Bottlenose dolphins are present in most oceans and seas of the world and adapt quickly to several types of habitat.

Their thermoregulation capacity allows them to live in waters ranging from 10 to 32 degrees Celsius, which includes temperate, tropical and subtropical areas of the Pacific, Atlantic, Indian Ocean, as well as the Mediterranean Sea and the Black Sea between Europe and Asia. The regions that avoid are the polar zones, but some individuals move through the north of Europe, whose waters have low temperatures.

In the Pacific, their distribution range is from northern Japan to Australia and from southern California to Chile in the eastern Pacific Ocean including all the vast area in the middle.

In the Atlantic ocean, they dwell from Nova Scotia to Patagonia in the West and from Norway to South Africa in the East including all the eastern coast of the United States, and the Gulf of Mexico.

Bottlenose dolphin habitat includes bays, open waters, coastal areas, lagoons, estuaries, tidal areas and shallow areas. They even venture occasionally into some rivers.

The other bottlenose species, the Indo-Pacific bottlenose dolphin, is also distributed in tropical and subtropical areas in specific regions of the ocean. This dolphin inhabits from western South Africa to Japan, including eastern and western Australia and places such as the Red Sea, Persian Gulf, Solomon Islands and the Indo-Malay archipelago.

The Indo-Pacific dolphin lives near the coasts of continental shelves, at depths of less than 300 meters and around oceanic islands. It frequently visits estuaries and coral reefs where fish banks thrive, and a significant amount of cephalopods live. Therefore it tolerates salt water and brackish waters.

An ecological niche is a role or way of life that an organism takes within its habitat and how it adapts to meet its basic needs to survive and proliferate, through a set of conditions, resources, and interactions with others.

Two organisms can not have the same niche, as they would compete for the same resources, which would cause only the strongest to survive, leading its opponent to extinction. In nature, although there are some species whose niches overlap, they have different options that make them easier to satisfy their daily requirements.

In this sense, the niche of Orcas is quite variable. The extensive distribution of this species makes that its populations have different cultures that have evolved according to their environment. Some even think that new unidentified subspecies are wandering in the oceans right now.

The niche of these cetaceans differs more clearly in their diet. For example, North Pacific killer whales that live south of Alaska, Washington, and British Columbia and are known as residents rely on fish and squid. In contrast, orcas called transients and whose range of distribution overlaps with residents, but without interbreeding, have a diet that is based primarily on marine mammals.

The interesting thing about killer whales is that they are not limited by salinity, temperature or depth since they have the capacity to move through waters of different latitudes, the open sea or reach coastal areas with depths of only a few meters.

The five ecotypes of Antarctic killer whales and three of Pacific killer whales differ considerably in diet habits, habitat, behavior, and social structure. Therefore their niche entirely depends on the ecotype.

INFORMATION AND CHARACTERISTICS.

Although the common and scientific name of this toothed cetacean refers to the white color of its snout, they may or may not have the beak of this color.

The white-beaked dolphin is the largest member of the genus Lagenorhynchus, and it was one of the first dolphins of this genus to be scientifically recognized, back in 1846.

Order: Cetacea
Family: Delphinidae
Genus: Lagenorhynchus

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

Morphology.
It has a sturdy body, a short and thick beak and a narrow tail. It has a big and sickle-shaped dorsal fin just in the middle of its body.

Weight and size.
Adult individuals measure between 2.3 and 3.1 meters in length and weigh 180 to 354 kilograms. Males are slightly larger than females.

Skin Coloration.
It has a black or dark gray dorsal area. The sides usually have lighter stripes with different shades of light gray almost white. Its beak may exhibit a whitish color, but it can also be gray and even black.

Distinctive characteristics.
It has a white patch that starts just behind the dorsal fin and ends before the tail flukes.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

The white-beaked dolphin inhabits the waters of the North Atlantic Ocean. In the western part of this ocean it dwells from the Strait of Davis to the south of Cape Cod (Massachusetts, United States) passing through the center and the west of Greenland; In the east of the ocean is distributed from Iceland to Portugal but in the north reaching as east as the Scandinavian peninsula. Its locations include the Barents Sea, the Baltic Sea, Ireland, Canada, the Irish Sea and the United Kingdom. It also resides in the west of the Mediterranean Sea.

It inhabits the cold subpolar waters of its distribution zone, in the continental shelf, along with the edge of this and in coastal waters; Mainly in waters whose depth does not exceed 200 meters.

