Stenella longirostris

Stenella longirostris

Spinner dolphin

The Spinner Dolphin (Stenella Stenella longirostris, Spinner dolphinlongirostris) is a small dolphin found in off-shore tropical waters around the world. It is famous for its acrobatic displays in which they will spin longitudinally along their axis as they leap through the air.

Taxonomy

The Spinner Dolphin is sometimes referred to as the Long-snouted Dolphin, particularly in older texts, to distinguish it from the similar Clymene Dolphin which is often called the Short-snouted Spinner Dolphin. The species was discovered by John Gray in 1828. There are four named subspecies:

* Eastern Spinner Dolphin (S. l. orientalis), found in the tropical eastern Pacific.
* Central American or Costa Rican Spinner Dolphin (S. l. centroamericana), also found in the tropical eastern Pacific.
* Gray’s or Hawaiian Spinner Dolphin (S. l. longirostris), found in the central Pacific around Hawaii but represents a mixed bag of broadly similar subtypes found throughout the world.
* Dwarf Spinner Dolphin (S. l. roseiventris), first found in the Gulf of Thailand.

However the species display a greater variety than these subspecies might indicate. A hybrid form characterized by its white belly is noted in the eastern Pacific. Other less distinct groupings have been identified in other oceans.

The specific name comes from the Latin term for long-beaked.

This is the most acrobatic dolphin. They jump high out of the water and spin around like a spinning top. They live in the open ocean and eat mostly fish.

The male Spinner Dolphin is known to spin when leaping up from the water because they “put on a show” for female dolphins, and that’s why they are called the “Spinner” Dolphin.
Physical description

The Spinner Dolphin is usually dark gray, with darker patches in the tail stock, back and throat. Usually it has creamy-white patch on the belly though this varies considerably. Their beaks are distinctively long and thin, and with a dark tip. The fins, also, are lengthy for dolphins of this size. The dorsal fin is erect and even leans forward in older males found in the Eastern Pacific Ocean. However this description has to be described as a little loose – Spinner Dolphins are the most variable in form of all cetaceans.

Adults have varied in size from 129 cm to 235 cm and weight from 23 kg to 78 kg. The gestation period is about 10 months. Individuals reach maturity at four to seven years (females) and seven to ten years (males). Their longevity is unknown.

Spinner Dolphins congregate in groups that vary from just a few dolphins to great numbers up in the thousands. They are consistently acrobatic and keen bow-riders. The reason for the animal’s spinning is said to be unknown by some people, but other people say that male Spinner Dolphins are trying to attract the females. Another suggestion is that the great cauldron of bubbles created on exiting and re-entering the water may act as a target for echolocation by other individuals in the school. Spinning may also be simply playing. Individuals have been spotted completing at least 14 spinning jumps in quick succession.

In the Atlantic Ocean the Spinner Dolphins may be mistaken for the Clymene Dolphin which also spins, but not to such a regular and dramatic extent. Spinner Dolphins may occasionally mate with other species such as Bottlenose Dolphin and both varieties of Spotted Dolphin, and produce hybrid young.
Population and distribution

Spinner Dolphins occur in deep tropical waters in all of the world’s three tropical oceans. Although these dolphins mainly live in the open ocean, they are sometimes found near the shores of tropical island chains such as in the waters off Hawaii. Their greatest population density occurs between the Tropic of Cancer and Tropic of Capricorn. Although described as pantropical the species roughly divides up into geographical areas corresponding to their different subspecies. The total world population is unknown, and it was certainly dramatically reduced by fishing activity in the eastern Pacific Ocean. This species is still regarded as endangered.
Communication

Dolphin sounds appear to be in the form of click-whistles and pulse sounds which are a mix of echolocation and communication. Echolocation sounds enable dolphins to track objects in dim or dark water and to, in effect, see much further than their eyes will allow. Their complex array of whistle sounds are the way that dolphins talk to one another. The spinners can even identify themselves with sounds they make while trailing bubbles from their blowholes — sounds called signature whistles.

These spinner dolphins also communicate by slapping the water with various body parts. For instance, “nose-outs” occur when beak is thrust from the surface. This action is commonly used when the pod is emerging from a rest period. “Tail slaps” are often used to indicate impending danger or to signal a dive. Head slaps, side slaps, and back slaps are most frequently seen as the school begins to pick up speed. Last, and most spectacular, are the spins themselves. Many animals spin repeatedly, with each spin tending to get smaller and smaller, finally finishing up with an emphatic side slap.

The power of the spin can pick up through their echolocation — may be the real purpose of the spin.

Spinner dolphins maximize the effect of this splash by twisting around to land in a belly-flop, or back-flop. Spins are most frequently performed while the school is spread out across the water. A spinning dolphin may be signaling to the others: “here I am. . . . here is where I am going. . . ” The effect of many dolphins spinning and leaping at once, defines what scientists call the envelope of the school — that is, its size, direction, and speed of travel.
Feeding
Dolphins tend to do most of their hunting at night as the “scattering layer” of marine life, which has spent the day at depths of 3000 feet, rises toward the surface to feed on microscopic plant material. It is composed of fish, jellyfish, euphausiids (or krill), squid, shell-less snails, as well as copepods. Before diving into layer, the pod of dolphins gathers together in a kind of rally as if realizing that they are about to embark on a dangerous journey. Indeed, these dolphins are taking a great risk because other predators have gathered as well, such as sharks, which are natural predators of dolphins. The spinners form small subgroups and spread out across the sea. Time after time, the dolphins dive down into the utter darkness at 800 feet, or more. They do not use their teeth to chew but rather to grasp and immobilize their prey.

Despite being separated by several miles of water, the school still coordinates its activities through sound — -and through spinning — which reaches an explosive crescendo in the darkness of night. Using their echolocation, the spinners scan the darkness and, using their whistles, they call members of the school back together and can unite for defense. By dawn, the spinners regroup. Well-fed, they likely will move once again towards the shelter of nearby islands.
Human interaction

Spinner Dolphins have been studied both in the wild and in captivity in Hawaii. Up to two million Spinner Dolphins, mostly eastern and white-bellied varieties, were killed in the thirty years after purse seine fishing for tuna was introduced in the 1950s. The process killed probably half of all Eastern Spinner Dolphins. See Pantropical Spotted Dolphin for a discussion. Although not caught in purse seine nets, spinner dolphins in Hawaii can be subjected to multiple daily visits to their nearshore resting grounds.

Neophocaena-phocaenoides, Finless Porpoise

Neophocaena-phocaenoides

 Finless Porpoise

The FinNeophocaena-phocaenoides, Finless Porpoiseless Porpoise (Neophocaena phocaenoides) is one of six porpoise species. In the waters around Japan, at the northern end of its range, it is known as the sunameri. A freshwater population found in the Yangtze River in China is known locally as the jiangzhu or “river pig”.

The Finless Porpoise lives in the coastal waters of Asia, especially around India, China, Indonesia and Japan. A unique fresh water population is found in the Yangtze River. At the western end, their range includes the length of the western coast of India and continues up into the Persian Gulf. Throughout their range, the porpoises stay in shallow waters (up to 50 m [160 ft]), close to the shore, in waters with soft or sandy seabeds. In exceptional cases they have been encountered as far as 160 kilometres (100 miles) off-shore in the East China and Yellow Seas, albeit still in shallow water.

Physical description

The Finless Porpoise almost completely lacks a dorsal fin. Instead there is a low ridge covered in thick denticulated skin. This demonstrates that the body shape that has evolved to be the optimum for sharks, dolphins and porpoises is not the only possible body shape for a marine animal.

Adult Finless Porpoises are a uniform light grey colour. Newborn calves are mostly black with grey around the dorsal ridge area, becoming fully grey after 4?6 months. Adults grow more than 1.55 m (5 ft) in length and up to 30?45 kg (65?100 lb) in weight. Males become sexually mature at around 4?6 years of age, and females at around 6?9 years of age.

Diet
The Finless Porpoise, subspecies Neomeris kurrachiensis, in the vicinity of Karachi, British India, now Pakistan, as drawn by R. A. Sterndale, in the Journal of the Bombay Natural History Society, volume 1, number 1, 1886.

Finless Porpoises are reported to eat fish and shrimp in the Yangtze River, and fish, shrimp and squid in the Yellow Sea/Bohai area and off Pakistan. In Japanese waters they are known to eat fish, shrimp, squid, cuttle fish and octopuses. Finless Porpoises are opportunistic feeders utilising various kinds of available food items available in their habitat. Seasonal changes in their diets have not been studied. They also apparently ingest some plant material when living in estuaries, mangroves, and rivers including leaves, rice, and eggs deposited on vegetation.

