63-730: Platanista gangetica Platanista minor South Asian river dolphins are toothed whales in the genus Platanista , which inhabit the waterways of the Indian subcontinent . They were historically considered to be one species ( P. gangetica ) with the Ganges river dolphin and the Indus river dolphin being subspecies ( P. g. gangetica and P. g. minor respectively). Genetic and morphological evidence led to their being described as separate species in 2021. The Ganges and Indus river dolphins are estimated to have diverged 550,000 years ago. They are
126-421: A family of cetaceans noted as being one of the least-known groups of mammals because of their deep-sea habitat, reclusive behavior and apparent low abundance. Only three or four of the 24 existing species are reasonably well-known. Baird's beaked whales and Cuvier's beaked whales were subject to commercial exploitation, off the coast of Japan , while the northern bottlenose whale was extensively hunted in
189-793: A Cuvier's beaked whale making a dive that lasted 222 minutes, another mammalian record. Deep-diving mammals face a number of challenges related to extended breath-holding and hydrostatic pressure. Cetaceans and pinnipeds that prolong apnea must optimize the size and use of their oxygen stores, and they must deal with the accumulation of lactic acid due to anaerobic metabolism. Beaked whales have several anatomical adaptations to deep diving: large spleens , livers, and body shape. Most cetaceans have small spleens. However, beaked whales have much larger spleens than delphinids, and may have larger livers, as well. These anatomical traits, which are important for filtering blood, could be adaptations to deep diving. Another notable anatomical adaptation among beaked whales
252-476: A deep dive and must pass vertically through varying received sound levels. Since the whale has limited remaining oxygen supplies at the end of a long dive, it probably has limited abilities to display any normal sound avoidance behavior. Instead, the whale must continue to swim toward the surface to replenish its oxygen stores. Avoiding sonar inevitably requires a change in behavior or surfacing pattern. Therefore, sonar in close proximity to groups of beaked whales has
315-473: A diversity of cochlea shapes, though Platanista was unusual in that it developed flatter spirals with larger gaps between them. During the middle Miocene, the ancestor of Platanista entered the Indo-Gangetic Plain , then covered by inland seas , and remained there when sea levels dropped in the late Neogene and its environment converted to freshwater. River dolphins likely traveled from
378-513: A large fossil ziphiid sample was discovered off the South African coast, confirming the extant ziphiid diversity might just be a remnant of a higher past diversity. After studying numerous fossil skulls off the shore of Iberia and South Africa, researchers discovered the absence of functional maxillary teeth in all South African fossil ziphiids, which is evidence that suction feeding had already developed in several beaked whale lineages during
441-476: A loose network of social partners with no obvious long-term associations. In contrast to females, some male northern bottlenose whales have been repeatedly recorded together over several years, and possibly form long-term associations. Studies of Blainville's beaked whales have revealed groups usually consist of a number of females, calves, and/or juvenile animals. These whales are assumed to live in "harem-like" groups, where several females and young are accompanied by
504-423: A recent study, gouge marks in the sea floor were interpreted to be a result of feeding activities by beaked whales. To understand the hunting and foraging behavior of beaked whales, researchers used sound and orientation recording devices on two species: Cuvier's beaked whale ( Ziphius cavirostris ) and Blainville's beaked whale ( Mesoplodon densirostris ). These whales hunt by echolocation in deep water (where
567-492: A reported maximum group size of 20 individuals, with the average ranging from 2.5 to 3.5 individuals. Berardius species and Longman's beaked whales ( Indopacetus pacificus ) are found in larger groups of up to 100 individuals. Not much information is available about group composition of beaked whales. Only three species have been studied in any detail: northern bottlenose whales, Blainville's beaked whales, and Baird's beaked whales. Female northern bottlenose whales appear to form
630-597: A single male. Baird's beaked whales are known to occur in multiple male groups, and in large groups consisting of adult animals of both sexes. Arnoux's beaked whales have also been observed to form large pods of up to 47 individuals off the Southern Ocean off the coast of Kemp Land, Antarctica. For many years, most beaked whale species were insulated from anthropogenic impacts because of their remote habitat. However, now several issues of concern include: A major conservation concern for beaked whales (family Ziphiidae)
