the island of Pico. These sightings are transient orcas, with small groups.

Pygmy Sperm Whale

(Kogia breviceps)

The pygmy sperm whale is not much larger than most dolphins. They are about 1.2 metres (3 ft 11 in) at birth, growing to about 3.5 metres (11 ft) at maturity. Adults weigh about 400 kilograms (880 lb). Newborn calves are about 1.2 metres (3 ft 11 in) in length, and are weaned at around one year of age.

The underside is a creamy, occasionally pinkish, colour and the back and sides are a bluish grey; there is, however, considerable intermixing between the two colours. The shark-like head is large in comparison to body size, given an almost swollen appearance when viewed from the side. There is a whitish marking, often described as a “false gill”, behind each eye.

The lower jaw is very small and slung low. The blowhole is displaced slightly to the left when viewed from above facing forward. The dorsal fin is very small and hooked; its size is considerably smaller than that of the dwarf sperm whale and may be used for diagnostic purposes.

This whale makes very inconspicuous movements. It rises to the surface slowly, with little splash or blow, and will remain there motionless for some time. In Japan the whale was historically known as the “floating whale” because of this. Its dive is equally lacking in grand flourish – it simply drops out of view. The species has a tendency to back away from rather than approach boats. Breaching has been observed, but is not common.

Pygmy sperm whales are normally either solitary, or found in pairs but have been seen in groups of up to six. Dives have been estimated to last an average of eleven minutes, although longer dives of up to 45 minutes have been reported.

Sightings in the Azores have always been of solitary whales.

Risso’s Dolphin

(Grampus griseus)

Risso’s dolphin is named after Antoine Risso, whose description formed the basis of the first public description of the animal, by Georges Cuvier, in 1812. Another common name for the Risso’s dolphin is grampus (also the species’ genus).

Risso’s dolphin has a relatively large anterior body and dorsal fin, while the posterior tapers to a relatively narrow tail. The bulbous head has a vertical crease in front.[4]

Infants are dorsally grey to brown and ventrally cream-colored, with a white anchor-shaped area between the pectorals and around the mouth. In older calves, the nonwhite areas darken to nearly black, and then lighten (except for the always dark dorsal fin). Linear scars mostly from social interaction eventually cover the bulk of the body. Older individuals appear mostly white. Most individuals have two to seven pairs of teeth, all in the lower jaw.

Length is typically 3 meters (10 feet). Like most dolphins, males are typically slightly larger than females. This species weighs 300–500 kilograms (660–1,100 lb), making it the largest species called “dolphin”.

Risso’s dolphins are easy identifiable at sea due to their round blunt head with bulging forehead that slopes steeply to the mouth. The dorsal fin is tall, pointed and darkened. Risso’s dolphins are more robust than most dolphins.

Although being a shyer and less acrobatic comparing to the other species, they frequently allow boats to approach.

Risso’s dolphins are a resident species in the Azores and therefore they can be easily found all year long in the bays on the south side of Pico.

Rough Toothed Dolphin

(Steno bredanensis)

The Rough-toothed Dolphin (Steno bredanensis) is a species of dolphin that can be found in deep warm and tropical waters around the world.

The species was first described by Georges Cuvier in 1823. The genus name Steno, of which this species is the only member, comes from the Greek for ‘narrow’, referring to the animal’s beak — which is a diagnostic characteristic of the species.

The rough-toothed dolphin is a relatively large species, with adults ranging from 2.09 to 2.83 metres (6.9 to 9.3 ft) in length, and weighing between 90 and 155 kilograms (198 and 342 lb); males are larger than females. The calves are about 100 centimetres (39 in) long at birth, and grow rapidly for the first five years of life

Its most visible characteristic feature is its conical head and slender nose; other dolphins either have a shorter snout or a more visibly bulging melon on the forehead. As the common name for the species implies, the teeth are also distinctive, having a roughened surface formed by numerous narrow irregular ridges. They have been reported to have between nineteen and twenty-eight teeth in each quarter of the jaw.

The flippers are set back further along the body than in other similar dolphins, although, at sea this dolphin may be confused with spinner, spotted and bottlenose dolphins. The dorsal fin is pronounced, being from 18 to 28 centimetres (7.1 to 11.0 in) in height. The animal’s flanks are a light gray, while the back and dorsal fin are a much darker gray. Older individuals often have distinctive pinkish, yellow, or white markings around the mouth and along the underside.

This species favours deep warm and tropical waters therefore they are rarely sighted in the Azores.