Schooling

Finless Porpoises are generally found as singles, pairs, or in groups of up to 12, although aggregations of up to about 50 have been reported. Recent data suggests, that the basic unit of a Finless Porpoise pod is a mother/calf pair or two adults, and that schools of three or more individuals are aggregations of these units or of solitary individuals. Social structure seems to be underdeveloped in the species, and the mother/calf pair is probably the only stable social unit.

Behaviour and reproduction

Like other porpoises, their behaviour tends to be not as energetic and showy as that of dolphins. They do not ride bow waves, and in some areas appear to be shy of boats. In the Yangtze River, Finless Porpoises are known to leap from the water and perform “tail stands”. Breeding occurs in late spring and early summer, after a gestation period of 10?11 months. Calves cling to the denticulated area of skin on their mother’s back and are carried by her as she swims. Calves are weaned at 6?15 months.

Swimming style

Although they show no acrobatics in the water, Finless Porpoises are believed to be very active swimmers. They typically swim just beneath the surface of the water and roll to one side when surfacing to breathe. This rolling movement disturbs very little water on the surface, so they are often overlooked when rising to breathe. Surfacing generally lasts for one minute, as they take 3 to 4 quick successive breaths, then quickly submerge into the water. The Finless Porpoise often surfaces a great distance from the point where it dives beneath the water’s surface.

Conservation

There are not enough data to place Finless Porpoises on the endangered species list, except in China, where they are endangered. Since this species is the most coastal of all porpoises, it has the most interaction with humans. This interaction often puts the Finless Porpoise at risk. Like other porpoises, large members of this species are killed by entanglement in gill nets. Except for being briefly hunted after World War II due to the lack of seaworthy fishing boats, Finless Porposes have never been widely hunted in Japan. It is a species protected since 1930 at the area around Awajima Island, Takehara and this coverage had since been extended to all Japanese coastal waters. The primary danger to the species is the environmental degradation. In addition, unlike other members of this family, Finless porpoises have lived under captivity for over 15 years.

There are no well established estimates of the animals’ abundance. However, a comparison of two surveys, one from the late 1970s and the other from 1999?2000 shows a decline in population and distribution. Scientists believe that this decline has been ongoing for decades and that the current population is just a fraction of its historic levels. A 2006 expedition estimated that fewer than 400 of animals survived in the Yangtze River.

At the end of 2006 it was estimated that there are about 1400 porpoises left living in China, with between 700 and 900 in the Yangtze, with about another 500 in Poyang and Dongting Lakes.

2007 population levels are less than half the 1997 levels, and the population is dropping at a rate of 7.3 per cent per year. Current conservation efforts were undertaken alongside those for the recently functionally extinct Baiji. In 1990 5 individuals were relocated to the Tian-e-Zhou Oxbow Nature Reserve and now a population of 28 currently habituate the lake.

Sand dredging has become a mainstay of local economic development in the last few years, and it is an important source of revenue in the region that borders Poyang Lake. But at the same time, high-density dredging projects have been the principal cause of the death of the local wildlife population.

Dredging makes the waters of the lake muddier, and the porpoises cannot see as far as they once could, and have to rely on their highly-developed sonar systems to avoid obstacles and look for food. Large ships enter and leave the lake at the rate of two a minute and such a high density of shipping means the porpoises have difficulty hearing their food, and also cannot swim freely from one bank to the other.

 

Balaenoptera musculus, Blue whale

Balaenoptera musculus

 Blue whale

The Blue Whale (Balaenoptera musculus) is a marine mammal belonging to the suborder of baleen whales (called Mysticeti). AtBalaenoptera musculus, Blue whaleup to 32.9 metres (108 ft)in length and 172 metric tons (190 short tons)[4] or more in weight, it is the largest animal ever known to have existed.

Long and slender, the Blue Whale’s body can be various shades of bluish-grey dorsally and somewhat lighter underneath. There are at least three distinct subspecies: B. m. musculus of the North Atlantic and North Pacific, B. m. intermedia of the Southern Ocean and B. m. brevicauda (also known as the Pygmy Blue Whale) found in the Indian Ocean and South Pacific Ocean. B. m. indica, found in the Indian Ocean, may be another subspecies. As with other baleen whales, its diet consists almost exclusively of small crustaceans known as krill.

Blue Whales were abundant in nearly all the oceans until the beginning of the twentieth century. For over 40 years, they were hunted almost to extinction by whalers until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 Blue Whales worldwide[8], located in at least five groups. More recent research into the Pygmy subspecies suggests this may be an underestimate.[9] Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (range 202,000 to 311,000). There remain only much smaller (around 2,000) concentrations in each of the North-East Pacific, Antarctic, and Indian Ocean groups. There are two more groups in the North Atlantic, and at least two in the Southern Hemisphere.

Blue Whales are rorquals (family Balaenopteridae), a family that includes the Humpback Whale, the Fin Whale, Bryde’s Whale, the Sei Whale and the Minke Whale. The family Balaenopteridae is believed to have diverged from the other families of the suborder Mysticeti as long ago as the middle Oligocene. However, it is not known when the members of those families diverged from each other.

The Blue Whale is usually classified as one of eight species in the genus Balaenoptera; one authority places it in a separate monotypic genus, Sibbaldus, but this is not accepted elsewhere. DNA sequencing analysis indicates that the Blue Whale is phylogenetically closer to the Sei Whale (Balaenoptera borealis) and Bryde’s Whale (Balaenoptera brydei) than to other Balaenoptera species, and closer to the Humpback Whale (Megaptera) and the Gray Whale (Eschrichtius) than to the minke whales (Balaenoptera acutorostrata and Balaenoptera bonaerensis). If further research confirms these relationships, it will be necessary to reclassify the rorquals.

There have been at least 11 documented cases of Blue/Fin hybrid adults in the wild. Arnason and Gullberg describe the genetic distance between a Blue and a Fin as about the same as that between a human and a gorilla. Researchers working off of Fiji believe they photographed a hybrid Humpback/Blue Whale.

The specific name musculus is Latin and could mean “muscular”, but it can also be interpreted as “little mouse”. Linnaeus, who named the species in his seminal Systema Naturae of 1758, would have known this and may have intended the ironic double meaning. Herman Melville called this species Sulphur-bottom in his novel Moby-Dick due to an orange-brown or yellow tinge on the underparts from diatom films on the skin. Other common names for the Blue Whale have included the Sibbald’s Rorqual (after Sir Robert Sibbald), the Great Blue Whale and the Great Northern Rorqual. These names have now fallen into disuse.

Authorities classify the species into three or four subspecies: B. m. musculus, the Northern Blue Whale consisting of the North Atlantic and North Pacific populations, B. m. intermedia, the Southern Blue Whale of the Southern Ocean, B. m. brevicauda, the Pygmy Blue Whale found in the Indian Ocean and South Pacific, and the more problematic B. m. indica, the Great Indian Rorqual, which is also found in the Indian Ocean and, although described earlier, may be the same subspecies as B. m. brevicauda.
Description and behaviour
Adult Blue Whale
The Blue Whale has a long tapering body that appears stretched in comparison with the stockier build of other whales. The head is flat and U-shaped and has a prominent ridge running from the blowhole to the top of the upper lip. The front part of the mouth is thick with baleen plates; around 300 plates (each around one metre (3.2 ft) long) hang from the upper jaw, running 0.5 m (1.6 ft) back into the mouth. Between 60 and 90 grooves (called ventral pleats) run along the throat parallel to the body. These pleats assist with evacuating water from the mouth after lunge feeding .

The dorsal fin is small, visible only briefly during the dive sequence. Located around three-quarters of the way along the length of the body, it varies in shape from one individual to another; some only have a barely perceptible lump, but others may have prominent and falcate dorsals. When surfacing to breathe, the Blue Whale raises its shoulder and blowhole out of the water to a greater extent than other large whales such as the Fin or Sei. Observers can use this trait to differentiate between species at sea. Some Blue Whales in the North Atlantic and North Pacific raise their tail fluke when diving. When breathing, the whale emits a spectacular vertical single-column spout up to 12 metres (39 ft), typically 9 metres (30 ft). Its lung capacity is 5,000 litres (1320 U.S. gallons). Blue whales have twin blowholes shielded by a large splashguard.

