| Bolivian river dolphin | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | Iniidae |
| Genus: | Inia |
| Species: | I. boliviensis |
| Binomial name | |
| Inia boliviensis d'Orbigny, 1834 | |
The Bolivian river dolphin (Inia boliviensis) is a species of the genus Inia .
Bolivian river dolphins were discovered by the Western world in 1832 by French researcher Alcide d'Orbigny. [2] The Bolivian river dolphin was briefly thought to be a subspecies (as I. geoffrensis boliviensis) of the Amazonian river dolphin, Inia geoffrensis, but differences in body structure and the isolation of the Bolivian river dolphin led to it being classified as its own species in 2012. [3] In a study conducted in 2015, it was also noted that any gene flow between I. geoffrensis (downstream) and I. boliviensis (upstream) would be a one way path flowing from upstream to downstream due to the Teotônio waterfall between them. [4] Despite any gene flow, these populations would also remain morphologically different from each other due to the differences in the environment in which they reside. Differences in seasonal water depth and speed would result in morphologically different species. In terms of research that has been conducted or could be conducted, the population size for these freshwater dolphins is incredibly small, making large sample sizes for scientific studies hard to work with. [5]
Although older publications and some recent publications [6] consider the I. g. boliviensis population as distinct species from Inia geoffrensis , much of the scientific community, including the IUCN, [7] consider them to be a subspecies of Inia geoffrensis. Current classification, [8] therefore, considers them a single species, Inia geoffrensis, in the genus Inia, with two recognized subspecies. As of 2016, the Committee on Taxonomy of the Society for Marine Mammalogy [9] supports the designation of two subspecies. A recent study, with more comprehensive sampling of the Madeira system, including above and below the Teotonio Rapids (which were thought to obstruct gene flow), found that the Inia above the rapids did not possess unique mtDNA. [10] As such the species level distinction once held was not supported by further sampling. Therefore, the Bolivian river dolphin is currently recognized as a subspecies.
In September 2012, Bolivian President Evo Morales enacted a law to protect the dolphin and declared it a national treasure. [11]
French naturalist and palaeontologist Alcide Dessalines d'Orbigny explored South America from 1826 to 1833, including a stay in Bolivia from 1831 to 1833. He returned to France in 1834 and started to describe his scientific explorations, including the new Bolivian cetacean species "Inia boliviensis". In 1847, he and Paul Gervais compared it to "Delphinius geoffrensis" (=Amazon river dolphin, Inia geoffrensis), which had been described from a stuffed specimen in Lisbon, and the two were considered synonyms for more than a century. In 1973, however, a fresh study concluded that the specimens from Bolivia had more teeth than the specimens from elsewhere and that the rapids and water falls of the Madeira River acted as a barrier, effectively isolating the Bolivian population. The Bolivian river dolphin was therefore made a subspecies, Inia geoffrensis boliviensis. Morphological studies later in the 1970s added to the differences between the populations and the specific status Inia boliviensis was restored. There is, however, still no consensus on the taxonomic status of the Bolivian population (or that of the Orinoco River population, "I. g. humboldtiana"). [12]
The Bolivian river dolphin, or Inia boliviensis, is one of four freshwater river dolphin species in South America. Locally known as bufeos, it is found in some rivers in the Upper Madeira Basin of the Bolivian Amazon. [3] The Bolivian river dolphins are separated from the Amazonian River Dolphins by a series of rapids and falls. [13] The pink river dolphin is the largest freshwater dolphin in the world. It can reach up to 2.8 metres (9.2 ft) long and weigh as much as 180 kilograms (400 lb). Compared to its cousin, the Amazonian river dolphin (Inia geoffrensis), the Bolivian river dolphin has more teeth, a smaller skull, and a longer body. [2]
Necropsies have shown the Bolivian river dolphin diet includes a variety of different species of fish, as well as crabs. In the necropsy of a juvenile dolphin, multiple different species of fish from at least 4 different families were found in its stomach contents. It is also worth noting that none of the species present in this particular juvenile's stomach were target species for fisheries. [13]
The dolphins are difficult to observe in the murky river water. However, in April 2022, three ecologists published photographs of Bolivian river dolphins play with a large (presumably dead) Beni Anaconda snake. [14] [15]
The Amazon river dolphin, Inia geoffrensis, is classified as endangered by the IUCN Red List. The Bolivian river dolphin faces a multitude of threats. Overfishing, deforestation, and hydroelectric construction are all major factors in the current population decline. [3] Fisheries also pose a threat to the dolphins, for fishermen might see the dolphins as competition for fish. Deceased dolphins have been noted to have wounds from nets, as well as cuts and mutilation most likely caused by humans. [3] River dolphins are some of the most at-risk marine animals worldwide due to their limited habitats and threats from land.
