Der Indusdelfin (Platanista minor) ist eine sehr seltene Zahnwalart, die im Indus und seinen Nebenflüssen endemisch ist. Die verbliebenen etwas mehr als 1000 Tiere leben in drei, durch Staudämme voneinander getrennten Populationen. Das heutige Verbreitungsgebiet erstreckt sich über 700 km und umfasst damit nur noch etwa 20 % des ursprünglichen Verbreitungsgebietes. 1970 wurde die Art in Pakistan unter Schutz gestellt.
Der Indusdelfin wird maximal 2,5 Meter lang und kann ein Gewicht von 90 kg erreichen. Weibchen sind größer und haben eine längere Schnauze. Das Kopfprofil ist durch die auffällige Melone steil und abgerundet. Auf der Melone findet sich ein länglicher, unebener Kamm, seitlich dessen hinteren Endes das längliche, schlitzartige Blasloch liegt. Die über den Mundwinkeln liegenden Augen sind kaum entwickelt und winzig. Die Schnauze ist gavialartig lang und sehr schlank. Der vordere, knollenartig verdickte Teil ist mit zahlreichen, länglichen und scharfen Zähnen besetzt. Das Genick der Tiere ist für Wale ungewöhnlich flexibel und beweglich. Der Rücken ist flach und breit. Auf dessen hinteren Abschnitt liegt die flache, dreieckige Finne, die in einem niedrigen Grat endet, der sich bis auf die breite Fluke erstreckt. Die Fluke ist hinten konkav und hat lange, spitze Enden. Die Flipper sind breit und paddelartig. Ihre Hinterkanten sind flach oder gewellt, so dass ein fingerartiger Eindruck entsteht.
Indusdelfine sind olivgelb, olivbraun, graubraun oder graublau gefärbt. Die Bauchseite ist heller, oft rosig. Jungtiere sind einheitlich grau gefärbt.
Der Indusdelfin lebt allein oder paarweise. Er schwimmt normalerweise langsam und springt selten. Sprünge sind jedoch durch das laute Platschen auffällig. Die Fluke ist dabei nur selten sichtbar. Tauchgänge dauern zwischen 30 Sekunden und mehreren Minuten. Die Echoortungsklicks, die er zur Orientierung und Nahrungssuche abgibt, hören sich über der Wasseroberfläche wie Niesen an. Oft schwimmt er auf einer Seite liegend. Gegenüber Menschen ist er scheu.
Der Indusdelfin wird auf der Roten Liste der IUCN als stark gefährdet ("endangered") gelistet. Die Gesamtpopulation wird auf um 1000 Individuen geschätzt. Der größte Teil der Population (ca. 70 %) lebt im Abschnitt des Indus zwischen dem Staudamm bei Sukkur in der pakistanischen Provinz Sindh und der Guddu Barrage, einem Staudamm im Norden der Provinz.
Der Indusdelfin galt ursprünglich als Unterart des Gangesdelfin, von dem er sich äußerlich nicht unterscheidet. Heute besteht keine Einigkeit über die Taxonomie: In der Datenbank Mammal Species of the World wird der Indusdelfin als eigenständige Art geführt, während zum Beispiel er auf der Roten Liste der IUCN und von der Society for Marine Mammalogy unter dem Namen Platanista gangetica minor als Unterart von Platanista gangetica geführt wird, welche nach dieser Einteilung auch den Gangesdelfin umfasst[1]. Taxonomische Kategorien wie Art und Unterart sind stets eine modellhafte Beschreibung von evolutionären Verwandtschaftsverhältnissen, weswegen es häufiger zu derartigen uneinheitlichen Klassifizierungen kommen kann.
Der Indusdelfin (Platanista minor) ist eine sehr seltene Zahnwalart, die im Indus und seinen Nebenflüssen endemisch ist. Die verbliebenen etwas mehr als 1000 Tiere leben in drei, durch Staudämme voneinander getrennten Populationen. Das heutige Verbreitungsgebiet erstreckt sich über 700 km und umfasst damit nur noch etwa 20 % des ursprünglichen Verbreitungsgebietes. 1970 wurde die Art in Pakistan unter Schutz gestellt.