The flippers are 3–4 metres (9.8–13 ft) long. The upper sides are grey with a thin white border. The lower sides are white. The head and tail fluke are generally uniformly grey. The whale’s upper parts, and sometimes the flippers, are usually mottled. The degree of mottling varies substantially from individual to individual. Some may have a uniform slate-grey color, but others demonstrate a considerable variation of dark blues, greys and blacks, all tightly mottled.

Blue Whales can reach speeds of 50 kilometres per hour (31 mph) over short bursts, usually when interacting with other whales, but 20 kilometres per hour (12 mph) is a more typical traveling speed. When feeding, they slow down to 5 kilometres per hour (3.1 mph).

Blue Whales most commonly live alone or with one other individual. It is not known how long traveling pairs stay together. In locations where there is a high concentration of food, as many as 50 Blue Whales have been seen scattered over a small area. However, they do not form the large close-knit groups seen in other baleen species.
Size

Blue Whales are difficult to weigh because of their size. Most Blue Whales killed by whalers were not weighed whole, but cut up into manageable pieces first. This caused an underestimate of the total weight of the whale, due to the loss of blood and other fluids. Nevertheless, measurements between 150–170 metric tons (170–190 short tons) were recorded of animals up to 27 metres (89 ft) in length. The weight of a 30 metres (98 ft) individual is believed by the American National Marine Mammal Laboratory (NMML) to be in excess of 180 metric tons (200 short tons). The largest Blue Whale accurately weighed by NMML scientists to date was a female that weighed 177 metric tons (195 short tons).

The Blue Whale is the largest animal ever to have lived. The largest known dinosaur of the Mesozoic Era was the Argentinosaurus, which is estimated to have weighed up to 90 metric tons (99 short tons), though a controversial vertebra of Amphicoelias fragillimus may indicate an animal of up to 122 metric tons (134 short tons) and 40–60 metres (130–200 ft).[22] Furthermore, there are weight estimates for the very poorly known Bruhathkayosaurus ranging from 140–220 metric tons (150–240 short tons), besides length estimates up to about 45 metres (150 ft). The extinct fish Leedsichthys may have approached its size. However, complete fossils are difficult to come by, making size comparisons difficult. All these animals are considered to be smaller than the blue whale.

There is some uncertainty about the biggest Blue Whale ever found, as most data comes from Blue Whales killed in Antarctic waters during the first half of the twentieth century and was collected by whalers not well-versed in standard zoological measurement techniques. The longest whales ever recorded were two females measuring 33.6–33.3 metres (110–109 ft)respectively. The longest whale measured by scientists at the NMML was 29.9 metres (98 ft).

A Blue Whale’s tongue weighs around 2.7 metric tons (3.0 short tons) and, when fully expanded, its mouth is large enough to hold up to 90 metric tons (99 short tons) of food and water. Despite the size of its mouth, the dimensions of its throat are such that a Blue Whale cannot swallow an object wider than a beach ball.[26] Its heart weighs 600 kilograms (1,300 lb) and is the largest known in any animal. A Blue Whale’s aorta is about 23 centimetres (9.1 in) in diameter. During the first seven months of its life, a Blue Whale calf drinks approximately 400 litres (100 U.S. gallons) of milk every day. Blue Whale calves gain weight quickly, as much as 90 kilograms (200 lb) every 24 hours. Even at birth, they weigh up to 2,700 kilograms (6,000 lb)—the same as a fully grown hippopotamus.
Feeding

Blue Whales feed almost exclusively on krill, though they also take small numbers of copepods.[28] The species of this zooplankton eaten by Blue Whales varies from ocean to ocean. In the North Atlantic, Meganyctiphanes norvegica, Thysanoessa raschii, Thysanoessa inermis and Thysanoessa longicaudata are the usual food; in the North Pacific, Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, Thysanoessa spinifera, Nyctiphanes symplex and Nematoscelis megalops; and in the Antarctic, Euphausia superba, Euphausia crystallorophias and Euphausia valentin.

An adult Blue Whale can eat up to 40 million krill in a day. The whales always feed in the areas with the highest concentration of krill, sometimes eating up to 3,600 kilograms (7,900 lb) of krill in a single day. This daily calorie requirement of an adult Blue Whale is in the region of 1.5 million. This means that they typically feed at depths of more than 100 metres (330 ft) during the day and only surface-feed at night. Dive times are typically 10 minutes when feeding, though dives of up to 20 minutes are common. The longest recorded dive is 36 minutes[. The whale feeds by lunging forward at groups of krill, taking the animals and a large quantity of water into its mouth. The water is then squeezed out through the baleen plates by pressure from the ventral pouch and tongue. Once the mouth is clear of water, the remaining krill, unable to pass through the plates, are swallowed. The Blue Whale also incidentally consumes small fish, crustaceans and squid caught up with krill.
Life history

Mating starts in late autumn and continues to the end of winter. Little is known about mating behaviour or breeding grounds. Females typically give birth once every two to three years at the start of the winter after a gestation period of ten to twelve months. The calf weighs about 2.5 metric tons (2.8 short tons) and is around 7 metres (23 ft) in length. Blue Whale calves drink 380–570 litres (100–150 U.S. gallons) of milk a day. Weaning takes place for about six months, by which time the calf has doubled in length. Sexual maturity is typically reached at eight to ten years, by which time males are at least 20 metres (66 ft) long (or more in the Southern Hemisphere). Females are larger still, reaching sexual maturity at around the age of five, by which they are about 21 metres (69 ft) long.

Scientists estimate that Blue Whales can live for at least 80 years;however, since individual records do not date back into the whaling era, this will not be known with certainty for many years. The longest recorded study of a single individual is 34 years, in the north-east Pacific. The whales’ only natural predator is the Orca.[42] Studies report that as many as 25% of mature Blue Whales have scars resulting from Orca attacks. The mortality rate of such attacks is unknown.

Blue Whale strandings are extremely uncommon, and, because of the species’ social structure, mass strandings are unheard of. However, when strandings do occur, they can become the focus of public interest. In 1920, a Blue Whale washed up near Bragar on the Isle of Lewis in the Outer Hebrides of Scotland. It had been shot in the head by whalers, but the harpoon had failed to explode. As with other mammals, the fundamental instinct of the whale was to try to carry on breathing at all costs, even though this meant beaching to prevent itself from drowning. Two of the whale’s bones were erected just off a main road on Lewis and remain a tourist attraction.

The reason for vocalization is unknown. Richardson et al. (1995) discuss six possible reasons:[47]

1. Maintenance of inter-individual distance
2. Species and individual recognition
3. Contextual information transmission (e.g., feeding, alarm, courtship)
4. Maintenance of social organization (e.g., contact calls between females and males)
5. Location of topographic features
6. Location of prey resources

Population and whaling
Hunting era
Main article: History of whaling
Blue Whale populations have declined dramatically due to commercial whaling.

Blue Whales are not easy to catch or kill. Their speed and power meant that they were rarely pursued by early whalers, who instead targeted Sperm and Right Whales.[48] In 1864, the Norwegian Svend Foyn equipped a steamboat with harpoons specifically designed for catching large whales.[3] Although initially cumbersome and with a low success rate, Foyn perfected the harpoon gun, and soon several whaling stations were established on the coast of Finnmark in northern Norway. Because of disputes with the local fishermen, the last whaling station in Finnmark was closed down in 1904.

Soon, Blue Whales were being hunted in Iceland (1883), the Faroe Islands (1894), Newfoundland (1898), and Spitsbergen (1903). In 1904-05 the first Blue Whales were taken off South Georgia. By 1925, with the advent of the stern slipway in factory ships and the use of steam-driven whale catchers, the catch of Blue Whales, and baleen whales as a whole, in the Antarctic and sub-Antarctic began to increase dramatically. Between 1930 and 1931, these ships killed 29,400 Blue Whales in the Antarctic alone. By the end of World War II, populations had been significantly depleted, and, in 1946, the first quotas restricting international trade in whales were introduced, but they were ineffective because of the lack of differentiation between species. Rare species could be hunted on an equal footing with those found in relative abundance.