WHAT DO THEY EAT? DIET AND EATING HABITS.

It feeds on a large variety of mesopelagic fish mainly those that group in schools, like the capelin, haddock, hake, herring and cod. It also consumes crustaceans and cephalopods (octopus and squid), like most dolphins.

This species performs hunting techniques cooperatively on the surface of the ocean. It sometimes associates with humpback whales (Megaptera novaeangliae), Fin whales (Balaenoptera physalus) and other dolphins, including those of the species Tursiops truncatus (bottlenose dolphin).

HOW DO THEY BEHAVE? BEHAVIOR

The White-beaked dolphins create social groups composed of 5 to 50 individuals (generally less than 30), but they occasionally form larger groups of up to 1,500 dolphins. There is little information on the social structure of this species, but the separation by age and sex can occur. They sometimes mix and associate with large species like fin whales and humpback whales, and other small cetaceans, especially in the feeding areas (Reeves et al. 2002). These gregarious dolphins often perform acrobatic jumps on the surface and frequently approach ships to ride the bow waves.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

The white-beaked dolphin reaches sexual maturity when it is between 7 and 13 years old or when they grow to a length of 2.4-2.5 meters. The gestation period lasts about 11 or 12 months. Subsequently, a single offspring is born in the summer (months of May to September) measuring about 1.1-1.2 meters long.

Additional information on the reproduction of this species is so far unknown.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: “Least Concern.”

This species has been and still is hunted in the waters of the Faroe Islands, Iceland, Norway and Greenland, and even in Canada off the coast of Newfoundland, to obtain its oil and meat. Also, they are affected by the contamination of their habitats with heavy metals and organochlorines.

It is under protection by the ASCOBANS (Agreement on the Conservation of Small Cetaceans in the Baltic, North East Atlantic, Irish and North Seas) and in the Red List of the International Union for the Conservation of Nature, it appears as a species with a conservation status of “Least Concern.”

References

Jefferson, Webber, Pitman. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press, 2015. Page 282.

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 1255.

http://www.cms.int/reports/small_cetaceans/data/l_albirostris/l_albirostris.htm

http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/whitebeakeddolphin.htm

Globicephala macrorhynchus

INFORMATION AND CHARACTERISTICS.

The Short-finned pilot whale is the name of the second largest species of dolphin, only surpassed by the orca (Orcinus orca).

Order: Cetacea
Family: Delphinidae
Genus: Globicephala

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

This species is commonly called whale, without being one, because of its large size and its behavior similar to that of whales. It has the following characteristics:

Morphology.
From the body of the Short-finned pilot whale stands out a bulbous head, big and prominent that in the male is more notorious and in some old individuals hangs slightly above the mouth. The beak is missing from the head, and instead, it has a short snout. It has short pectoral fins and a sickle-shaped dorsal fin located near the head.

Weight and size.
Males are longer and heavier than females, so sexual dimorphism is present in the species. It measures about 5.5 meters while the opposite sex reaches a length of 3.7 meters. The weight of adults is 1,000-3,000 kilograms.

Skin Coloration.
Its skin has a dark gray or black color in most parts which contrast with a light gray or white stripes on the chest and neck. In the bottom of the chin, there is a light patch with anchor shape. Above the eye, it has a stripe running down the dorsum and extending backward from the dorsal fin. A white or light gray patch with a saddle shape is behind its dorsal fin.

Distinctive characteristics.
It is very similar to the Long-finned pilot whale and is often confused. The difference between them lies in the length of the pectoral flippers, which in this case are smaller.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

It inhabits tropical, subtropical and warm waters of the world. Native to the Atlantic, Pacific, and Indian oceans, it does not venture beyond the latitudes 50° North and 40° South. Many individuals dwell in areas north of the Atlantic Ocean, the Western Pacific and the southern hemisphere.

There are populations from the Gulf of Alaska to Guatemala, from Eastern Europe to Africa, the Sea of ​​Japan, the Red Sea, Hawaii and the Strait of Gibraltar.

It is common in deep offshore areas near the continental shelf or deep underwater canyons. Sometimes it reaches coastal regions. It inhabits at waters with depths of 600-1,000 meters.

WHAT DO THEY EAT? DIET AND EATING HABITS.