693-510: A year. They eat their first solid food within a couple months. South Asian river dolphins reach sexual maturity at around ten years, though males may not reach their adult size until 20 years. Growth layers in the teeth suggest South Asian river dolphins can live up to 30 years. As of 2022, the IUCN Red List of mammals lists both South Asian river dolphins as endangered . Two assessments in 2014 and 2015 estimated populations of 3,500 for
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#1732783824634756-412: Is a slight depression in the body wall that allows them to hold their pectoral flippers tightly against their bodies for increased streamlining. However, they are not invulnerable to the effects of diving so deep and so often. Cascadia Research shows that the deeper the whales dive, the less often they dive per day, cutting their efforts by at least 40%. The challenges of deep diving are also overcome by
819-671: Is known about reproduction in these river dolphins. Courtship and mating behaviour for the Ganges species has been documented from March to May, when the water level is lower, and involves multiple males chasing one female and ends with one of the males earning the right to mate. Calves are born around a year later. Births in the Ganges river dolphin appear to be most frequent between December and January and between March and May. For Indus river dolphins, newborns are most commonly seen between April and May. Indus river dolphins calves are around 70 cm (28 in) long at birth and may nurse for up to
882-419: Is not always followed, however. Animals have been observed spending more than an hour at or near the surface breathing. Beaked whales are often seen surfacing synchronously, but asynchronous surfacing has also been observed. In March 2014, a study by Cascadia Research revealed that Cuvier's beaked whales were recorded to dive at least 2992 m in depth, a mammalian record. Another study, published in 2020, reported
945-450: Is the presence of a 'beak', somewhat similar to many dolphins . Other distinctive features include a pair of converging grooves under the throat, and the absence of a notch in the tail fluke. Although Shepherd's beaked whale is an exception, most species have only one or two pairs of teeth, and even these do not erupt in females (other than in the genus Berardius ). Beaked whale species are often sexually dimorphic – one or
1008-521: Is they appear to be vulnerable to modern sonar operations, which arises from recent strandings that temporally and physically coincide with naval sonar exercises. Mid-frequency active sonar (MFAS), developed in the 1950s for submarine detection, is thought to induce panic when experienced by whales at depth. This raises their heart-rates, forcing them to attempt to rapidly ascend toward the surface in search of air. This artificially-induced rapid ascent can cause decompression . Post mortem examinations of
1071-719: The Azores and the Canary Islands , and even off the coasts of Hawaii. Very little is known about the life history of beaked whales. The oldest recorded age is 84 years for a male Baird's beaked whale and 54 years for a female. For all other beaked whale species studied, the oldest recorded age is between 27 and 39 years. Sexual maturity is reached between seven and 15 years of age in Baird's beaked whales and northern bottlenose whales. Gestation varies greatly between species, lasting 17 months for Baird's beaked whales and 12 months for
1134-503: The Ganges River basin to the Indus via stream capture within the last five million years. The split between the two species is estimated to have occurred around 550,000 years ago based on mitochondrial DNA. South Asian river dolphins are stocky with broad, squared-off pectoral fins ; elongated, slender rostrums (snouts); and tiny triangular dorsal fins . Their neck joints give them great flexibility. Unusual among cetaceans,
1197-791: The Himalayan foothills to the Ganges Delta , across the countries of Nepal , India and Bangladesh . It is unknown if they are present in Bhutan . Outflows of freshwater into the Bay of Bengal have allowed them to swim along the coast, and there is at least one record of an individual entering the Budhabalanga River , around 300 km (190 mi) southwest of the Ganges Delta. This species has maintained much of its range since
1260-455: The IUCN as "lower risk, conservation dependent": Arnoux's and Baird's beaked whales, and the northern and southern bottlenose whales . The status of the remaining species is unknown, preventing classification. Beaked whales live very short lives in captivity when compared to other cetaceans such as common bottlenose dolphins and short-finned pilot whales, most surviving only a few days out of
1323-410: The blowhole is slit-shaped. The finger bones can also be seen through the flippers. South Asian river dolphins possess some features that are " primitive " for a cetacean, such as a cecum connected to the gut and air sacs near the blowhole. The testes of the males are located closer to the underside than in marine dolphins and descend more. Their skin ranges from grey to greyish-brown in colour, though