Since the construction of the two hydroelectric dams in the segment of river where Bolivian river dolphins are found in 2008, the movement of the river has been blocked into two reservoirs of about 300 and 350 km2. Each dam is equipped with mechanisms to promote fish transportation between the reservoirs to prevent the populations from being evolutionarily cut off, however, it is unlikely the Bolivian river dolphins will use these transports. The upstream and downstream populations of I. boliviensis have been cut off by the design of the transport, as they can sustain only short bursts of swimming through high velocity water, and the transports are shallow and narrow with high velocity water, providing an effective barrier between populations. The dams can also cause a change to the fish community structure, and therefore altering the diet of Bolivian river dolphins. [16]
Conservation efforts to prevent further population decline of freshwater dolphins can begin with protecting areas from human influence. Limiting or removing boat traffic, creating better marine animal passageways through dams, and working with fisheries to live alongside wildlife instead of fighting against it are all important steps. Preserving habitats is important for species richness, genetic diversity, and ecosystem complexity. [16]
Bolivian river dolphins are elusive and difficult to observe, as they typically swim below the surface. [17]
In August 2021, a research team observed two sexually aroused juvenile male dolphins near the Tijamuchi River playing with a Beni anaconda (Eunectes beniensis). [18]
Cetacea is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel themselves through the water with powerful up-and-down movement of their tail which ends in a paddle-like fluke, using their flipper-shaped forelimbs to maneuver.
A dolphin is an aquatic mammal in the clade Odontoceti. Dolphins belong to the families Delphinidae, Platanistidae, Iniidae, Pontoporiidae, and possibly extinct Lipotidae. There are 40 extant species named as dolphins.
The Amazon river dolphin, also known as the boto, bufeo or pink river dolphin, is a species of toothed whale endemic to South America and is classified in the family Iniidae. Three subspecies are currently recognized: I. g. geoffrensis, I. g. boliviensis and I. g. humboldtiana. The position of the Araguaian river dolphin within the clade is still unclear. The three subspecies are distributed in the Amazon basin, the upper Madeira River in Bolivia, and the Orinoco basin, respectively.
River dolphins are a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant river dolphins are placed in two superfamilies, Platanistoidea and Inioidea. They comprise the families Platanistidae, the recently extinct Lipotidae, Iniidae and Pontoporiidae. There are five extant species of river dolphins. River dolphins, alongside other cetaceans, belong to the clade Artiodactyla, with even-toed ungulates, and their closest living relatives the hippopotamuses, from which they diverged about 40 million years ago. Specific types of dolphins can be pink.
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 with the Ganges river dolphin and the Indus river dolphin being subspecies. 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 the only living members of the family Platanistidae and the superfamily Platanistoidea. Fossils of ancient relatives date to the late Oligocene.
Iniidae is a family of river dolphins containing one living genus, Inia, and four extinct genera. The extant genus inhabits the river basins of South America, but the family formerly had a wider presence across the Atlantic Ocean.
Platanistidae is a family of river dolphins containing the extant Ganges river dolphin and Indus river dolphin but also extinct relatives from freshwater and marine deposits in the Neogene.
The tucuxi, alternatively known in Peru bufeo gris or bufeo negro, is a species of freshwater dolphin found in the rivers of the Amazon basin. The word tucuxi is derived from the Tupi language word tuchuchi-ana, and has now been adopted as the species' common name. Despite being found in geographic locations similar to those of 'true' river dolphins such as the boto, the tucuxi is not closely related to them genetically. Instead, it is classed in the oceanic dolphin family (Delphinidae).
Inia is a genus of river dolphins from South America, containing one to four species.
The Clymene dolphin, in older texts known as the short-snouted spinner dolphin, is a dolphin endemic to the Atlantic Ocean. It is the only confirmed case of hybrid speciation in marine mammals, descending from the spinner dolphin and the striped dolphin.
Boto is a Portuguese name given to several types of dolphins and river dolphins native to the Amazon and the Orinoco River tributaries. A few botos exist exclusively in fresh water, and these are often considered primitive dolphins.
The baiji is a possibly extinct species of freshwater dolphin native to the Yangtze river system in China. It is thought to be the first dolphin species driven to extinction due to the impact of humans. This dolphin is listed as "critically endangered: possibly extinct" by the IUCN, has not been seen in 20 years, and several surveys of the Yangtze have failed to find it. In China, the species is also called the Chinese river dolphin, Yangtze river dolphin, Yangtze dolphin and whitefin dolphin. Nicknamed the "Goddess of the Yangtze", it was regarded as the goddess of protection by local fishermen and boatmen. It is not to be confused with the Chinese white dolphin or the finless porpoise. This is the only species in the genus Lipotes.
The Tijamuchi River is a river of Bolivia. It is known for its significant river dolphin population.
The Burrunan dolphin is a proposed species of bottlenose dolphin found in parts of Victoria, Australia first described in 2011. Its exact taxonomy is debated: numerous studies support it as being a separate species within the genus Tursiops and occupying a basal position within the genus, with limited phylogenetic studies using different methodologies indicate that it is a subspecies of the Indo-Pacific bottlenose dolphin. The Burrunan dolphin is not currently recognized as a species by the Society for Marine Mammalogy or American Society of Mammalogists, which cites problematic methodology in the original study proposing species status and recommends further research.
The Araguaian river dolphin or Araguaian boto is a South American river dolphin population native to the Araguaia–Tocantins basin of Brazil.
Cetaceans form an infra-order of marine mammals. In 2020, approximately 86 species of cetaceans had been identified worldwide. Among these species, at least 35 have been sighted in the wider Caribbean region with very widespread distribution and density variations between areas. Caribbean waters are a preferred breeding site for several species of mysticeti, who live further north the rest of the year. The tucuxi and the boto live at the southern periphery of the Caribbean region in the freshwaters of the Amazon River and surrounding drainage basins.
Saurocetes is an extinct genus of probable iniid river dolphins from South America. Two species have been described: S. argentinus and S. gigas. It has been suggested that Saurocetes is a synonym of the possible platanistid Ischyrorhynchus.