The primary food of the Short-finned pilot whale is not precisely fish, but cephalopods, mostly octopus, and squid. The 45 kilograms of food they eat per day also contain some small fish species and probably other marine mammals. Surprisingly, this cetacean sometimes chases sperm whales and other dolphins, although there is not conclusive evidence that is hunting them, it is thought to consume warm-blooded animals.

Their favorite feeding species are the following:
– Cape Hope squid (Loligo reynaudii).
– “Wonderful Lamp” squid (Lycoteuthis).
– European flying squid (Todarodes sagittatus).
– Squid (Eucleoteuthis luminosa).
– California market squid (Loligo opalescens).
– Neon flying squid (Ommastrephes bartrami).
– Giant Pacific Octopus (Enteroctopus dofleini).
– Glass squid of the genus Cranchia.

This dolphin looks for food at dawn and dusk. When it is time, it does very deep dives, of more than 600 meters, and can travel more than 1 kilometer of distance between its starting point and the final zone of feeding.

In this regard, the availability of prey occasionally makes them perform coastal movements and change their habits. Their dives relate with the ascension of their usual benthic prey to the upper water column. Another clear example: when the squid comes to spawn near the coasts, the calderón follows the trail and also resides there for a short time.

HOW DO THEY BEHAVE? BEHAVIOR.

It is a social animal that gathers in pods composed of 10-60 members and sometimes hundreds and usually is not alone. The base of its society is the group of females with their offspring, and from them, the non-breeding females are considered a “database” that stores information about the pod.

In any case, the bonds between individuals are very close and intense, similar to that of the long-finned pilot whales (Globicephala melas). Cooperation is essential in the group, and even a female can provide care for a calf that is not her own.

It is mainly nocturnal and relegates its rest and its travels to the day. While there is no sun, it dives to hunt and socialize with its mates.

It always travels from one place to another, but there is no information about the migration patterns that follows. The short-finned pilot whale goes to other locations depending on the movements of its prey or the changes in water temperature.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

The Short-finned pilot whale is polygamous. There is one male for every eight mature females which facilitates the mating opportunity to the former, but also the females mate with multiple males throughout their life. The interval between each delivery is 5-8 years.

The female matures between 7 and 12 years of age and the male between 7 and 17 years. However, the average maturation age of female and male is 9 and 14.6 years, respectively. The existence of a defined breeding season is unknown, but they can reproduce at any time of the year although most births occur during the spring, autumn and winter months.

Males join different pods and manage to mate with a female. Once it is pregnant, it moves to the group of mothers with calves and waits for 15 months the birth of its offspring. The calf receives care from its mother and other females of the pod and is weaned at about two years old.

During its lifetime, a female has 4 or 5 offspring, until she is about 40 years old. The last offspring of a female can feed with breast milk from the mother for up to 15 years!

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: “Data Deficient.”

In Japan, they eat several dishes prepared with Short-finned pilot whales.

The Short-finned pilot whale is in danger as a result of bycatch with gillnets, trawls and longlines, collisions with boats of any type, massive strandings and loud sounds that disturb their environment.

It is necessary to emphasize that humans have much responsibility for the deaths of these cetaceans. In Japan, the large number of catches are because the Short-finned pilot whale, like other cetaceans, is consumed in various Asian dishes.

This dolphin has a conservation status of “Data Deficient” on the Red List od the International Union for the Conservation of Nature. The Pacific Offshore Cetacean Take Reduction Plan implemented by the NMFS (National Marine Fisheries Service) regulates the use of fishing devices to reduce the numbers of deaths caused by the incidental catch of these dolphins.

References

http://www.iucnredlist.org/details/9249/0

http://www.cms.int/reports/small_cetaceans/data/G_macrorhynchus/g_macrorhynchus.htm

http://animaldiversity.org/accounts/Globicephala_macrorhynchus/

]]> https://www.dolphins-world.com/pantropical-spotted-dolphin/ Thu, 27 Apr 2017 05:27:30 +0000 http://www.dolphins-world.com/?p=92 Pantropical Spotted Dolphin

(Stenella attenuata)

INFORMATION AND CHARACTERISTICS.

The pantropical spotted dolphin is a toothed cetacean typical of temperate and tropical waters. John Gray, a British zoologist, was the first scientist to describe it in 1846.

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

Morphology.
Like other members of the genus Stenella, this species has a thin, small and hydrodynamic body. It has a long and thin snout separated from the melon by a fold. It has a narrow, curved and sickle-shaped dorsal fin.