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#17327838246341386-509: The melon and protrude forward over the rostrum. These likely help them focus their echolocation signals in their riverine environment. The Ganges species also has a protrusion near the frontal suture , which distinguishes it from the Indus species. The teeth of South Asian river dolphins are curved and longer in the front, where they remain exposed when the jaws are closed. Indus dolphins have more teeth than Ganges dolphins, averaging 33.2 teeth in
1449-494: The melon , which help direct their echolocation signals. These dolphins prey mainly on fish and shrimp and hunt them throughout the water column . They are active through the day and are sighted in small groups. Both species are listed as endangered by the IUCN Red List of mammals. Major threats include dams, barrages , fishing nets, and both chemical and acoustic pollution. South Asian river dolphins were traditionally considered to be one species, Platanista gangetica , with
1512-562: The national aquatic animals of India and Pakistan respectively. Platanista gangetica Too Many Requests If you report this error to the Wikimedia System Administrators, please include the details below. Request from 172.68.168.236 via cp1112 cp1112, Varnish XID 952860947 Upstream caches: cp1112 int Error: 429, Too Many Requests at Thu, 28 Nov 2024 08:50:24 GMT Beaked whale See text Beaked whales ( systematic name Ziphiidae ) are
1575-581: The 19th century but has disappeared from some northern and western rivers and waterways. The Indus river dolphin mainly lives in the Indus River of Pakistan , with three subpopulations between the Chashma , Taunsa , Guddu , and Sukkur barrages . Two other populations exist south of Sukkur and in the Beas River of India. In the 19th century, this species was reported to have occurred throughout
1638-572: The Ganges and Indus River populations being subspecies ( P. g. gangetica and P. g. minor , respectively). Heinrich Julius Lebeck named the Ganges river dolphin Delphinus gangeticus in 1801, while Johann Georg Wagler coined the genus name Platanista in 1830, a Latin word derived from the Greek "platanistēs", which may be related to the Greek words platē ("oar") or platē ("flat, broad"). This name
1701-403: The Ganges river dolphin and 1,500 for the Indus river dolphin. The Ganges species appears to be decreasing, while the Indus species may be increasing. The habitat of these river dolphins intersects with some of the most densely populated areas, leading to intense competition for water and resources. The creation of dams and barrages in the Indus River system have heavily fragmented the range of
1764-878: The Indus River system, from the Indus River Delta north to Kalabagh just south of the Himalayas, including all the main tributaries. The Indus river dolphin is reported to have disappeared between the Jinnah and Chashma barrages after 2001. South Asian river dolphins inhabit major river channels during the dry season and travel to smaller tributaries for the monsoon . They are most commonly found in stream pools , meanders , and confluences , and around river islands and shoals , which produce relatively stable waters. They can be found in pools over 30 m (98 ft) deep, but usually dwell in shallower water. South Asian river dolphins appear to be active throughout
1827-490: The Indus river dolphin, leading to a population decline of 80% since the 19th century. Around 50 such structures have been built in the historical range of the Ganges species. Fragmentation of populations makes these dolphins more vulnerable to inbreeding. The heavy extraction of water in these dense populations also puts the dolphins at risk. River dolphins accumulate high amounts of persistent organic pollutants , pesticides , and heavy metals in their system due to being at
1890-470: The Miocene. Researchers also found fossil ziphiids with robust skulls, signaling that tusks were used for male-male interactions (speculated with extant beaked whales). Beaked whales are deep divers with extreme dive profiles. They regularly dive deeper than 500 m (1,600 ft) to echolocate for food, and these deep dives are often followed by multiple shallower dives less than 500 m. This pattern
1953-404: The absence of statistical analyses; by the late 1990s, the two populations were again considered to be two subspecies of a single species. A 2014 mitochondrial DNA study found insufficient differences to support their classification as separate species. However, a 2021 study reanalyzed the two populations and found significant genetic divergence and major differences in skull structure; this led to
South Asian river dolphin - Misplaced Pages Continue
2016-469: The conclusion that the two were indeed distinct species. South Asian river dolphins are the only surviving members of the family Platanistidae and the superfamily Platanistoidea. They are not closely related to other river dolphins of the families Lipotidae , Pontoporiidae , and Iniidae , which all independently adapted to freshwater habitats. The following cladogram is based on Gatesy and colleagues (2012) and McGowen and colleagues (2020); and shows