Blue Whale hunting was banned in the 1960s by the International Whaling Commission, and illegal whaling by the USSR finally halted in the 1970s, by which time 330,000 Blue Whales had been killed in the Antarctic, 33,000 in the rest of the Southern Hemisphere, 8,200 in the North Pacific, and 7,000 in the North Atlantic. The largest original population, in the Antarctic, had been reduced to 0.15% of their initial numbers.
Population and distribution today

Since the introduction of the whaling ban, studies have failed to ascertain whether the conservation reliant global Blue Whale population is increasing or remaining stable. In the Antarctic, best estimates show a significant increase at 7.3% per year since the end of illegal Soviet whaling, but numbers remain at under 1% of their original levels.[ It has also been suggested that Icelandic and Californian populations are increasing but these increases are not statistically significant. The total world population was estimated to be between 5,000 and 12,000 in 2002, although there are high levels of uncertainty in available estimates for many areas.

The IUCN Red List counts the Blue Whale as “endangered” as it has since the list’s inception. In the United States, the National Marine Fisheries Service lists them as endangered under the Endangered Species Act.[52] The largest known concentration, consisting of about 2,000 individuals, is the North-East Pacific population of the Northern Blue Whale (B. m. musculus) subspecies that ranges from Alaska to Costa Rica but is most commonly seen from California in summer. Infrequently, this population visits the North-West Pacific between Kamchatka and the northern tip of Japan.

In the North Atlantic, two stocks of B. m. musculus are recognized. The first is found off Greenland, Newfoundland, Nova Scotia and the Gulf of Saint Lawrence. This group is estimated to total about 500. The second, more easterly group is spotted from the Azores in spring to Iceland in July and August; it is presumed that the whales follow the Mid-Atlantic Ridge between the two volcanic islands. Beyond Iceland, Blue Whales have been spotted as far north as Spitsbergen and Jan Mayen, though such sightings are rare. Scientists do not know where these whales spend their winters. The total North Atlantic population is estimated to be between 600 and 1,500.

In the Southern Hemisphere, there appear to be two distinct subspecies, B. m. intermedia, the Antarctic Blue Whale, and the little-studied Pygmy Blue Whale, B. m. brevicauda, found in Indian Ocean waters. The most recent surveys (midpoint 1998) provided an estimate of 2,280 blue whales in the Antarctic., of which fewer than 1% are likely to be pygmy blue whales Estimates from a 1996 survey were that 424 Pygmy Blue Whales were in a small area south of Madagascar alone, thus it is likely that numbers in the entire Indian Ocean are in the thousands. If this is true, the global numbers would be much higher than estimates predict.

A fourth subspecies, B. m. indica, was identified by Blyth in 1859 in the northern Indian Ocean, but difficulties in identifying distinguishing features for this subspecies led to it being used a synonym for B. m. brevicauda, the Pygmy Blue Whale. Records for Soviet catches seem to indicate that the female adult size is closer to that of the Pygmy Blue than B. m. musculus, although the populations of B. m. indica and B. m. brevicauda appear to be discrete, and the breeding seasons differ by almost six months.
Migratory patterns of these subspecies are not well known. For example, Pygmy Blue Whales have been recorded in the northern Indian Ocean (Oman, Maldives, Sri Lanka), where they may form a distinct resident population. In addition, the population of Blue Whales occurring off Chile and Peru may also be a distinct population. Some Antarctic Blue Whales approach the eastern South Atlantic coast in winter, and occasionally, their vocalizations are heard off Peru, Western Australia, and in the northern Indian Ocean. In Chile, the Cetacean Conservation Center, with support from the Chilean Navy, is undertaking extensive research and conservation work on a recently discovered feeding aggregation of the species off the coast of Chiloe Island in an area named “Golfo del Corcovado”, where 326 Blue Whales were spotted in the summer of 2007.

Efforts to calculate the Blue Whale population more accurately are supported by marine mammologists at Duke University who maintain the OBIS-SEAMAP (Ocean Biogeographic Information System—Spatial Ecological Analysis of Megavertebrate Populations), a collation of marine mammal sighting data from around 130 sources.
Threats other than hunting
A blue whale surfaces off Santa Cruz Island in the Channel Islands, near Santa Barbara, CA

Due to their enormous size, power and speed, adult Blue Whales have virtually no natural predators. There is, however, one documented case in National Geographic Magazine of a Blue Whale being attacked by Orcas; although the Orcas were unable to kill the animal outright during their attack, the Blue Whale sustained massive wounds and probably died as a result of them shortly after the attack.

Blue Whales may be wounded, sometimes fatally, after colliding with ocean vessels as well as becoming trapped or entangled in fishing gear. The ever-increasing amount of ocean noise, including sonar, drowns out the vocalizations produced by whales, which may make it harder for them to communicate. Human threats to the potential recovery of Blue Whale populations also include accumulation of polychlorinated biphenyl (PCB) chemicals within the whale’s body.

With global warming causing glaciers and permafrost to melt rapidly and allowing a large amount of fresh water to flow into the oceans, there are concerns that if the amount of fresh water in the oceans reaches a critical point, there will be a disruption in the thermohaline circulation. Considering the Blue Whale’s migratory patterns are based on ocean temperature, a disruption in this circulation, which moves warm and cold water around the world, would be likely to have an effect on their migration. The whales summer in the cool, high latitudes, where they feed in krill-abundant waters; they winter in warmer, low latitudes, where they mate and give birth.

The change in ocean temperature would also affect the Blue Whale’s food supply. The warming trend and decreased salinity levels would cause a significant shift in krill location and abundance.
Museums

The Natural History Museum in London contains a famous mounted skeleton and life-size model of a Blue Whale, which were both the first of their kind in the world but have since been replicated at the University of California, Santa Cruz. Similarly, the American Museum of Natural History in New York City has a full-size model in its Milstein Family Hall of Ocean Life.

The Aquarium of the Pacific in Long Beach, California features a life-size model of a mother Blue Whale with her calf suspended from the ceiling of its main hall.
Whale-watching

Living Blue Whales may be encountered on whale-watching cruises in the Gulf of Maine and are the main attractions along the north shore of the Gulf of Saint Lawrence and in the Saint Lawrence estuary.

Balaenoptera-musculus, Blue Whale, Paus biru

Balaenoptera-musculus

 Blue Whale, Paus biru

The Blue WhBalaenoptera-musculus, Blue Whale, Paus biruale (Balaenoptera musculus) is a marine mammal belonging to the suborder of baleen whales (called Mysticeti). At up to 32.9 metres (108 ft)in length and 172 metric tons (190 short tons) or more in weight, it is the largest animal ever known to have existed.

Long and slender, the Blue Whale’s body can be various shades of bluish-grey dorsally and somewhat lighter underneath. There are at least three distinct subspecies: B. m. musculus of the North Atlantic and North Pacific, B. m. intermedia of the Southern Ocean and B. m. brevicauda (also known as the Pygmy Blue Whale) found in the Indian Ocean and South Pacific Ocean. B. m. indica, found in the Indian Ocean, may be another subspecies. As with other baleen whales, its diet consists almost exclusively of small crustaceans known as krill.

Blue Whales were abundant in nearly all the oceans until the beginning of the twentieth century. For over 40 years, they were hunted almost to extinction by whalers until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 Blue Whales worldwide, located in at least five groups. More recent research into the Pygmy subspecies suggests this may be an underestimate.Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (range 202,000 to 311,000). There remain only much smaller (around 2,000) concentrations in each of the North-East Pacific, Antarctic, and Indian Ocean groups. There are two more groups in the North Atlantic, and at least two in the Southern Hemisphere.

The Blue Whale has a long tapering body that appears stretched in comparison with the stockier build of other whales. The head is flat and U-shaped and has a prominent ridge running from the blowhole to the top of the upper lip.The front part of the mouth is thick with baleen plates; around 300 plates (each around one metre (3.2 ft) long) hang from the upper jaw, running 0.5 m (1.6 ft) back into the mouth. Between 60 and 90 grooves (called ventral pleats) run along the throat parallel to the body. These pleats assist with evacuating water from the mouth after lunge feeding (see feeding below).

The dorsal fin is small, visible only briefly during the dive sequence. Located around three-quarters of the way along the length of the body, it varies in shape from one individual to another; some only have a barely perceptible lump, but others may have prominent and falcate dorsals. When surfacing to breathe, the Blue Whale raises its shoulder and blowhole out of the water to a greater extent than other large whales such as the Fin or Sei. Observers can use this trait to differentiate between species at sea. Some Blue Whales in the North Atlantic and North Pacific raise their tail fluke when diving. When breathing, the whale emits a spectacular vertical single-column spout up to 12 metres (39 ft), typically 9 metres (30 ft). Its lung capacity is 5,000 litres (1320 U.S. gallons). Blue whales have twin blowholes shielded by a large splashguard.[20]

The flippers are 3?4 metres (9.8?13 ft) long. The upper sides are grey with a thin white border. The lower sides are white. The head and tail fluke are generally uniformly grey. The whale’s upper parts, and sometimes the flippers, are usually mottled. The degree of mottling varies substantially from individual to individual. Some may have a uniform slate-grey color, but others demonstrate a considerable variation of dark blues, greys and blacks, all tightly mottled.