Weight and size.
The male of the tropical spotted dolphin is larger than the female. It has an average weight of 120 kilograms and a length of approximately 2.5 meters.

Order: Cetacea
Family: Delphinidae
Genus: Stenella

Skin Coloration.
The upper body has a dark gray color sprinkled with light spots that often overlap. The lower part of the jaw, neck, and belly, has a lighter color sprayed with dark spots. The sides have three tones of gray that blend into each other and a dark gray stripe from the eyes to the base of the snout.

Distinctive characteristics.
There is not much to add since the main way to identify the species is to observe its thin body and the skin coloration pattern, characterized by multiple light and dark spots. It has similar resemblance with other species of the genus Stenella. Therefore, the color patterns are paramount to distinguish them from the others.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

It dwells in tropical, warm and temperate waters of the Atlantic, Pacific and the Indian Ocean between latitudes 40° north and 40° south. In the eastern Pacific Ocean lives from Mexico to Peru. In the south, it thrives in waters of Argentina, New South Wales and the Province of Cape of Good Hope. There are larger populations in the southern areas of their distribution range.

The Persian Gulf, the Red Sea, the Gulf of Mexico, the South China Sea, the Bay of Bengal, the Arabian Sea, and the East China Sea are also habitats of the pantropical spotted dolphin.

It rarely approaches to areas near the coast. On the contrary, it is usually 163 kilometers away from the shore in waters whose depths are less than 50 meters, and their temperature exceeds 25° C. Those who live in the Atlantic Ocean are almost always offshore, but in the eastern Pacific, they venture to come close to the coast.

The pantropical spotted dolphin consumes about 56 species of fish and 36 species of cephalopods.

WHAT DO THEY EAT? DIET AND EATING HABITS.

The pantropical spotted dolphin feeds on epipelagic and mesopelagic fish as well as on crustaceans and cephalopods. Specifically, it consumes about 56 species of fish and 36 species of cephalopods, with a greater predominance of lanternfish (myctophids). In some regions, it feeds on flying fish and crab larvae.

The feeding time begins at night when the prey reaches the surface of the ocean, and the dolphin detects, follows and chases them to feed on these animals. Probably in the eastern Pacific Ocean, this dolphin feeds opportunistically.

Females breastfeeding consume more fish than squid because the former are richer in calcium, phosphorus, and protein.

HOW DO THEY BEHAVE? BEHAVIOR

It is an extremely gregarious species that associates with other dolphins of the same species, but also with other species of animals. Near the coasts, the pods have a few hundred spotted dolphins, but in high seas, the pods can have up to thousands of individuals. A society of these dolphins usually has groups of:
a) Mothers and their offspring,
b) Adult males and
c) young dolphins.

The dolphins of this species that live in Japanese waters are a unique case. After weaning, at about the age of 2 years, the little ones join groups along with other very young individuals. The arrival of sexual maturity coincides with its return to the original pod.

Their associations are designed to facilitate various activities. It has been seen interacting with other oceanic dolphins and even with yellowfin tuna (Thunnus albacares).

It is very fast, and it can reach speeds of 22 to 28 kilometers per hour. It jumps very high off the water or very low at great speed; this is common in the young dolphins.

It makes seasonal migrations in some parts of the eastern Pacific and off the coast of Japan. In the summer, the individuals that inhabit near this country travel towards the north and in winter they move to the south; One of its objectives is to visit areas with abundant prey.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

This dolphin mates any time of the year. Most scientists think that it is a polygamous dolphin and that females give birth every 2 or 3 years. The females reach sexual maturity between 9 and 11 years of age, while males reach maturity between 12 and 15 years.

The gestation period is approximately 11 months, and there is a higher incidence of births during the spring and fall. Only one offspring is born, but there is a register of the born of twins and another case of a 35-year-old pregnant female.

The duration of the breastfeeding period extends for 1 or 2 years after birth. However, the mother can continue breastfeeding its offspring even when she is pregnant again. At six months of age, the calf begins trying solid foods.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Some populations of this species have been reduced or disappeared.

In its natural habitat, the pantropical spotted dolphin is predated by killer whales and sharks. Once again, the human activities burst into the natural life of a species and cause more problems than benefits.