2079-1043: The day. Living in flowing waters, they swim almost constantly with only brief periods of sleep, which add up to seven hours per day. They swim on their sides when in shallow water. River dolphins generally surface with the rostrum, head, and dorsal fin breaking the water and rarely breach or raise the tail fluke, though surface activity can vary based on age, distance from shore and time of day. Diving may last as long as eight minutes among adults and subadults; dives of newborns and juveniles are not as long. River dolphins are typically seen alone or in groups of up to 10 individuals, though enough natural resources may attract up to 30 dolphins. Individuals do not appear to have strong social bonds, outside of mothers and calves. Living in shallow river environments with acoustic obstacles, these dolphins echolocate using repetitive clicks spaced 10 to 100 milliseconds apart. Their clicks are about one octave below those of oceanic toothed whales of comparable size, meaning that they provide less information about
2142-677: The earliest of which date back to the late Oligocene ( c. 25 million years ago). The number of species peaked around the early Miocene ( c. 19 million years ago) and declined afterward. Examples of ancient platanistids include the genera Otekaikea and Waipatia and the species Awamokoa tokarahi of late Oligocene New Zealand, the family Allodelphinidae of early Miocene North Pacific, and Notocetus vanbenedeni and Aondelphis talen of early Miocene Patagonia. Platanistidae fossils have been found in Miocene deposits in Europe and North America. Fossil Platanistoidea showed
2205-476: The exchange of lung gas with blood, likely minimizing the uptake of nitrogen by tissues. The throats of all beaked whales have a bilaterally paired set of grooves that are associated with their unique feeding mechanism, suction feeding. Instead of capturing prey with their teeth, beaked whales suck it into their oral cavity. Suction is aided by the throat grooves, which stretch and expand to accommodate food. Their tongues can move very freely. By suddenly retracting
2268-446: The eye to control access to the retina and prevent light scattering , similar to a pinhole . The ears are adapted to hearing low frequencies, having a short, flattened cochlea with widely spaced spirals. South Asian river dolphins inhabit the northern waterways of the Indian subcontinent . Ganges river dolphins live in the Ganges, Brahmaputra , Meghna , Karnaphuli , and Sangu rivers and their tributaries . Their range extends from
2331-400: The ice edges at both the north and south poles, to the equator in all the oceans. Specific ranges vary greatly by species, though beaked whales typically inhabit offshore waters that are at least 300 m deep. Beaked whales are known to congregate in deep waters off the edge of continental shelves, and bottom features, such as seamounts , canyons , escarpments , and oceanic islands, including
2394-436: The inner ear, gas embolism can cause hemorrhages, leading to disorientation or vestibular dysfunction. Breath-holding divers, like beaked whales, can develop decompression-related problems (the "bends") when they return to the surface after deep dives. This is a possible hypothesis for the mass strandings of pelagic beaked whales associated with sonar-related activities. To illustrate, a diving beaked whale may be surfacing from
2457-542: The location of an object, but the dolphins' maxillary crests likely compensate by providing greater directional sensitivity. Vocalisations used for communication include bursts and twitterings. River dolphins feed mainly on fish and shrimp. In one meta study , around 46% of prey items were found to be bottom-dwelling species, while 31% were near the surface, and 23% occupied the middle of the column. The most frequently taken prey are bagrid catfish , barbs , glass perches , spiny eels , gobies , and prawns . When hunting at
2520-435: The majority of their prey is located) between about 200 and 1,885 m (656 and 6,184 ft) and usually catch about 30 prey per dive. Cuvier's beaked whales must forage on average at 1,070 m (3,510 ft) for 58 minutes and Blainville's beaked whales typically forage at 835 m (2,740 ft) deep for an average of 47 minutes. The family Ziphiidae is one of the most widespread families of cetaceans, ranging from
2583-405: The male's teeth are actually a secondary sexual characteristic , similar to the antlers of male deer . Each species' teeth have a characteristically unique shape. In some cases, these teeth even hinder feeding; in the strap-toothed whale , for example, the teeth curve over the upper jaw, effectively limiting the gape to a few centimeters. Females are presumed to select mates based on the shape of
South Asian river dolphin - Misplaced Pages Continue
2646-422: The most damage. In 2019, a review of evidence on the mass strandings of beaked whale linked to naval exercises where sonar was used was published. It concluded that the effects of mid-frequency active sonar are strongest on Cuvier's beaked whales but vary among individuals or populations, and the strength of their response may depend on whether the individuals had prior exposure to sonar. The report considered that