The Indus river dolphin (Platanista minor), also known as the bhulan in Urdu and Sindhi, is a species of toothed whale in the family Platanistidae. It is endemic to the Indus River Basin of Pakistan and northwestern India. This dolphin was the first discovered side-swimming cetacean. It is patchily distributed in five small, sub-populations that are separated by irrigation barrages.[3]
From the 1970s until 1998, the Ganges River dolphin (Platanista gangetica) and the Indus dolphin were regarded as separate species; however, in 1998, their classification was changed from two separate species to subspecies of a single species. However, more recent studies support them being distinct species. It has been named as the national mammal of Pakistan, and the state aquatic animal of Punjab, India.
The Ganges river dolphin split from the Indus river dolphin during the Pleistocene, around 550,000 years ago.[4] This species and the Indus river dolphin, were initially classified as a single species, Platanista gangetica, but in the 1970s both were split into distinct species. However, in the 1990s, both species were again grouped as a single species. However, more recent studies of genes, divergence time, and skull structure support both being distinct species.[5] Alternative names for the Indus River Dolphin include the Indus blind dolphin, side-swimming dolphin, and bhulan.[6]
The Indus river dolphin presently only occurs in the Indus River system.[3] These dolphins occupied about 3,400 km of the Indus River and the tributaries attached to it in the past.[3] But today, its only found in one fifth of this previous range. Its effective range today has declined by 80% since 1870.[3] It no longer exists throughout the tributaries, and its home range is only 690 km of the river.[3][7] This dolphin prefers a freshwater habitat with a water depth greater than 1 meter and that have more than 700 meters squared of cross-sectional area. Today this species can only be found in the Indus River's main stem, along with a remnant population in the Beas River. A population can be found in the Harike Wetland located in Punjab, India.[8]
Since the two originally inhabited river systems – between the Sukkur and Guddu barrage in Pakistan's Sindh Province, and in the Punjab and Khyber Pakhtunkhwa Provinces – are not connected in any way, how they were colonized remains unknown. The river dolphins are unlikely to have travelled from one river to another through the sea route, since the two estuaries are very far apart. A possible explanation is that several north Indian rivers such as the Sutlej and Yamuna changed their channels in ancient times while retaining their dolphin populations.[9]
The Indus dolphin has the long, pointed nose characteristic of all river dolphins. The teeth are visible in both the upper and lower jaws even when the mouth is closed. The teeth of young animals are almost an inch long, thin and curved; however, as animals age the teeth undergo considerable changes and in mature adults become square, bony, flat disks. The snout thickens towards its end. The species does not have a crystalline eye lens, rendering it effectively blind, although it may still be able to detect the intensity and direction of light. Navigation and hunting are carried out using echolocation.
The body is a brownish color and stocky at the middle. The species has a small triangular lump in place of a dorsal fin. The flippers and tail are thin and large in relation to the body size, which is about 2-2.2 meters in males and 2.4–2.6 meters in females. The oldest recorded animal was a 28-year-old male 199 centimeters in length.[10] Mature adult females are larger than males. Sexual dimorphism is expressed after females reach about 150 cm; the female rostrum continues to grow after the male rostrum stops growing, eventually reaching approximately 20 cm longer. Calves have been observed between January and May and do not appear to stay with the mother for more than a few months. Gestation is thought to be approximately 9–10 months.
The species feeds on a variety of crustaceans and fish, including prawns, carp, catfish, gobies, etc.
The Indus river dolphin has been very adversely affected by human use of the river systems in the subcontinent. Entanglement in fishing nets can cause significant damage to local population numbers. Some individuals are still taken each year and their oil and meat used as a liniment, as an aphrodisiac and as bait for catfish. Irrigation has lowered water levels throughout their ranges. Poisoning of the water supply from industrial and agricultural chemicals may have also contributed to population decline. Perhaps the most significant issue is the building of dozens of dams along many rivers, causing the segregation of populations and a narrowed gene pool in which dolphins can breed. There are currently three sub-populations of Indus dolphins considered capable of long-term survival if protected.[3]
The Indus river dolphin is listed by the IUCN as endangered on their Red List of Threatened Species[11] and by the U.S. government National Marine Fisheries Service under the U.S. Endangered Species Act. It is the second most endangered cetacean in the world. As of 2017 it is estimated that there are only about 1,800 individuals remaining (up from 1,200 estimated in 2001).[12] A demonstrable increase in the main river population of the Indus subspecies between 1974 and 2008 may have been driven by permanent immigration from upstream tributaries, where the species no longer occurs.[13]Today, the species is only found between the Jinnah and Kotri barrages of the Indus.