The eastern Pacific has been a killing area since fishers are aware of the association of the yellowfin tuna and the pantropical spotted dolphin. The fisherman does not want the Dolphins only the tuna, but they capture them together after following the trail of the cetacean to reach its target. During the process, the dolphin is under stress and get killed during the catch. The consequence: some populations have been reduced or disappeared.

In Japan, the Philippines, and the Solomon Islands, the problem is the intentional catch since its meat is used for human consumption or as bait. Other threats include bycatch and pollution of their habitat.

The indisputable reduction of the populations of this species triggered the alarms. In 1979, the Inter-American Tropical Tuna Commission (IATTC) launched a program to conserve dolphins and fortunately has had positive results. The Southwest Fisheries Science Center of the National Oceanic and Atmospheric Administration (NOAA) has launched two programs for dolphin conservation:

– The Dolphin Energetics Program.
It involves tuna fishing strategies that do not include the use of dolphins.

-The Dolphin Safe Program.
It determines the reasons for the recovery of dolphin populations in the eastern tropical Pacific Ocean.

References

Jefferson, Webber, Pitman. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press, 2015. Page 246.

http://www.iucnredlist.org/details/20729/0

http://www.cms.int/reports/small_cetaceans/data/S_attenuata/s_attenuata.htm

http://www.science.smith.edu/msi/pdf/683_Stenella_attenuata.pdf

http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=51

DOLPHINS ARE CETACEANS

All dolphins belong to the cetacean infraorder which also includes whales, dolphins, and porpoises.

The Cetacea infraorder is broken down into two parvorders. The first is the Mysticeti, which is made up of Baleen Whales, a group that captures prey by straining water through a series of baleen plates in their mouths which act as filters to collect the food.

ODONTOCETI PARVORDER, THE TOOTHED CETACEANS.

The second parvorder in the Cetacea infraorder is the Odontoceti; a group made up of toothed whales which have several families and superfamilies.

The first family is the Ziphiidae, which is composed entirely of big toothed whales like the beaked whales, a group of deep divers, rarely seen by humans.

The second family in the Odontoceti parvorder is the Physeteridae, which includes only the Sperm Whale,

The third is the Kogiidae which includes the Pygmy Sperm Whale, and Dwarf Sperm Whale.

The fourth family is the Monodontidae family, which includes the Beluga Whale and the Narwhal.

The Superfamily Inioidea includes the four families of river dolphins, and all the species that dwell in freshwater belong to this group.

The Stenidae family, includes the Rough-Toothed Dolphin, Pantropical Spotted Dolphin, Striped Dolphin, Spinner Dolphin, Short, Tucuxi, Guiana Dolphin, Chinese White Dolphin.

The Delphinidae family is made up of oceanic dolphins including:

The last family in the parvorder is the Phocoenidae family, which includes several species of porpoises like the Harbor Porpoise, Spectacled Porpoise, Black Porpoise, Black Finless Porpoise, Dall’s Porpoise, True’s Porpoise, Finless Porpoise, and Cochito Porpoise.

The name Dolphin comes from the word womb, and it is believed to be the Greek saying for fish with a womb.

DOLPHIN OR WHALE?

The largest dolphin species is the Orca, which is commonly known as the Killer Whale. These dolphins can be over 31 feet long when fully grown, a size which has provided them with the colloquial name of whales although they are dolphins.

There are all types of dolphins, some live in shallow waters near the coasts, but other prefer the high seas. Some fancy warm tropical waters while some species inhabit circumpolar regions. There are great differences among the species of dolphins, and that is why there are various genus and families.

In 2011, scientists discovered a new dolphin species in Big City Harbor around Australia. The novel dolphin got the colloquial name of Burrunan Dolphin and is believed to inhabit only two areas at this time. There are about 100 of them in Port Phillip Bay around Melbourne and about 50 more of them in the coastal lakes of Gippsland which is about 100 miles away.

The type of dolphin you will see in a given area depends on environmental factors such as food availability and the temperature. The time of year also is a factor due to the migrational patterns of most dolphins. Studies also indicate that there are differences among the species of dolphins regarding their skull size and form, variations that may lead to future taxonomical changes.

Young dolphins are called calves, and the female adults are cows. The male adults are bulls, and a group of them is called a pod.

Perhaps the most popular of all dolphins is the Bottlenose Dolphin; This is the species you often see in books, movies, and when you visit an aquarium. They are intelligent, easy to train, and they are more likely to approach humans in the wild than other species.

