South Asian River Dolphin - Profile | Traits | Facts | Skull

(Last Updated On: April 15, 2021)

The South Asian river dolphin, scientific name Platanista gangetica is an endangered freshwater or river dolphin discovered within the area of the Indian subcontinent, which is cut up into two subspecies, the Ganges river dolphin (P. g. gangetica, ~3,500 people) and the Indus river dolphin (P. g. minor, ~1,500 people). In this article, I am going to talk about South Asian River Dolphin habitat, baby, eyes, facts, skull, pink, cute, etc.

The Ganges river dolphin is primarily discovered within the Ganges and Brahmaputra rivers and their tributaries in India, Bangladesh, and Nepal, whereas the Indus river dolphin is now discovered solely in the main channel of the Indus River in Pakistan and energetic channels linked to it between the Jinnah and Kotri barrages, and within the River Beas (a tributary of the Indus) in Punjab in India.

Geographic Range

Limited to southern Asia, Platanista gangetica inhabits the Ganges and Indus rivers and the numerous related tributaries and linked lakes. This species is restricted to freshwater.

There are two subspecies: Platanista gangetica gangetica, present in Eastern India, Nepal, and Bangladesh within the Ganges, Meghna, Karnaphuli, Bramaputra, and Hooghly river techniques, and Platanista gangetica minor, present in Pakistan within the Indus River system.

South Asian River Dolphin Description

The South Asian river dolphin has the long, pointed nostril attribute of all river dolphins. Their teeth are seen in each the higher and decrease jaws even when the mouth is closed.

The teeth of younger animals are nearly an inch long, skinny, and curved; nonetheless, as animals age, the teeth endure appreciable modifications, and in mature adults grow to be sq., bony, flat disks.

The snout thickens in direction of its end. Navigation and looking are carried out utilizing echolocation. They are distinctive amongst cetaceans in that they swim on their sides.

The body is a brownish coloration and stocky in the center. The species has solely a small, triangular lump within the place of a dorsal fin.

The flippers and tail are skinny and huge in relation to the body size, which is about 2-2.2 meters in males and a couple of.4–2.6 m in females. The oldest recorded animal was a 28-year-old male, 199 cm in size.

Mature females are bigger than males. Sexual dimorphism is expressed after females attain about 150 cm (59 in); the feminine rostrum continues to develop after the male rostrum stops rising, finally reaching roughly 20 cm (7.9 in) long.

Lifespan/Longevity

Very little is understood concerning the lifespan and longevity of Ganges River dolphins. Few specimens have been noticed for the whole thing of their lives, however, a handful of estimates exist.

The oldest male on record lived to be 28 years of age, whereas the oldest feminine reached 17.5 years of age. Based on crude estimates, dolphins reaching 18 to 22 years of age might not be unusual. Few profitable efforts have introduced Platanista gangetica people into captivity for study.

South Asian River Dolphin Physical Traits

The two subspecies of Ganges River dolphins are nearly equivalent in bodily look. They are readily recognized by their elongated snout, which might attain lengths of 20% of total body size.

Upon sexual maturity, females develop barely longer snouts than males. This attribute is helpful in figuring out sexually mature people. The beak is comparatively flat and turns into the widest on the tip.

They bend barely upward and might attain a size of 21 cm. On each of the top and decrease elements of the jaw they’ve long, sharp teeth, that are seen even when the mouth is closed.

On the higher jaw, there are between 26 and 39 teeth on all sides, and on the decrease jaw 26 to 35 teeth on all sides. The decrease teeth are sometimes longer than the teeth on the higher jaw. With age, the teeth finally are worn down and grow to be flat. Unlike different dolphins, Platanista gangetica lacks snout hairs.

Well designed for aquatic life, Ganges River dolphins have long flippers that may be as much as 18% of total body size. The tail fluke is kind of massive as properly, reaching 46 cm or roughly 1 / 4 of total body size.

The dorsal fin resembles a fleshy hump on its back and is often only a few centimeters in height. They are often a gray to brown coloration, however can also have pink bellies and darkish gray backs. Dorsal coloration is usually darker than ventral coloration.

The skull is very asymmetrical and has a distinctly steep brow and a longitudinal ridge. These river dolphins are distinctive in having long necks with unfused vertebrae. This makes them capable of flip their heads back and forth with great flexibility.

Ganges River dolphins are typically known as “blind river dolphins” since their eyes are extraordinarily tiny and lack a lens. These animals should not reliant on vision as a major sensory system, but the eye is believed to perform as a light detector.

Slightly bigger than the attention and positioned just under it are the exterior ears. The blowhole is longitudinally positioned, which is exclusive compared to the horizontally positioned blowholes in most different toothed whales.

Ganges River dolphins characteristically have a number of folds of pores and skin that kind a wattle. The actual performance or objective of this ornamentation is unknown.

Upon sexual maturity, females are typically bigger than males in general body size and snout size. Unofficial data have adult females measuring 400 cm, however, the average adult not often exceeds 300 cm in size. At delivery, younger average 70 cm in size. Typical adult weights are between 51 and 89 kg.