Blue Whales can reach speeds of 50 kilometres per hour (31 mph) over short bursts, usually when interacting with other whales, but 20 kilometres per hour (12 mph) is a more typical traveling speed. When feeding, they slow down to 5 kilometres per hour (3.1 mph).

Blue Whales most commonly live alone or with one other individual. It is not known how long traveling pairs stay together. In locations where there is a high concentration of food, as many as 50 Blue Whales have been seen scattered over a small area. However, they do not form the large close-knit groups seen in other baleen species.

Size

Blue Whales are difficult to weigh because of their size. Most Blue Whales killed by whalers were not weighed whole, but cut up into manageable pieces first. This caused an underestimate of the total weight of the whale, due to the loss of blood and other fluids. Nevertheless, measurements between 150?170 metric tons (170?190 short tons) were recorded of animals up to 27 metres (89 ft) in length. The weight of a 30 metres (98 ft) individual is believed by the American National Marine Mammal Laboratory (NMML) to be in excess of 180 metric tons (200 short tons). The largest Blue Whale accurately weighed by NMML scientists to date was a female that weighed 177 metric tons (195 short tons).

The Blue Whale is the largest animal ever to have lived. The largest known dinosaur of the Mesozoic Era was the Argentinosaurus, which is estimated to have weighed up to 90 metric tons (99 short tons), though a controversial vertebra of Amphicoelias fragillimus may indicate an animal of up to 122 metric tons (134 short tons) and 40?60 metres (130?200 ft).[22] Furthermore, there are weight estimates for the very poorly known Bruhathkayosaurus ranging from 140?220 metric tons (150?240 short tons), besides length estimates up to about 45 metres (150 ft). The extinct fish Leedsichthys may have approached its size. However, complete fossils are difficult to come by, making size comparisons difficult. All these animals are considered to be smaller than the blue whale.

There is some uncertainty about the biggest Blue Whale ever found, as most data comes from Blue Whales killed in Antarctic waters during the first half of the twentieth century and was collected by whalers not well-versed in standard zoological measurement techniques. The longest whales ever recorded were two females measuring 33.6?33.3 metres (110?109 ft)respectively.[24] The longest whale measured by scientists at the NMML was 29.9 metres (98 ft).A Blue Whale’s tongue weighs around 2.7 metric tons (3.0 short tons) and, when fully expanded, its mouth is large enough to hold up to 90 metric tons (99 short tons) of food and water. Despite the size of its mouth, the dimensions of its throat are such that a Blue Whale cannot swallow an object wider than a beach ball.[26] Its heart weighs 600 kilograms (1,300 lb) and is the largest known in any animal. A Blue Whale’s aorta is about 23 centimetres (9.1 in) in diameter.During the first seven months of its life, a Blue Whale calf drinks approximately 400 litres (100 U.S. gallons) of milk every day. Blue Whale calves gain weight quickly, as much as 90 kilograms (200 lb) every 24 hours. Even at birth, they weigh up to 2,700 kilograms (6,000 lb)?the same as a fully grown hippopotamus.

Feeding

Blue Whales feed almost exclusively on krill, though they also take small numbers of copepods.[28] The species of this zooplankton eaten by Blue Whales varies from ocean to ocean. In the North Atlantic, Meganyctiphanes norvegica, Thysanoessa raschii, Thysanoessa inermis and Thysanoessa longicaudata are the usual food; in the North Pacific, Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, Thysanoessa spinifera, Nyctiphanes symplex and Nematoscelis megalops; and in the Antarctic, Euphausia superba, Euphausia crystallorophias and Euphausia valentin.

An adult Blue Whale can eat up to 40 million krill in a day. The whales always feed in the areas with the highest concentration of krill, sometimes eating up to 3,600 kilograms (7,900 lb) of krill in a single day.This daily calorie requirement of an adult Blue Whale is in the region of 1.5 million. This means that they typically feed at depths of more than 100 metres (330 ft) during the day and only surface-feed at night. Dive times are typically 10 minutes when feeding, though dives of up to 20 minutes are common. The longest recorded dive is 36 minutes. The whale feeds by lunging forward at groups of krill, taking the animals and a large quantity of water into its mouth. The water is then squeezed out through the baleen plates by pressure from the ventral pouch and tongue. Once the mouth is clear of water, the remaining krill, unable to pass through the plates, are swallowed. The Blue Whale also incidentally consumes small fish, crustaceans and squid caught up with krill.

Life history

Mating starts in late autumn and continues to the end of winter. Little is known about mating behaviour or breeding grounds. Females typically give birth once every two to three years at the start of the winter after a gestation period of ten to twelve months.[40] The calf weighs about 2.5 metric tons (2.8 short tons) and is around 7 metres (23 ft) in length. Blue Whale calves drink 380?570 litres (100?150 U.S. gallons) of milk a day. Weaning takes place for about six months, by which time the calf has doubled in length. Sexual maturity is typically reached at eight to ten years, by which time males are at least 20 metres (66 ft) long (or more in the Southern Hemisphere). Females are larger still, reaching sexual maturity at around the age of five, by which they are about 21 metres (69 ft) long.

Scientists estimate that Blue Whales can live for at least 80 years;[24][40][41] however, since individual records do not date back into the whaling era, this will not be known with certainty for many years. The longest recorded study of a single individual is 34 years, in the north-east Pacific.[37] The whales’ only natural predator is the Orca. Studies report that as many as 25% of mature Blue Whales have scars resulting from Orca attacks.The mortality rate of such attacks is unknown.

Blue Whale strandings are extremely uncommon, and, because of the species’ social structure, mass strandings are unheard of. However, when strandings do occur, they can become the focus of public interest. In 1920, a Blue Whale washed up near Bragar on the Isle of Lewis in the Outer Hebrides of Scotland. It had been shot in the head by whalers, but the harpoon had failed to explode. As with other mammals, the fundamental instinct of the whale was to try to carry on breathing at all costs, even though this meant beaching to prevent itself from drowning. Two of the whale’s bones were erected just off a main road on Lewis and remain a tourist attraction.

Estimates made by Cummings and Thompson (1971) suggest that source level of sounds made by Blue Whales are between 155 and 188 decibels when measured relative to a reference pressure of one micropascal at one metre. All Blue Whale groups make calls at a fundamental frequency of between 10 and 40 Hz, and the lowest frequency sound a human can typically perceive is 20 Hz. Blue Whale calls last between ten and thirty seconds. Blue Whales off the coast of Sri Lanka have been repeatedly recorded making “songs” of four notes duration lasting about two minutes each, reminiscent of the well-known Humpback Whale songs. Researchers believe that as this phenomenon has not been seen in any other populations, it may be unique to the B. m. brevicauda (Pygmy) subspecies.

The reason for vocalization is unknown. Richardson et al. (1995) discuss six possible reasons:

1. Maintenance of inter-individual distance
2. Species and individual recognition
3. Contextual information transmission (e.g., feeding, alarm, courtship)
4. Maintenance of social organization (e.g., contact calls between females and males)
5. Location of topographic features
6. Location of prey resources

Population and whaling

Blue Whales are not easy to catch or kill. Their speed and power meant that they were rarely pursued by early whalers, who instead targeted Sperm and Right Whales. In 1864, the Norwegian Svend Foyn equipped a steamboat with harpoons specifically designed for catching large whales. Although initially cumbersome and with a low success rate, Foyn perfected the harpoon gun, and soon several whaling stations were established on the coast of Finnmark in northern Norway. Because of disputes with the local fishermen, the last whaling station in Finnmark was closed down in 1904.

Soon, Blue Whales were being hunted in Iceland (1883), the Faroe Islands (1894), Newfoundland (1898), and Spitsbergen (1903). In 1904-05 the first Blue Whales were taken off South Georgia. By 1925, with the advent of the stern slipway in factory ships and the use of steam-driven whale catchers, the catch of Blue Whales, and baleen whales as a whole, in the Antarctic and sub-Antarctic began to increase dramatically. Between 1930 and 1931, these ships killed 29,400 Blue Whales in the Antarctic alone. By the end of World War II, populations had been significantly depleted, and, in 1946, the first quotas restricting international trade in whales were introduced, but they were ineffective because of the lack of differentiation between species. Rare species could be hunted on an equal footing with those found in relative abundance.