There are many threats to their survival. Reckless and extensive fishing that reduces their prey availability is a large factor.[14] Also, they are sometimes accidentally entangled in the fishing nets which can cause fatalities.[15] Deforestation that occurs along the river basin is causing sedimentation which degrades the dolphin's habitat.[14] Another factor in their decline is the construction of cross-river structures such as dams and barrages. These are a problem because they cause more isolation in the already small sub-populations.[14] Lastly, human induced water pollution is a major threat factor. This pollution is usually in the form of either industrial and human waste, or agricultural run-off containing high amounts of chemical fertilizers and poisonous pesticides.[14]
Studies suggest that a better understanding of this species ecology is needed in order to develop good conservation plans. Regular monitoring is also a necessity to assess the population's status and factors causing its decline.[14] There are currently several organizations that are helping to conserve the Indus dolphin. The World Wildlife Fund (WWF) is involved in rescue missions and helping to reduce pollution in the river. A satellite tagging effort was begun in 2022.[16] In addition, WWF Pakistan is assisting in educating the public, and have arranged training courses for many institutions.
The species is protected under Appendix I of the Convention on the International Trade of Endangered Species which prohibits the commercial international trade of the species (including parts and derivatives).[3]
The Indus river dolphin (Platanista minor), also known as the bhulan in Urdu and Sindhi, is a species of toothed whale in the family Platanistidae. It is endemic to the Indus River Basin of Pakistan and northwestern India. This dolphin was the first discovered side-swimming cetacean. It is patchily distributed in five small, sub-populations that are separated by irrigation barrages.
From the 1970s until 1998, the Ganges River dolphin (Platanista gangetica) and the Indus dolphin were regarded as separate species; however, in 1998, their classification was changed from two separate species to subspecies of a single species. However, more recent studies support them being distinct species. It has been named as the national mammal of Pakistan, and the state aquatic animal of Punjab, India.
El delfín del Indo (Platanista minor), también conocido como bhulan o delfín ciego del Indo, es una especie de cetáceo odontoceto de la familia de los platanístidos[2] oriundo del río Indo, en Pakistán.
Idéntico en apariencia al delfín del Ganges, posee un largo hocico. Es completamente ciego al carecer de cristalino, se desplazan y cazan mediante la ecolocalización. Miden unos 2,5 m de longitud.
Reside primordialmente en el río Indo. La mayor parte de la población, menos de 600 ejemplares en total, habita en el curso bajo del río, entre las presas de Sukkur y Guddu. La presencia de varias presas impide el movimiento de los individuos y mantiene aisladas las poblaciones.
El delfín del Indo (Platanista minor), también conocido como bhulan o delfín ciego del Indo, es una especie de cetáceo odontoceto de la familia de los platanístidos oriundo del río Indo, en Pakistán.
Platanista minor
Le dauphin de l'Indus ou, plus rarement, plataniste de l'Indus et, localement, bhulan est selon les auteurs une espèce (Platanista minor) ou une sous-espèce (Platanista gangetica minor) de dauphin d'eau douce du genre Platanista.
Il possède un corps gris-brun d'une longueur moyenne de 2 mètres pour un poids d'environ 80 kg. Comme la plupart des dauphins d'eau douce, il possède un rostre long et étroit (pouvant mesurer jusqu'à 20 % de sa taille totale). Il est doté de larges nageoires pectorales mais ne possède pas d'aileron dorsal qui est remplacé par une simple bosse[1] ce qui lui permet de nager en travers dans des eaux peu profondes.
Fréquentant des eaux boueuses, il est quasiment aveugle, mais se sert de son écholocalisation pour trouver sa nourriture consistant en poissons et mollusques.
La femelle est plus grande que le mâle ; la gestation dure 11 mois et le delphineau mesure près d'un mètre à la naissance.
Comme son nom l'indique, cette espèce vit dans le bassin de l'Indus au Pakistan[2].
C'est une espèce menacée de disparition par l'industrialisation et la chasse (pour sa viande et son huile utilisée en cosmétique et en aphrodisiaque). Seul un millier d'individus subsistent et on leur pronostique à court terme une perte de diversité génétique. On le trouve rarement en groupes de plus de trois individus ; il semble par ailleurs migrer le long du fleuve au gré des saisons.