South Asian River Dolphin Eyes

The species lacks a crystalline eye lens and has advanced a flat cornea. The mixture of those traits makes the attention incapable of forming clear pictures on the retina and renders the dolphin successfully blind, however, the eye should still function as a light receptor.

The retina accommodates a densely packed receptor layer, a really skinny bipolar and ganglion cell layer, and a tiny optic nerve (with just a few hundred optic fibers) which are ample for the retina to behave as a light-gathering element.

Although its eye lacks a lens (this species can also be known as the “blind dolphin”), the dolphin nonetheless makes use of its eye to find itself. The species has a slit just like a blowhole on the top of the top, which acts as a nostril.

The dense pigmentation within the pores and skin overlying the attention prevents light from reaching the retina from any entrance apart from a pinhole sphincter-like construction. This construction is managed by a cone-shaped muscle layer that extends from the posterior eye orbit to the overlying eye pores and skin layer.

The sphincter-like construction is able to sense light and might be able to sense the route from the place the light was emitted. However, the muddy waters, or low light circumstances, that P. gangetica inhabits negate using the little vision that is still.

South Asian River Dolphin Habitat

Ganges River dolphins occupy freshwater river techniques in southern Asia. They inhabit the Ganges and Indus River techniques and their many tributaries, streams, and connecting lakes.

They are present in tributaries that run by the hills and lowlands in Nepal (roughly 250 meters above sea level) and typically in flood plains and areas of rivers with heavy currents.

These river dolphins want areas that create eddy countercurrents, akin to small islands, river bends, and convergent tributaries. Since these animals occupy an enormous space of river techniques, they’ll tolerate a large variance of temperatures; some as chilly 8 degrees Celsius to heat waters above 33 degrees Celsius (46.4F to 91.4F).

They inhabit depths from Three to 9 meters and should floor each jiffy for air. In the monsoon season, Ganges River dolphins domestically migrate to tributaries after which back to bigger river channels within the dry, winter season. They additionally transfer alongside the coast of the Bay of Bengal when monsoons flush freshwater out alongside the southeastern coast of India.

South Asian River Dolphin Vocalization

The Ganges subspecies reveals object-avoidance behavior in each of the constantly closely murky waters of its habitat and in clear water in captivity, suggesting it’s able to utilize echolocation successfully to navigate and forage for prey.

However, information is restricted on how extensively vocalization is used between people. This subspecies of river dolphin is able to perform whistles, however not often does so, suggesting that the whistle is a spontaneous sound and never a type of communication. The Ganges river dolphin most sometimes makes echolocation sounds akin to clicks, bursts, and twitters.

Produced pulse trains are related in wave kind and frequency to the echolocation patterns of the Amazon river dolphin. Both species recurrently produce frequencies that decrease by 15 kHz and the utmost frequency is believed to fall between 15 and 60 kHz.

Echolocation can also be used for inhabitants counts through the use of acoustic surveying. This technique remains to be being developed and isn’t closely used as a consequence of price and technical skill requirements. Given the dolphin’s blindness, it produces an ultrasonic sound that’s echoed off different fish and water species, permitting it to establish prey.

South Asian River Dolphin Behavior

Ganges River dolphins are solitary animals however they sometimes congregate in teams of three to 10 people. Groups of as many as 30 animals have been reported. Mothers and calves keep collectively till the infants are weaned.

Despite their largely solitary nature, these river dolphins are present in unfastened aggregations, particularly at tributary junctions the place prey congregate. Some take into account Ganges River dolphins semi-gregarious.

There are some indications of territoriality, as chasing behaviors in males have been noticed. Generally, these animals are shy in direction of people, even in captivity. Their elusive nature has made them troublesome topics to check.

Ganges River dolphins have a particular technique of swimming, in that they swim on their sides when submerged. At roughly a 10 degree angle, they swim a couple of centimeters from the underside, consistently nodding the top, permitting it to comb the underside looking for meals.

For unknown causes, most people swim on their right sides. Side swimming additionally positions their eye at an angle applicable to sensing light, maybe offering orientation for the animal whereas diving.

Their tails are all the time positioned higher than the top in aspect swimming, permitting them to swim in water as shallow as 30 cm. When the floor for air, they level out and swim laterally.

In captivity, measured swimming velocity reached 5.4 km/hr, but this might not be a consultant of possible speeds within the wild, the place habitats are more open. They have been recorded swimming upwards of 27 km/hr within the wild.

Captive animals swim and vocalize constantly over a 24-hour interval, with solely temporary interruptions lasting a couple of seconds. When swimming depth relaxed, for instance in drifting locomotion, the depth of vocalizations emitted additionally relaxed.

Dives are sometimes quick, the longest wild dive was Three minutes. Average dive instances within the wild are between 1 minute 10 seconds and 1 minute 40 seconds.

Dives in captivity are shorter than wild dive instances, with the longest being 1 minute and 35 seconds. In many cetaceans, myoglobin concentrations are typically high to deal with the stress of diving, however, as a consequence of their comparatively shallow river habitats and quick dive durations, myoglobin concentrations in heart and muscle tissues are significantly decrease.