Blue Whale hunting was banned in the 1960s by the International Whaling Commission, and illegal whaling by the USSR finally halted in the 1970s,[51] by which time 330,000 Blue Whales had been killed in the Antarctic, 33,000 in the rest of the Southern Hemisphere, 8,200 in the North Pacific, and 7,000 in the North Atlantic. The largest original population, in the Antarctic, had been reduced to 0.15% of their initial numbers.

Population and distribution today

Since the introduction of the whaling ban, studies have failed to ascertain whether the conservation reliant global Blue Whale population is increasing or remaining stable. In the Antarctic, best estimates show a significant increase at 7.3% per year since the end of illegal Soviet whaling, but numbers remain at under 1% of their original levels.[10] It has also been suggested that Icelandic and Californian populations are increasing but these increases are not statistically significant. The total world population was estimated to be between 5,000 and 12,000 in 2002, although there are high levels of uncertainty in available estimates for many areas.

The Blue Whale remains listed as “endangered” on the IUCN Red List of threatened species as it has been since the list’s inception. The largest known concentration, consisting of about 2,000 individuals, is the North-East Pacific population of the Northern Blue Whale (B. m. musculus) subspecies that ranges from Alaska to Costa Rica but is most commonly seen from California in summer. Sometimes, this population strays over to the North-West Pacific; infrequent sightings between Kamchatka and the northern tip of Japan have been recorded.

In the North Atlantic, two stocks of B. m. musculus are recognized. The first is found off Greenland, Newfoundland, Nova Scotia and the Gulf of Saint Lawrence. This group is estimated to total about 500. The second, more easterly group is spotted from the Azores in spring to Iceland in July and August; it is presumed that the whales follow the Mid-Atlantic Ridge between the two volcanic islands. Beyond Iceland, Blue Whales have been spotted as far north as Spitsbergen and Jan Mayen, though such sightings are rare. Scientists do not know where these whales spend their winters. The total North Atlantic population is estimated to be between 600 and 1,500.

In the Southern Hemisphere, there appear to be two distinct subspecies, B. m. intermedia, the Antarctic Blue Whale, and the little-studied Pygmy Blue Whale, B. m. brevicauda, found in Indian Ocean waters. The most recent surveys (midpoint 1998) provided an estimate of 2,280 blue whales in the Antarctic., of which fewer than 1% are likely to be pygmy blue whales Estimates from a 1996 survey were that 424 Pygmy Blue Whales were in a small area south of Madagascar alone,[54] thus it is likely that numbers in the entire Indian Ocean are in the thousands. If this is true, the global numbers would be much higher than estimates predict.

A fourth subspecies, B. m. indica, was identified by Blyth in 1859 in the northern Indian Ocean, but difficulties in identifying distinguishing features for this subspecies led to it being used a synonym for B. m. brevicauda, the Pygmy Blue Whale. Records for Soviet catches seem to indicate that the female adult size is closer to that of the Pygmy Blue than B. m. musculus, although the populations of B. m. indica and B. m. brevicauda appear to be discrete, and the breeding seasons differ by almost six months.

Migratory patterns of these subspecies are not well known. For example, Pygmy Blue Whales have been recorded in the northern Indian Ocean (Oman, Maldives, Sri Lanka), where they may form a distinct resident population.[55] In addition, the population of Blue Whales occurring off Chile and Peru may also be a distinct population. Some Antarctic Blue Whales approach the eastern South Atlantic coast in winter, and occasionally, their vocalizations are heard off Peru, Western Australia, and in the northern Indian Ocean.[55] In Chile, the Cetacean Conservation Center, with support from the Chilean Navy, is undertaking extensive research and conservation work on a recently discovered feeding aggregation of the species off the coast of Chiloe Island in an area named “Golfo del Corcovado”, where 326 Blue Whales were spotted in the summer of 2007.

Efforts to calculate the Blue Whale population more accurately are supported by marine mammologists at Duke University who maintain the OBIS-SEAMAP (Ocean Biogeographic Information System?Spatial Ecological Analysis of Megavertebrate Populations), a collation of marine mammal sighting data from around 130 sources.Threats other than hunting
A blue whale surfaces off Santa Cruz Island in the Channel Islands, near Santa Barbara, CA

Due to their enormous size, power and speed, adult Blue Whales have virtually no natural predators. There is, however, one documented case in National Geographic Magazine of a Blue Whale being attacked by Orcas; although the Orcas were unable to kill the animal outright during their attack, the Blue Whale sustained massive wounds and probably died as a result of them shortly after the attack.[58]

Blue Whales may be wounded, sometimes fatally, after colliding with ocean vessels as well as becoming trapped or entangled in fishing gear. The ever-increasing amount of ocean noise, including sonar, drowns out the vocalizations produced by whales, which may make it harder for them to communicate. Human threats to the potential recovery of Blue Whale populations also include accumulation of polychlorinated biphenyl (PCB) chemicals within the whale’s body.

With global warming causing glaciers and permafrost to melt rapidly and allowing a large amount of fresh water to flow into the oceans, there are concerns that if the amount of fresh water in the oceans reaches a critical point, there will be a disruption in the thermohaline circulation. Considering the Blue Whale’s migratory patterns are based on ocean temperature, a disruption in this circulation, which moves warm and cold water around the world, would be likely to have an effect on their migration. The whales summer in the cool, high latitudes, where they feed in krill-abundant waters; they winter in warmer, low latitudes, where they mate and give birth.

The change in ocean temperature would also affect the Blue Whale’s food supply. The warming trend and decreased salinity levels would cause a significant shift in krill location and abundance.

 

Delphinus capensis, Long-beaked common dolphin

Delphinus capensis

 Long-beaked common dolphin

The Long-beakeDelphinus capensis, Long-beaked common dolphind Common Dolphin (Delphinus capensis) is a species of common dolphin. It has a more restricted range than the Short-beaked Common Dolphin (D. delphis). It has a disjointed range in coastal areas in tropical and warmer temperate oceans. The range includes parts of western and southern Africa, much of western South America, southern California to central Mexico, coastal Peru, areas around Japan, Korea and Taiwan, and possibly near Oman.

The Long-beaked Common dolphin is a medium sized dolphin, smaller than the more popular bottlenose dolphin. Adults range between 1.9 and 2.5 metres (6.2 and 8.2 ft), long, and can weigh between 80 and 235 kilograms (180 and 520 lb), although a range between 80 and 150 kilograms (180 and 330 lb) is more common. Males are generally longer and heavier. The color pattern on the body is unusual. The back is dark and the belly is white, while on each side is an hourglass pattern colored light grey, yellow or gold in front and dirty grey in back. It has a long, thin rostrum with up to 50–60 small, sharp, interlocking teeth on each side of each jaw.
Taxonomy

The Short-beaked Common Dolphin is a member of common dolphin genus, Delphinus within the dolphin family, Delphinidae. Until the mid-1990s, the different forms within Delphinus were not recognized as separate species, but were all considered members of the species D. delphis.Currently, there are two recognized species of Delphinus — the Short-beaked Common Dolphin (D. delphis) and the Long-beaked Common Dolphin. The Long-beaked Common Dolphin is generally larger than the Short-beaked Common Dolphin and has a longer rostrum.

The Indo-Pacific Common Dolphin is sometimes considered a separate species (D. tropicalis) but is more often considered a form of the Long-beaked Common Dolphin.
Behavior

Long-beaked Common Dolphins can live in aggregations of hundreds or even thousands of dolphins.[3] They sometimes associate with other dolphin species, such as pilot whales.[3] They have also been observed bow riding on baleen whales, and they also bow ride on boats.[3] Breaching behavior and aerial acrobatics are common with this species.
Diet

The Long-beaked Common Dolphin has a varied diet consisting of many species of fish and squid that live less than 200 metres (660 ft) deep.
Reproduction

The Long-beaked Common Dolphin has a gestation period of 10 to 11 months. The newborn calf has a length of between 80 and 100 centimetres (2.6 and 3.3 ft) and a weight of about 10 kilograms (22 lb).] Typical interbirth interval ranges from 1 to 3 years. In captivity, the Long-beaked Common Dolphin has hybridized with the Common Bottlenose Dolphin (Tursiops truncatus).One of the hybrids has been bred back to a bottlenose dolphin, demonstrating that such hybrids are fertile.