2709-488: The most plausible explanation of the symptoms of decompression sickness such as gas embolism found in stranded whales to be the whales' response to sonar. It noted that no more mass strandings had occurred in the Canary Islands once naval exercises where sonar was used were banned there, and recommended that the ban be extended to other areas where mass strandings continue to occur. Four species are classified by
2772-611: The northern bottlenose whale. No data is available on their reproductive rates. Determining group size for beaked whales is difficult, due to their inconspicuous surfacing behavior. Groups of beaked whales, defined as all individuals found in the same location at the same time, have been reported as ranging from one to 100 individuals. Nevertheless, some populations' group size has been estimated from repeated observations. For example, northern and southern bottlenose whales ( H. ampullatus and H. planifrons ), Cuvier's beaked whales, and Blainville's beaked whales ( Mesoplodon densirostris ) have
2835-541: The northern part of the North Atlantic in the late 19th and early 20th centuries. Reports emerged in late 2020 of the possible discovery of a new beaked whale species off the coast of Mexico , the taxonomy of which had not been determined as of December 2020 . Beaked whales are moderate in size, ranging from 4 to 13 metres (13 to 43 ft) and weighing from 1 to 15 tonnes (0.98 to 14.76 long tons; 1.1 to 16.5 short tons). Their key distinguishing feature
2898-630: The ocean. The longest time period for a beaked whale living in captivity was 25 days. Alexander and Nicholas, two male beaked whales—their species unknown, though they were thought to be either Hubbs' beaked whale or Blainville's beaked whale —had become stranded in California on 24 August 1989. They were taken to Marine World California . Both of the whales would die of pneumonia ; Nicholas died on 8 September and Alexander died 10 days later. A handful of other beaked whales have been briefly kept in captivity. A juvenile female Cuvier's beaked whale
2961-481: The only living members of the family Platanistidae and the superfamily Platanistoidea. Fossils of ancient relatives date to the late Oligocene . South Asian river dolphins are small but stocky cetaceans with long snouts or rostra , broad flippers, and small dorsal fins. They have several unusual features. Living in murky river waters, they have eyes that are tiny and lensless; the dolphins rely instead on echolocation for navigation. The skull has large crests over
3024-472: The other sex is significantly larger. The adult males often possess a large bulging forehead, some to an extreme feature. However, aside from dentition and size, very few morphological differences exist between male and female beaked whales. Individual species are very difficult to identify in the wild, since body form varies little from one species to another. The observer must rely on often subtle differences in size, color, forehead shape, and beak length. In
3087-545: The potential to cause hemorrhaging or to disorient the animal, eventually leading to a stranding. Current research reveals two species of beaked whales are most affected by sonar: Cuvier's ( Z. cavirostris ) and Blainville's ( M. densirostris ) beaked whales. These animals have been reported as stranding in correlation with military exercises in Greece, the Bahamas, Madeira, and the Canary Islands. The livers of these animals had
3150-642: The relationship of South Asian river dolphins to other living toothed whale families: Sperm whales (Physeteridae) [REDACTED] Dwarf sperm whales (Kogiidae) [REDACTED] South Asian river dolphins (Platanistidae) [REDACTED] Beaked whales (Ziphiidae) [REDACTED] Pontoporiidae [REDACTED] Iniidae [REDACTED] Oceanic dolphins (Delphinidae) [REDACTED] Porpoises (Phocoenidae) [REDACTED] Belugas , narwhals (Monodontidae) [REDACTED] Several fossil species have been classified under Platanistoidea,
3213-817: The rostrum and surrounding areas may have some pinkish colouration. The Indus species tends to be more brownish. In one study sampling 46 Ganges river dolphins, the maximum length and weight recorded were 267 cm (8.76 ft) and 108 kg (238 lb). For the Indus species, the maximum length and weight were 241 cm (7.91 ft) and 120 kg (260 lb) (80 individuals sampled). Female Ganges dolphins are generally longer than Indus dolphins of both sexes, while male Ganges dolphins are shorter than Indus dolphins of both sexes. Indus dolphins tend to be proportionally heavier than Ganges dolphins, independent of sex. South Asian river dolphin skulls have unusual features. The maxilla (fixed upper jawbone) has pneumatic extensions or "crests" on each side which curve around
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#17327838246343276-672: The second-largest family of cetaceans (after the dolphins ). They were one of the first groups to diverge from the ancestral lineage. The earliest known beaked whale fossils date to the Miocene , about 15 million years ago. As many as 26 genera antedate humans. These include ancestors of giant beaked whales ( Berardius ), such as Microberardius , and ancestors of Cuvier's beaked whale ( Ziphius ); they had many relatives, such as Caviziphius , Archaeoziphius , and Izikoziphius . They were probably preyed upon by predatory whales and sharks , including Otodus megalodon . Recently,