Platanista minor
Le dauphin de l'Indus ou, plus rarement, plataniste de l'Indus et, localement, bhulan est selon les auteurs une espèce (Platanista minor) ou une sous-espèce (Platanista gangetica minor) de dauphin d'eau douce du genre Platanista.
Il delfino dell'Indo (o Bhulan) (Platanista minor Owen, 1853) è un mammifero della famiglia dei Platanistidae endemico del fiume Indo, in Pakistan.
L'inquadramento tassonomico di questa specie è controverso e da alcuni è considerata una sottospecie di Platanista gangetica (P. gangetica minor)
Hanno il muso lungo e appuntito caratteristico di tutti i delfini di fiume. I denti sono visibili sia sulla mascella superiore che su quella inferiore anche quando la bocca è chiusa. I denti degli animali giovani, sottili e ricurvi, sono lunghi quasi due centimetri e mezzo, anche se con l'età tendono a subire sostanziali cambiamenti, divenendo, negli adulti, dei dischi piatti, squadrati ed ossei. L'estremità del muso si volge all'indietro all'estremità. La specie è priva della lente oculare del cristallino, cosa che la rende effettivamente cieca, sebbene possa ancora essere in grado di distinguere l'intensità e la direzione della luce. I movimenti e la caccia vengono effettuati grazie all'ecolocazione. Il corpo, di colore brunastro, si fa più robusto nel mezzo. La specie ha solamente una piccola massa triangolare al posto della pinna dorsale. Le natatoie e la coda sono sottili e grandi rispetto alle dimensioni del corpo, che sono di circa 2-2,2 metri nei maschi e 2,4-2,6 m nelle femmine. L'animale più vecchio registrato era un maschio di 28 anni di 199 centimetri di lunghezza. Le femmine adulte mature sono più grandi dei maschi. Il dimorfismo sessuale si spiega con il fatto che dopo che le femmine raggiungono circa 150 cm, il loro rostro continua a crescere, raggiungendo una lunghezza approssimativa di 20 cm, mentre quello dei maschi smette di crescere. Dei piccoli sono stati osservati tra gennaio e maggio e sembra che vivano con la madre solamente per pochi mesi. Si pensa che la gestazione sia approssimativamente di 9-10 mesi.
La specie si nutre di una grande varietà di gamberetti e pesci, tra cui carpe e pesci gatto. Si incontrano solitamente delfini solitari o in piccole aggregazioni, che non formano mai dei gruppi veri e propri.
Risiede principalmente nel fiume Indo, in Pakistan. Nel diciannovesimo secolo il suo areale era approssimativamente cinque volte più esteso di oggi, includendo anche affluenti dell'Indo, come il Sutlej, il Ravi, il Chenab e il Jhelum. La densità di popolazione più alta si ha nella provincia del Sind.
Un esauriente censimento della popolazione del delfino dell'Indo completato nel 2001 dal WWF-Pakistan ha concluso che oggi vivano approssimativamente 1100 individui.
Questa specie è stata molto danneggiate dall'uso che l'uomo ha fatto dei sistemi fluviali del subcontinente. Gli intrappolamenti nelle reti da pesca possono causare danni significativi al numero della popolazione locale. Alcuni individui vengono ancora cacciati ogni anno e il loro olio e la loro carne vengono usati come unguento, come afrodisiaco e come esca per i pesci gatto. L'irrigazione ha fatto abbassare il livello dell'acqua e anche l'avvelenamento delle acque causato dalle sostanze chimiche usate nell'industria e nell'agricoltura ha contribuito al declino della popolazione. Forse il danno più significativo è stato la costruzione di dighe che ha causato la frammentazione delle popolazioni e la diminuzione del pool genico. Attualmente esistono tre sottopopolazioni di delfino dell'Indo che, se protette, sarebbero capaci di una sopravvivenza a lungo termine.
Il delfino dell'Indo e classificato dalla IUCN Red List come in pericolo di estinzione.
La Zoological Society of London, in base a criteri di unicità evolutiva e di esiguità della popolazione, considera Platanista gangetica minor una delle 100 specie di mammiferi a maggiore rischio di estinzione.
Il delfino dell'Indo (o Bhulan) (Platanista minor Owen, 1853) è un mammifero della famiglia dei Platanistidae endemico del fiume Indo, in Pakistan.