Dugong-dugon, Dugong, Duyung

Dugong-dugon

Dugong, Duyung

The Dugong-dugon, Dugong, Duyungdugong (Dugong dugon) is a large marine mammal which, together with the manatees, is one of four living species of the order Sirenia. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller’s Sea Cow (Hydrodamalis gigas), was hunted to extinction in the 18th century. It is also the only sirenian in its range, which spans the waters of at least 37 countries throughout the Indo-Pacific,though the majority of dugongs live in the northern waters of Australia between Shark Bay and Moreton Bay. The dugong is the only strictly-marine herbivorous mammal, as all species of manatee utilize fresh water to some degree.

Like all modern sirenians, the dugong has a fusiform body with no dorsal fin or hindlimbs, instead possessing paddle-like forelimbs used to maneuver itself. It is easily distinguished from the manatees by its fluked, dolphin-like tail, but also possesses a unique skull and teeth. The dugong is heavily dependent on seagrasses for subsistence and is thus restricted to the coastal habitats where they grow, with the largest dugong concentrations typically occurring in wide, shallow, protected areas such as bays, mangrove channels and the lee sides of large inshore islands. Its snout is sharply down turned, an adaptation for grazing and uprooting benthic seagrasses.

The dugong has been hunted for thousands of years for its meat and oil, although dugong hunting also has great cultural significance throughout its range. The dugong’s current distribution is reduced and disjunct, and many populations are close to extinction. The IUCN lists the dugong as a species vulnerable to extinction, while the Convention on International Trade in Endangered Species limits or bans the trade of derived products based on the population involved. Despite being legally protected in many countries throughout their range, the main causes of population decline remain anthropogenic and include hunting, habitat degradation, and fishing-related fatalities.[8] With its long lifespan of 70 years or more, and slow rate of reproduction, the dugong is especially vulnerable to these types of exploitation. Dugongs are also threatened by storms, parasites, and their natural predators, sharks, killer whales, and crocodiles.The dugong’s body is large and fusiform, with thick, smooth skin that is a pale cream color at birth but darkens dorsally and laterally to a brownish to dark gray with age. The body is sparsely covered in short hair, a common feature among sirenians which may allow for tactile interpretation of their environment. The dugong has paddle-like forelimbs which aid in movement and feeding, while its fluked tail provides locomotion through vertical movement. The teats are located just behind the forelimbs, similar to their location in elephants. Like the Amazonian Manatee, the dugong lacks nails on its forelimbs.

Unlike the manatees, the dugong’s teeth do not continually grow back via horizontal tooth replacement.The dugong has two incisors (tusks) which grow posteriorly until puberty, after which they first erupt in males. The female’s tusks continue to grow posteriorly, sometimes erupting later in life after reaching the base of the premaxilla.

Like other sirenians, the dugong experiences pachyostosis, a condition in which the ribs and other long bones are unusually solid and contain little or no marrow. These heavy bones, which are among the densest in the animal kingdom, may act as a ballast to help keep sirenians suspended slightly below the water’s surface.

Dugongs are generally smaller than manatees (with the exception of the Amazonian Manatee), reaching an average adult length of 2.7 metres (8.9 ft) and weight of 150 to 300 kilograms (330 to 660 lb). An adult’s length rarely exceeds 3 metres (9.8 ft), and females tend to be larger than males. The largest known dugong was a female landed off the Saurashtra coast of west India, measuring 4.03 metres (13.2 ft) and weighing 1,018 kilograms (2,240 lb).

Distribution

Remaining populations of dugong are greatly reduced, although they once covered all of the tropical South Pacific and Indian Oceans.[citation needed] Their historic range is believed to correspond to that of certain seagrasses. Groups of 10,000 or more are present on the Great Barrier Reef of Australia, at Shark Bay, and in Torres Strait south of New Guinea. Before 1970, it is thought, large populations were also present in coastal Mozambique and Kenya, but these have dwindled. Palau also has a small population. On January 22, 2003, an individual was found (weight 300 kg, length 2 m) off the coast of Tanzania.[citation needed]

Moreton Bay in Brisbane, Australia, is one of many homes to the dugong because it contains clean, clear water at the appropriate depth ranges; suitable food; and access to the sea for warmth. Although strong tidal currents affect the exact times and durations of each visit to the bay, the dugong return for protection from large sharks. Important to the future of the dugong, the area is a 200 km stretch of high-density human habitation and recreation, with easy access to study and learn how to best protect the remaining herds.

A small number of dugongs are also found in the Straits of Johor (which separates Johor in Malaysia and Singapore), in the Philippine provinces of Palawan, Romblon, Guimaras and Davao Oriental, in the Arabian Sea along Pakistan and in the Red Sea in Egypt provinces Marsa Alam at Marsa Abu Dabbab. The remaining dugongs in the Persian Gulf have reportedly been further endangered by repeated U.S.-Iraq conflicts which resulted in large oil spills into the gulf. The current population of Persian Gulf dugongs is around 7,500, but their status is currently not well known.

Feeding

Dugongs are referred to as “sea cows” because their diet consists mainly of sea-grass. They are particular about their diets, with certain “fields” of sea-grass being regularly cropped. Unlike manatees, dugongs are exclusively benthic, or bottom, feeders. Their primary feeding mechanism is uprooting sea-grass by digging furrows in the seafloor with their snouts. Reflecting this, the muscular snouts of dugongs are more dramatically tapered than those of manatees.

Dugongs in Moreton Bay, Australia, are omnivorous, feeding on invertebrates such as polychaetes when the supply of their choice grasses decreases. They will also go to any fresh water sources for drinking. Without these fresh water sources, many would not survive. The amount of these fresh water sources is beginning to decline. The dugong population is predicted to enter a steep decline.

Reproduction

Dugongs bear one calf at a time after an apporoximately 13-month gestation. The calf nurses for two years and reaches sexual maturity between the ages of 8-18, longer than in most other mammals. Despite the longevity of the Dugong, which may live for fifty years or more, females give birth only a few times during their life and invest considerable parental care in their young.

There is a 5,000-year old wall painting of a dugong, apparently drawn by neolithic peoples, found in Tambun Cave of Ipoh city in the state of Perak, Malaysia. This was discovered by Lt.R.L Rawlings in 1959 while on a routine patrol.

During the Renaissance and the Baroque eras, dugongs were often exhibited in wunderkammers. They were also presented as Fiji mermaids in sideshows.

In the Bible

The dugong may be referred to in the Bible by the phrase “sea cow” in several places in Exodus (for example, 25:5 & 26:14) and in Numbers. Dugong hides may have been used in the construction of the Tabernacle, if dugong is an accurate translation of the biblical animal tachash.

[edit] Dugong in captivity

Worldwide, only six dugongs are held in captivity. Two are the featured attraction of Toba Aquarium in Japan; another, named Gracie, is at Underwater World, Singapore; a fourth is in Sea World Indonesia [26] which was saved after being caught by a local fisherman; and the last two (Pig, a 10-year-old male, and Wuru, a four-year-old female) used to live in Sea World on the Gold Coast, Queensland, Australia, but in December, 2008, they were relocated to Sydney Aquarium.

Conservation

Dugong are hunted for food throughout their wildlife range, usually for their meat and blubber.[citation needed] The seagrass beds which the dugong depend on for food are threatened by eutrophication caused by agricultural and industrial runoff, and dugong waste matter is a major food source for other aquatic creatures. Due to their shallow-water feeding habits, dugong are frequently injured or killed by collisions with motorized water vessels. Because of their large size, they have only a few predators. These include sharks, killer whales and saltwater crocodiles.

The U.S. and Japanese governments want to build a new military base on a coral reef close to Henoko, in Nago county, Okinawa. This plan has generated strong protests from Okinawans who are concerned that the local environment, home to the dugong, would be ruined.[citation needed] Greenpeace stepped up its campaign protesting the Okinawa base expansion in the summer of 2007, as authorities recommenced their airbase development plans.

Around the waters of Papua New Guinea, natives have been known to hunt both dugongs and dugong predators, such as sharks.

 

Globicephala macrorhynchus, Short-finned pilot whale

Globicephala macrorhynchus

 Short-finned pilot whale

The Short-finned Pilot Whale (GloGlobicephala macrorhynchus, Short-finned pilot whalebicephala macrorhynchus) is one of the two species of cetacean 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 names 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.