River Dolphins live in freshwater, and they inhabit some of these systems in South America and Asia. They are smaller than most oceanic dolphins, with an average size of about 8 feet when fully mature. They can be various colors including brown, gray, or pink.

The Roughed Tooth Dolphin, as some other species, is harder to spot out there in the ocean because they prefer waters with great depths. They can weigh around 350 pounds and measure about 8 ½ feet long. They have a small head and feature a long snout, lacking the crease on the melon that other dolphins have separating the beak from this organ.

The square-shaped head of the Risso Dolphin is a telling sign of what species you are seeing. They don’t have any teeth in the upper jaw, but they have several pegs-like teeth on the bottom jaw.

The Striped Dolphin gets its name from the blue and white stripes on its body. This species is believed to have the highest population in the world as well as the biggest overall distribution of that population. If you want to be impressed by acrobatics, check out this Dolphin.

The Common Dolphin was very respected in the early cultures. Researchers have found items from the Ancient Greek and Roman times picturing this cetacean.

The Dusky Dolphins tend to live in waters cooler than the temperatures preferred by other species of dolphins. They can be found in coastal regions as well performing astonishing leaps out of the water.

The Killer Whale is the most remarkable dolphin due to its size and strength. They can take down seals effortlessly which is important due to the significant volume of food that they need to consume on a daily basis.

The Pilot Whale can weigh up to 5,000 pounds and be up to 24 feet long being the second largest dolphin only after the Killer whale. They are believed to be the most social of the dolphin species.

References

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009.

Annalisa Berta. Whales, Dolphins, and Porpoises: A Natural History and Species Guide. University of Chicago Press, 2015.

Mark Simmonds. Whales and Dolphins of the World. New Holland Publishers, 2007.

(Sousa chinensis)

INFORMATION AND CHARACTERISTICS.

The Chinese white dolphin is a variety of the Indo-Pacific Humpbacked Dolphin, although some consider it a subspecies of the latter. It is a species of dolphin characterized by the pink color of the skin that some individuals may have. The first time it was seen dates back to the seventeenth century.

Two types of the Indo-Pacific Humpbacked Dolphin are known (Sousa chinensis and Sousa plumbea), although the taxonomy of Sousa chinensis is not yet clear as some scientists consider it a variety but others a subspecies. If the latter, its scientific name is Sousa chinensis chinensis.

Order: Cetacea
Family: Delphinidae
Genus: Sousa

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

The physical characteristics of the individuals of this species vary slightly according to the geographic region in which they live. For example, male specimens from the coasts of some areas have sexual dimorphism that other populations do not have.

Morphology.
It has a hydrodynamic body with a long, slender beak and a dorsal fin with a fat hump. Dolphins inhabiting eastern waters have a short dorsal fin whose broad base descends gradually over the dorsum. In contrast, individuals from western territories have a shorter and curved dorsal fin. The hump represents between 5 and 15 percent of its total length.

Size and weight.
It is a small dolphin; its length is between 2 and 2.8 meters. Its weight is between 150 and 200 kilograms.

Skin Coloration.
Perhaps, if it were not for the genetics, the Indo-Pacific Humpbacked Dolphin could not be recognized because of the color variability depending on the geographic region it inhabits. The adult specimens of the Chinese coasts have a pinkish appearance thanks to the blood vessels underneath, not because the skin has that color. In contrast, young individuals are gray.

Distinctive characteristics.
The main distinctive feature of the Chinese white dolphin is the hump on the dorsal fin and the pink color that many specimens present on the skin.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

It is distributed only in waters of the Indian and Pacific Ocean, from northern Australia to eastern China as well as in the Indo-Malayan archipelago, the Bay of Bengal and the Gulf of Thailand. The plumbea type is found on the coasts of the Indian Ocean while the chinensis is mainly in the Pacific.

They prefer to inhabit warm and temperate waters with temperatures above 15° C and an average depth of 20 meters. They live on or near open coasts, bays, estuaries, mangroves, sandbanks, reefs, coastal lagoons, and river mouths.

Chinese white dolphin – Sousa chinensis chinensis

WHAT DO THEY EAT? DIET AND EATING HABITS.

This dolphin prefers coastal fishes and those who live in reefs, littorals, and estuaries. Their prey includes cephalopods and crustaceans on few occasions.