Sei Whale

(Balaenoptera borealis)

The sei whale, is a baleen whale, the fourth-largest rorqual after the blue whale, the fin whale and the humpback whale. It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids polar and tropical waters and semi-enclosed bodies of water. The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical waters.

Reaching 19.5 metres (64 ft) long and weighing as much as 28 tonnes, the sei whale daily consumes an average of 900 kilograms (2,000 lb) of food, primarily copepods, krill, and other zooplankton. Newborn calves measure 4.5 meters to 5 meters in length and weigh around 1 tonne.

It is among the fastest of all cetaceans, and can reach speeds of up to 50 kilometres per hour (31 mph) (27 knots) over short distances.

Sei whales usually travel alone or in pods of up to six individuals. Larger groups may assemble at particularly abundant feeding grounds.

Very little is known about their social structure.

Sei whales live in all oceans, although rarely in polar or tropical waters. The difficulty of distinguishing them at sea from their close relatives, Bryde’s whales and in some cases from fin whales, creates confusion about their range and population, especially in warmer waters where Bryde’s whales are most common.

In Azores, during the spring and summer months you can find this species feeding on shoals of small fish, along with dolphins.

Short-finned Pilot Whale

(Globicephala macrorhynchus)

The short-finned pilot whale is one of the two species of cetaceans in the genus Globicephala. It is part of the oceanic dolphin family (Delphinidae), though its behaviour is closer to that of the larger whales.

Short-finned pilot whales can be confused with their relatives the long-finned pilot whales, but there are various differences. As their name indicate, their flippers are shorter than those of the long-finned pilot whale, with a gentler curve on the edge. They have fewer teeth than the long-finned pilot whale, with 14 to 18 on each jaw. Short-finned pilot whales are black or dark grey with a grey or white cape. They have grey or almost white patches on their bellies and throats and a grey or white stripe which goes diagonally upwards from behind each eye.

Their heads are bulbous and this can become more defined in older males. Their dorsal fins vary in shape depending on how old the whale is and whether it is male or female. They have flukes with sharply pointed tips, a distinct notch in the middle and concave edges. They tend to be quite slender when they are young, becoming more stocky as they get older.

Adult males are about 5.5 meters in length, whereas adult females only reach about 3.7 meters in length. Adults weigh from 2200 to 6600 pounds (1,000-3,000 kg). Newborn short-finned pilot whales are about 1.4 meters – 1.9 meters long and weigh about 60 kg (130 lb). Males live nearly 45 years, whereas females can live up to 60 years.

In the Azores, pilot whales are often seen in small groups to dozens of individuals, or alone in mixed groups of bottlenose dolphins.

Sowerby’s Beaked Whale

(Mesoplodon bidens)

Sowerby’s beaked whale, also known as the North Atlantic or North Sea beaked whale, is a species of toothed whale.

Sowerby’s beaked whale has a typical body shape for the genus, and is mainly distinguished by the male’s dual teeth positioned far back in the mouth. The whale’s beak is moderately long, and the melon is slightly convex. The colouration pattern is a grey with light countershading on the bottom, and frequently has cookie cutter shark bites and scars from teeth (in males).

The whale reaches 5 metres (16 ft) in females and 5.5 metres (18 ft) in males, with a weight of 1000-1300 kilograms (2200-2900 lb). The gestation period lasts for 12 months and the young are born at a length of 2.4 to 2.7 metres (8 to 9 ft) with a weight of around 185 kilograms (400 lb).

Sowerby’s beaked whales are reclusive creatures that stay away from ships and are rarely sighted. The whales are occasionally in groups of 8 to 10 individuals (males, females, and calves) and have been known to strand in groups as well. They are believed to primarily feed on squid and molluscs, but cod has also been found in their stomachs. They have been known to dive down at times approaching 30 minutes.

Sowerby’s beaked whale ranges from Nantucket to Labrador in the western North Atlantic and from Madeira to the Norwegian Sea in the eastern North Atlantic.

In the Azores, the Sowerby’s beaked whales have been sighted in small groups of 8, even some calves have been sighted.

Sperm Whale

(Physeter macrocephalus)

The sperm whale, or cachalot, is the largest of the toothed whales and the largest toothed predator. It is the only living member of genus Physeter, and one of three extant species in the sperm whale family, along with the pygmy sperm whale and dwarf sperm whale of the genus Kogia.