Adult males may have a number of scars on their bodies. 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.

Field ID: Stocky body, bulbous forehead, no prominent beak, long flippers sharply pointed at the tip, black or dark grey colour, fin set forward on body, fluke raised before deep dive, may float motionless at the surface, frequently seen in very large groups, prefers deep water, may be approached.

Length (metres): Adults are 3.5 – 6.5 metres in length. When they are born short-finned pilot whales are about 1.4-1.9 metres long.

Weight: At birth, Short-finned Pilot Whales weigh about 60kg (135lb). A fully grown adult will weigh between 1 and 4 tonnes.

Diet: Fish, Squid, Octopus
Behaviour

Short-finned Pilot Whales are very sociable and are rarely seen alone. They are found in groups of ten to thirty, though some pods are as large as sixty. They are sometimes seen logging and will allow boats to get quite close. They rarely breach, but may be seen lobtailing (slapping their flukes on the water surface) and spyhopping (poking their heads above the surface). Before diving, they arch their tails and raise them above the surface. When coming to the surface to breathe, adults tend to show only the top of their head, whereas calves will throw their entire head out of the water. Adults occasionally porpoise (lift most of the body out of the water) when swimming particularly quickly.

They are known as the ‘Cheetahs of the Deep’ for the high speed pursuits of squids at depths of hundreds of metres.

Grampus griseus, Risso’s dolphin

Grampus griseus

 Risso’s dolphin

Risso’s dolphin (Grampus griseus) is the Grampus griseus, Risso's dolphinonly species of dolphin in the genus Grampus.
Risso’s dolphin was first described by Cuvier in 1812. The species’ common name is from Antoine Risso, who described a specimen to Cuvier on which Cuvier made his first description. Another common name for the Risso’s dolphin is the grampus (also the species genus), although as a common name this was historically used for the orca. The etymology of the word grampus is unclear. It may be an aglomeration of the Latin grandis piscis or French grand poisson both meaning big fish. The specific epithet griseus refers to the mottled (almost scarred) grey colour of the dolphin’s body.

Length is typically 10 feet (3 m), although animals have been recorded up to 12.5 feet (3.8 m). Like most dolphins, males are typically slightly larger than females. This species weighs 300-500 kg (660-1100 lbs), making it the largest species called “dolphin”, since orcas, pilot whales, etc., while actually dolphins, have no common name referring to them as such.
Population and distribution

It is found worldwide in temperate and tropical waters, usually in deep waters rather than close to land. As well as the tropical parts of the Indian, Pacific and Atlantic Oceans, Rissos are also found in the Persian Gulf, Mediterranean and Red Seas, though are absent from the Black Sea. Their preferred environment is just off the continental shelf on steep banks (with water depths varying from 400-1000m) with water temperature at least 10°C and preferably in excess of 15°C.

The population around the continental shelf of the United States has been recorded to be in excess of 60,000. In the Pacific a census recorded 175,000 individuals in eastern tropical waters and 85,000 in the west. No global estimate of population exists.
Human interaction

Risso’s dolphins generally do not approach boats. A notable exception was an individual named Pelorus Jack who accompanied boats in Admiralty Bay in New Zealand’s Marlborough Sounds for more than 20 years. Whaling of this species has never been particularly widespread, though operations off Sri Lanka may be significantly damaging the local population.[citation needed] Globally the species is recognised as abundant and safe.

Risso’s have been taken into capitivity successfully in the United States and Japan, though with nowhere near the regularity of bottlenose dolphins or orca. Hybrid Risso’s-bottlenose dolphins have been bred in captivity.
Strandings

At least one case report of strandings in the Goto Islands (Japan) has been associated with parasitic neuropathy of the VIIIth cranial nerve by a trematode in the genus Nasitrema . (See Morimitsu et al. 1992. J Wildl Dis 28:656-658).

There is a dolphin stranded in the River Clyde Glasgow, Scotland. Marine experts believe the dolphin was hit by seacraft out on the Clyde coast which distressed the animal causing it to swim up the Clyde to the Finnieston area of Glasgow.

Kogia simus, Dwarf sperm whale

Kogia simus

 Dwarf sperm whale

The dwarf sKogia simus, Dwarf sperm whaleperm whale (Kogia sima) is one of three species of whale in the sperm whale family. They are not often sighted at sea and most of our understanding of the creatures comes from the study of washed-up specimens.
Nowadays the dwarf sperm whale is generally classified as one of two species, along with the pygmy sperm whale, in the Kogiidae family and Kogia genus, however it was not until 1966 that the two species were regarded as separate, and even more recently Kogiidae was regarded as a subfamily (Kogiinae) of Physeteridae.
Physical description

The dwarf sperm whale is the smallest of all whales. It grows up to 2.7 m in length and 250 kg in weight – making it smaller than the bigger dolphins. The species makes slow, deliberate movements with little splash or blow and will usually lie motionless when at the sea’s surface. Consequently it can be observed only in very calm seas.

The dwarf sperm whale is physically very similar to, and has the same behavioural characteristics as, its cousin the pygmy sperm whale. Identification may be close to impossible at sea – however, the Dwarf is slightly smaller and has a considerably larger dorsal fin. The body is mainly bluish grey 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). These teeth have led to the species being described as the “rat porpoise” in the Lower Antilles.

Like the other Sperm Whales, the dwarf sperm whale has a spermaceti organ in its forehead. Like the pygmy sperm, 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 creatures but have occasionally been seen in small groups. They feed mainly on squid and crab.
Population and distribution

The dwarf sperm whale prefers deep water, but is still more coastal than the pygmy sperm. Its favorite habitat appears to be just off the continental shelf. In the Atlantic, strandings have been observed in Virginia, United States in the west and Spain in the east, and as far south as southern Brazil and the tip of Africa. In the Indian Ocean, specimens have been found on the south coast of Australia and on many places along the Indian Ocean’s northern coast – from South Africa right round to Indonesia. In the Pacific, the known range includes the Japanese coast and British Columbia. No global population estimates have been made. One survey estimated a population of about 11,000 in the eastern Pacific.
Human interaction

The dwarf sperm whale has been actively hunted by commercial whalers. Occasional harpoon kills are made by Indonesian and Japanese fishermen. As the dwarf sperm whale is more coastal than the pygmy, it may be more vulnerable to human interference such as fishing and pollution. No data exists at this time as to whether such activities are threatening the long-term survival of the species.

Lagenodelphis hosei, Fraser’s dolphin

Lagenodelphis hosei

 Fraser’s dolphin

Fraser’s Dolphin (LagenodelphLagenodelphis hosei, Fraser's dolphinis hosei) or Sarawak Dolphin is a cetacean in the family Delphinidae found in deep waters in the Pacific Ocean and to a lesser extent in the Indian and Atlantic Oceans.

The earliest known interaction between mankind and a Fraser’s Dolphin came on a beach in Sarawak, Borneo in 1895. Mr. Charles E. Hose found a skull there and donated it to the British Museum. The scientific specific name is given in his honour. The skull remained unstudied until 1956 when Francis Fraser examined the skull and concluded that it was similar to species in both the Lagenorhynchus and Delphinus genera but not the same as either. A new genus was created by simply merging these two names together.

It wasn’t until 1971 that the whole body of a Fraser’s Dolphin, as it was by then becoming known, was discovered. At that time washed-up specimens were found on Cocos Island in the eastern Pacific, in South Australia and in South Africa.
[edit] Physical description

Fraser Dolphins’ are about 1 m long and 20 kg weight at birth, growing to 2.75 m and 200 kg at adulthood. They have a stocky build, a small fin in relation to the size of the body, conspicously small flippers. The dorsal fin and beak are also insubstantial. The upper side is a grey-blue to grey-brown. A dirty cream coloured 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 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 areas of ocean.

Fraser 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”.

The species feeds on pelagic fish, squid and shrimp found some distance below the surface of the water (200–500 metres). Virtually no sunlight penetrates this depth, so feeding is carried out using echolocation alone.
Population and distribution

Though only accounted for relatively recently, the number of reported sightings has become substantial—indicating that the species may not be as rare as thought as recently as the 1980s. However the species is still not nearly as well understood as its more coastal cousins. No global population estimates exist.

The Dolphin is normally sighted in deep tropical waters; between 30° S and 20° N. The Eastern Pacific is the most reliable site for viewings. Groups of stranded dolphins have been found as far afield as France and Uruguay. However these are regarded as anomalous and possibly due to unusual oceanographic conditions, such as El Nino