It searches for opportunistic food in shallow waters, near the bottom of the ocean. If the tide is high, it ventures to areas with abundant food. In several areas of Australia, it has been seen following boats that catch fish and shrimp, to feed on discarded animals.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

Females reach sexual maturity at 9-10 years of age and males later, as they reach sexual maturity between 12 and 13 years.

The reproduction season is during the months of spring and summer although it can extend until the autumn. There is little information about the reproductive habits of this dolphin and much less about its courtship methods. Studies and observations indicate that this species has as its primary reproductive strategy searching for a partner to mate.

+ Gestation period: 10 to 12 months.

After a gestation period of ten to twelve months, the female gives birth to a single offspring measuring 1 meter in length that is the object of dedicated maternal care even after weaning, which occurs when the calf is about two years old. However, oddly, the maternal care does not take place in individuals living on the coasts of South Africa (Plumbea type) and Hong Kong.

HOW DO THEY BEHAVE? BEHAVIOR

The Chinese white dolphin shows a behavior slightly less social than other species because it has been seen several times swimming alone. This does not mean that they do not form pods, but these usually have less than ten members and occasionally equal to or larger than 25 individuals. In the same way, the relationships between members are not close except fo those of mothers with their offspring.

This species can stay more than 4 minutes underwater without surfacing. Sometimes it jumps out of the water and hits the surface with its flippers, but do not perform jumps and stunts frequently. These dolphins usually avoid boats unless they are fishing boats. In such cases, they can be seen next to other species of dolphins and even other animals like whales and gulls.

It communicates by whistles and squeals, and to a lesser extent by clicks. On the other hand, it is considered a migratory animal that travels more than 120 kilometers away from home. This occurs mainly in summer in regions close to the African continent (Plumbea type)

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: Near Threatened.

Sharks are the only known predators of this dolphin, although some think that they are also victims of killer whales (Orcinus orca), there are still no reliable reports on this fact.

Its main threats are related to anthropogenic activities that also endanger the lives of other dolphins. They are:

– The intentional catch for their meat and oil.

– Bycatch with gillnets.

– Habitat contamination.

– The decrease in the number of fish they feed on and fragmentation of the food chain.

– Coastal development that degrades its habitat (urbanization).

Because of the above, populations have declined drastically. It has a conservation status as “Near Threatened” on the Red List of the International Union for the Conservation of Nature.

References

http://www.bioone.org/doi/abs/10.1644/1545-1410(2001)655%3C0001:SC%3E2.0.CO;2

http://www.iucnredlist.org/details/20424/0

http://www.cms.int/reports/small_cetaceans/data/S_chinensis/s_chinensis.htm

Jefferson, Webber, Pitman. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press, 2015. Page 227.

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 576.

There is a lot of information that anyone interested in these animals should appreciate. There are plenty of great facts about them that you will learn when you get done reading this! Some are basic, others entertaining and many are simply amazing.1. Dolphins are odontocete cetaceans. The order Cetacea includes a group of mammals fully adapted to life in the ocean, and the suborder Odontoceti includes those with teeth.

2. The closest relatives of dolphins are whales and porpoises. All are members of the order Cetacea.

3. Dolphins are mammals; warm-blooded animals which give birth to live offspring and feed them with breast milk from the mother.

4. They do not have hair on the skin. Only a small accumulation of thin hair near the spiracle and in some other places. Only the Boto, Amazon River Dolphin, has a small amount of hair that they keep as an adult.

5. Dolphins are the only mammals that give birth to its offspring delivering the tail first instead of the head.

6. Like whales, manatees, seals, walruses and porpoises, they are mammals that live permanently in an aquatic environment.

7. Apparently, dolphins sleep resting one side of the brain at a time.
Thanks to its bone structure and its ability to hold air in the lungs for a long time, dolphins can rest underwater. However, they need to breathe regularly. Therefore, some degree of awareness is necessary, and one side of the brain remain active, while the other part rests.

8. Dolphins can communicate with each other by emitting a variety of sounds.

9. Dolphins do not have a good sense of smell.

10. Dolphins can swim at a speed of up to 25 miles per hour for a long time; This is about three times faster than the fastest humans in the world.

11. Dolphins inhabit all seas of the world.

12. Most species live in salt water, but some dwell in fresh or brackish waters.

13. All dolphins are carnivores.

14. There are about 100 teeth in the mouth of a dolphin, but the amount varies among species. However, they use the teeth to grab their prey, but they don’t chew it. All food is swallowed whole.