Mature males average at 16 metres (52 ft) in length but some may reach 20.5 metres (67 ft), with the head representing up to one-third of its length. The sperm whale feeds primarily on squid. Plunging to 2,250 metres (7,382 ft) for prey, it is the second deepest diving mammal, following only the Cuvier’s beaked whale. The sperm whale’s clicking vocalization, a form of echolocation and communication, may be as loud as 230 decibels, making it the loudest sound produced by any animal. It has the largest brain of any animal on Earth, more than five times heavier than a human’s. Sperm whales can live for more than 60 years.

The sperm whale’s flukes (tail lobes) are triangular and very thick. Proportionally, they are larger than that of any other cetacean, and are very flexible. The whale lifts its flukes high out of the water as it begins a feeding dive. It has a series of ridges on the back’s caudal third instead of a dorsal fin. The largest ridge was called the ‘hump’ by whalers, and can be mistaken for a dorsal fin because of its shape and size.

In contrast to the smooth skin of most large whales, the skin on the back is usually wrinkly and has been likened to a prune by whale-watching enthusiasts. Albinos have been reported

The sperm whale can be found anywhere in the open ocean. Females and young males live together in groups while mature males live solitary lives outside of the mating season. The females cooperate to protect and nurse their young. Females give birth every four to twenty years, and care for the calves for more than a decade. A mature sperm whale has few natural predators. Calves and weakened adults are taken by pods of orcas.

Striped Dolphin

(Stenella coeruleoalba)

The striped dolphin is found in temperate and tropical waters of all the world’s oceans. It is a member of the oceanic dolphin family, Delphinidae.

It has a similar size and shape to several other dolphins that inhabit the waters it does. However, its colouring is very different and makes it relatively easy to spot at sea. The underside is blue, white, or pink. One or two black bands circle the eyes, and then run across the back, to the flipper. These bands widen to the width of the flipper which are the same size. Two further black stripes run from behind the ear – one is short and ends just above the flipper. The other is longer and thickens along the flanks until it curves down under the belly just prior to the tail stock. Above these stripes, the dolphin’s flanks are coloured light blue or grey. All appendages are black.

At birth, calves weigh about 10kg (22 lb) and are up to a meter (3 feet) long. By adulthood, females grow to 2.4 m (8 ft) weighing 150 kg (330 lb) and males to 2.6 m (8.5 ft) weighing around 160 kg (352 lb).

In common with other dolphins in its genus, the Striped Dolphin moves in large groups, usually up to thousands of individuals in number. Groups may be smaller in the Mediterranean and Atlantic. They also mix with common dolphins.

The striped dolphin is as capable as any dolphin at performing acrobatics, frequently breaching and jumping far above the surface of the water. Sometimes, they approaches boats in the Atlantic and Mediterranean, but this is less common in other areas, where they have been heavily exploited in the past.

In the Azores, Striped dolphins are frequently sighted in small social groups, they have been occasionally sighted in larger social groups.

True’s Beaked Whale

(Mesoplodon mirus)

True’s beaked whale is a medium-sized whale in the mesoplodont genus. The common name is in reference to Frederick W. True, a curator at the United States National Museum (now the Smithsonian). There are two distinct populations in the Atlantic and Indian Oceans (this species is absent in the tropics) which may be separate subspecies.

This whale has a normal mesoplodont body, except that it is rotund in the middle and tapering towards the ends. The two distinctive teeth on the males are small and set on the very end of the beak. The melon is rather bulbous, and leads into a short beak. There is a crease behind the blowhole, and a sharp dorsal ridge on the back near the dorsal fin. The coloration is gray to brownish gray on the back which is lighter below, and notably darker on the “lips”, around the eye, and near the dorsal fin. There is sometimes a dark blaze between the head and dorsal fin as well.

One female in the Southern Hemisphere was bluish black with a white area between the dorsal fin and tail as well as a light gray jaw and throat, as well as black speckling. Scars from fighting and cookiecutter sharks are present on males.

True’s beaked whale reaches around 5.3 metres (17 ft) with the females weighing 1,400 kilograms (3,100 lb) and the males weighing 1,010 kilograms (2,230 lb). Newborn calves are around 2.3 metres (7.2 ft) long and weigh about 136kg.

True’s beaked whales are shy towards vessels, which makes the sightings in the Azores very rare.

2 COMMENTS

  1. […] Whether you are a complete beginner looking to take your PADI, an enthusiast or an experienced diver looking to photograph marine wildlife, you must put the Islands of the Azores on the very top of your list.  Diving in the Azores is a lifetime experience that you will never forget.  Imagine this;  there are 27 species of Cetaceans referenced in the Azorean Seas. […]

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