3339-465: The skull, the expansion of the premaxillary process can be a key feature to identification. The blubber of these whales is almost entirely (94%) composed of wax ester , a unique characteristic of this family. Beaked whales are unique among toothed whales in that most species have only one pair of teeth. The teeth are tusk-like, but are only visible in males, which are presumed to use these teeth in combat for females for reproductive rights. In females,
3402-910: The states they inhabit. They can be found in numerous protected areas, including ones established specifically for them, such as the Indus Dolphin Reserve in Pakistan and the Vikramshila Gangetic Dolphin Sanctuary in India. International trade is prohibited by the listing of the South Asian river dolphins on Appendix I of the Convention on International Trade in Endangered Species . The Ganges and Indus river dolphins are considered to be
3465-416: The stranded whales in concurrence with naval exercises have reported the presence of hemorrhaging near the ears or gas and fat emboli, which could have a deleterious impact on beaked whales that is analogous to decompression sickness in humans. Gas and fat emboli have been shown to cause nervous and cardiovascular system dysfunction, respiratory distress, pain, and disorientation in both humans and animals. In
3528-461: The surface, dolphins listen for the movements of schooling fish which are then herded with spins, side-swimming, and lobtailing . Echolocation signals are not frequently used at the surface, since many fish at this level can hear ultrasound. At the mid-surface level, the dolphins use more echolocation clicks to find prey hidden in clutter and vegetation as far as 20 m (66 ft) away. They flush out bottom-dwelling prey by digging around. Little
3591-488: The teeth do not develop and remain hidden in the gum tissues. In December 2008, researchers from the Marine Mammal Institute at Oregon State University completed a DNA tree of 13 of 15 known species of Mesoplodon beaked whales (excluding the spade-toothed whale , which was then only known from a skeletal specimen and a few stranded specimens). Among the results of this study was the conclusion that
3654-468: The teeth, because the different species are otherwise quite similar in appearance. The social structure is not well known, but sightings of single males accompanying multiple females suggest a polygynous mating system, which would considerably limit the number of males a female can choose. Beaked whales comprise at least 22 species. Several species have been described only in the last two decades. Six genera have been identified. The beaked whales are
3717-405: The tongue and distending the gular (throat) floor, pressure immediately drops within the mouth, sucking the prey in with the water. Dietary information is available from stomach contents analyses of stranded beaked whales and from whaling operations. Their preferred diet is primarily deep-water squid, but also benthic and benthopelagic fish and some crustaceans, mostly taken near the sea floor. In
3780-540: The top of their riverine food web . Hence, they are seen as bioindicators for the health of river systems. Fishermen compete with these animals for fish of certain sizes. Dolphins captured in fishing nets are usually accidental , but dolphin oil is sought after as a fish lure, and thus fishermen may be motivated to kill caught dolphins. Being nearly blind and relying on echolocation for navigation, river dolphins are also negatively affected by noise pollution from boats. South Asian river dolphins are protected by law in all
3843-405: The unique diving physiology of beaked whales. Oxygen storage during dives is mostly achieved by blood hemoglobin and muscle myoglobin. While the whale is diving, its heart rate slows and blood flow changes. This physiological dive response ensures oxygen-sensitive tissues maintain a supply of oxygen, while those tissues tolerant to hypoxia receive less blood flow. Additionally, lung collapse obviates
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#17327838246343906-399: The upper jaw and the 32.9 in the lower jaw, as compared to 28.4 in the upper jaw and 29.4 in the lower. Living in murky waters, South Asian river dolphins are nearly blind, their tiny eyes having flattened corneas and no lens . The retina —which connects to a reduced optic nerve —does not form images but instead merely discerns light. The animal relies on a sphincter -like muscle around
3969-597: Was first given to the Ganges dolphin by Pliny the Elder in Naturalis Historia back in 77 CE . In 1853, Richard Owen described a specimen from the Indus and considered it to be the same species as the Ganges river dolphin, but a smaller form. Based on differences in skull and vertebrae structure, blood proteins, and lipids , scientists declared them to be separate species in the 1970s. The results of these studies were criticized for their small sample sizes and
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