15. Dolphins can hear a frequency range ten times broader than that of a human being.

16. Dolphins are mostly larger than porpoises. However, some species of dolphins are the smallest cetaceans.

17. Mothers breastfeed calves for 2 or 3 years.

18. The lower limbs of dolphins are vestigial legs because millions of years ago they could walk on land.

19. There are about 43 species of dolphins. But the number keeps changing because of new discoveries and new taxonomic classifications.

20. There have been cases of attacks on humans, but they are very rare. Even though dolphins are usually very mild tempered, they can be aggressive.

21. At birth, calves weigh approximately 10 kilos and measure around one meter. This weight increases up to 7 times during the first year of life.

22. Many individuals have been seen making jumps in front of the ships and following the bow waves.

23. The teeth of dolphins work as a kind of antenna to pick up the sounds bounced back during echolocation.

24. Dolphins enjoy socializing and playing. They have been seen playing with small objects and with other dolphins. They play with seaweed or with other members of the pod. Sometimes, they will tease other living creatures in the water.

25. They are social animals and can live in groups called pods that can have hundreds of members or even join with other groups creating superpods with thousands of individuals.

26. The favorite foods of many species of dolphins are fish, octopus, and squid.

27. The gestation period in most species lasts between 10 and 12 months.

28. The Killer Whale (Orcinus orca) is the largest dolphin. It can measure up to 30 feet in length.

29. Dolphins detect prey and objects using their echolocation, that is, by interpreting the echo of sound waves bounced back by the target.

30. They have very delicate skin, which can easily be injured.

31. Dolphins have an organ called melon in the head that emits the sound waves used for echolocation.

32. The dolphin’s brain is similar in size to that of humans.
Their brains are 4-5 times larger than those of other animals of similar size.

33. Dolphins can recognize themselves in the mirrors which mean that they are self-aware, an indicator of intelligence.

34. Dolphins’ eyes can move separately from each other.

35. Bycatch is one of the main threats to the survival of dolphins.

36. Their main natural predators are sharks and ironically, orcas.

37. The Amazon River Dolphin or Boto is the largest dolphin that dwells in freshwater. They can be up to 10 feet long.

38. The Amazon river dolphins (Inia geoffrensis) can swim backward. So far, researchers unknown the exact reason for this behavior, but it is presumed to be related to searching food.

39. Dolphins have two stomachs just like cows. The first one stores the food and the second is where digestion takes place.

40. Some dolphin species can submerge up to 1,000 feet.

41. The dorsal fin on each dolphin is unique, and it can be used to identify them from each other.

42. The average lifespan of dolphins is around 17 years. However, some species in the wild live about 50 years.

43. Some dolphins need to breathe every 20 seconds, but others need to do it every 30 minutes.

44. The bonds between the members of a pod are very tight. They have been observed helping sick, elderly, and injured peers.

45. Dolphins can see well in the water due to the way their retina collects the light.

46. The brain of dolphins is the second largest ratio between size compared to its body size; only behind humans.

47. It is possible for a mature dolphin to eat up to 30 pounds of fish per day.

48. Some dolphins can leap up to twenty feet in the air.

49. Dolphins often use a hunting technique consisting in surrounding a school of fish, so they make a tight group. Then they will take turns going through the center of the accumulation to feed.

50. Global warming continues to be a problem for dolphins as it has reduced their food supply significantly.

51. Dolphins can migrate looking for food and reach parts of the ocean where the temperatures are right for them. Not all species of dolphins migrate.

52. Dolphins perform several feeding strategies to capture prey. Most involve cooperation among the pod members.

53. The smallest dolphins are about 4 feet long with the longest being 30 feet long. They can weigh from 90 pounds to more than 11 tons.

54. The flukes are the two parts of the tail of a dolphin.

55. All dolphins have a blowhole at the top where they breathe.

56. Dolphins have a great healing process even when they have deep wounds such as those that are the result of shark bites. Experts haven’t been able to determine how this is possible for dolphins when other mammals would die from a hemorrhage.

57. Dolphins are incredibly intelligent creatures, known for their ability to recognize themselves in mirrors and communicate with each other using distinct whistles. Learn more about this fascinating fact of the day.

Striped Dolphin Jumping

Image Courtesy of: U.S. National Oceanic and Atmospheric Administration

//www.youtube.com/watch?v=KVxYZQodoi8