South Asian River Dolphin Food Habits

Ganges River dolphins are the top predators of their river ecosystems. Side swimming and a versatile neck enable them to look river bottoms to fire up hiding prey.

Their formidable velocity and skill to swim in shallow water allow them to chase and herd faculties of fish. They feed on quite a lot of aquatic animals. Their bodily look demonstrates how properly outfitted they’re to catch fish and crustaceans.

They are strictly carnivorous, though some vegetation has been discovered of their stomachs, almost certainly on account of messy foraging within the river bed or leftover plant stays contained in the fish the dolphins have consumed.

Their teeth and long snouts are designed to catch and maintain fish. They have been noticed shaking prey of their jaws and manipulating it to be swallowed headfirst in order that the scales on the fish don’t transfer in opposition to the animal’s throat.

As these dolphins don’t use vision as a sensory system to catch prey, they depend on echolocation to seek out meals hidden within the mud and river backside. Once prey is situated, they seize it with their long snouts.

Diet

South Asian river dolphins depend on echolocation to seek out prey as a consequence of their poor eyesight. Their prolonged rostrum is advantageous in detecting hidden or hard-to-find prey objects. The prey is held of their jaws and swallowed. Their teeth are used as a clamp somewhat than a chewing mechanism.

The species feeds on quite a lot of shrimp and fish, together with carp and catfish. The Ganges subspecies might take birds and turtles. They are often encountered on their very own or in unfastened aggregations; the dolphins don’t kind tight interacting teams.

Predation

Other than people, there aren’t any identified natural predators of Ganges River dolphins. Humans have exploited these animals for oil, meat, and as bait for catching catfish. Otherwise, they’re sometimes thought-about the top predator of their river ecosystems.

South Asian River Dolphin Communication

Ganges River dolphins have poor vision. They lack lenses of their eyes, making it inconceivable for them to resolve pictures, they’re prone to solely be capable to detect the presence or absence of light.

Ganges River dolphins have extremely developed sonar techniques. They use pulse sounds not whistles to navigate. This permits them to understand objects, particularly prey, in murky water.

Over a 24-hour period, there may be near all the time a constant emission of sound, 87% of those sounds are clicked for echolocation, the remaining sounds are sounds utilized in communication. There has not been sufficient research to find out the importance is of those communicative sounds.

Lifecycle

Births might happen year-round, however seem concentrated between December to January and March to May. Females gestate on average as soon as every two years; gestation is regarded as roughly 9–10 months.

After around one year, juveniles are weaned they usually attain sexual maturity at about 10 years of age. During the monsoon, South Asian river dolphins are likely to migrate to tributaries of the principle river techniques.

Occasionally, people swim together with their beaks rising from the water, they usually might “breach”; leaping partly or utterly away from the water and landing on their sides.

South Asian River Dolphin Reproduction

Not a lot is understood about mating techniques in Ganges River dolphins. Further research has to be performed to offer information concerning their mating behavior. They breed year-round.

Difficulty finding out these species can partly be attributed to the environmental circumstances of their habitat because of the monsoon season. In addition, the political and socio-economic state of the realm the place these dolphins are discovered just isn’t conducive to analysis.

Breeding in Platanista gangetica happens year-round, as does birthing. Most births are from October to March, with a peak in December and January, previous to the start of the dry season.

Gestation is often about 10 months, however, may be from Eight to 12 months. Ganges river dolphins bear a single offspring from 70 to 90 cm long. Weaning can start as early as 2 months or as late as 12 months, the typical time to weaning is at 9 months old.

Once offspring have been weaned, they disperse and grow to be unbiased. Males and females sometimes attain sexual maturity at 10 years of age, though growth continues into their 20’s.

Ecosystem Roles

Ganges River dolphins are the top predators of their river ecosystems. They are necessary for controlling and maintaining healthy fish and crustacean populations, their major sources of meals. Unfortunately, these river dolphins are experiencing the antagonistic results of human environmental impacts and are extremely endangered.

Conservation Status

Ganges River dolphins are among the many most endangered of all cetaceans. With rising human populations in Southern Asia, the natural habitat of Ganges River dolphins has been extensively modified and degraded.

Agricultural and industrial discharges are polluting the river techniques by which these dolphins stay and feed. Insure populations, the buildup of heavy metals and organochlorides is posing severe health dangers to the animals.

In addition, dangerously high ranges of arsenic within the water is a severe health risk to each animal utilizing the water system, together with Ganges River dolphins. Human modifications to river techniques are additionally impacting the habitat of the dolphins.

Over fifty dams have an effect on populations of Ganges River dolphins, reducing populations off from each other. Dams have precipitated the gene swimming pools of Ganges River dolphins to shrink, which may pose detrimental results in future generations.

Some engineering efforts are underway to assemble channels around dams for aquatic wildlife, together with dolphins. Ganges River dolphins have gotten more and more restricted to a smaller range.

In Pakistan, a couple of hundred river dolphins are restricted to roughly 1200 square kilometers of water. Many native peoples regard these dolphins as a source of meat, oil, and bait. Hunting has actually impacted the numbers of dolphins within the Ganges and Indus river techniques.

South Asian River Dolphin – Profile | Traits | Facts | Skull | Eyes