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The Amazonian River Dolphin (Inia geoffrensis) is a freshwater river dolphin found in the Orinoco, Amazon
Amazon river dolphin range
and Araguaia/Tocantins River systems of Brazil, Peru, Bolivia, Ecuador, Colombia and Venezuela. It was once listed as 'vulnerable' due to pollution, overfishing, boat traffic and habitat loss but in 2011 it was changed to 'data deficient' due to a lack of current information about threats, ecology, and population number
The Amazon river dolphin is the largest species of river dolphin, with adult males reaching 185 kilograms (408 lb) in weight, and 2.5 metres (8.2 ft) in length. Adults acquire a pink color, more prominent in males, giving it its nickname "pink river dolphin". Sexual dimorphism is very evident, with males measuring 16% longer and weighing 55% more than females. Like other toothed whales, they have a melon, an organ that is used for biosonar. The dorsal fin, although short in height, is regarded as long, and the pectoral fins are also large. The fin size, unfused vertebrae, and its relative size allow for improved manoeuvrability when navigating flooded forests and capturing prey.
They have one of the widest-ranging diets among toothed whales, and feed on up to 53 different species of fish, such as croakers, catfish, tetras and piranhas. They also consume other animals such as river turtles and freshwater crabs.
In 2008, this species was ranked by the International Union for Conservation of Nature (IUCN) as being data deficient, due to the uncertainty regarding its population trends and the impact of threats. While hunting is a major threat, in recent decades greater impacts on population have been due to the loss of habitat and inadvertent entanglement in fishing lines.
It is the only species of river dolphin kept in captivity, mainly in the United States, Venezuela and Europe; however, it is difficult to train and a high mortality is seen among captive individuals.
Description[]
Amazon River Dolphins can grow larger then humans; they are the largest known freshwater cetacean. Females are usually larger then males; the largest female Amazon river dolphins can range up to 2.5 m (8.2 ft) in length and weigh 98.5 kg (217 lb). The largest male dolphins can range up to 2.0 m (6.6 ft) in length and weigh 94 kg (207 lbs)
They can turn their heads 90 degrees due to their un-fused neck vertebrate. Their flexibility is important in navigating through the flooded forests, as rainforest debris can make moving through water difficult. Also, they possess long 'beaks' or 'snouts', which contain 24 to 34 conical and molar-type teeth on each side of the jaws.
Diet[]
The diet of the Amazon river dolphin is the most diverse of the toothed whales. It consists of at least 53 different species of fish, grouped in 19 families, including piranha. The prey size is between 5 and 80 centimetres (2.0 and 31.5 in), with an average of 20 centimetres (7.9 in). The most frequently consumed fish belong to the families Sciaenidae (croakers), Cichlidae, and Characidae (tetras and piranhas). The dolphin’s dentition allows it to access shells of river turtles and freshwater crabs. The diet is more diverse during the wet season, when fish are spread in flooded areas outside riverbeds, thus becoming more difficult to catch. The diet becomes more selective during the dry season when prey density is greater.
Usually, these dolphins are active and feeding throughout the day and night. However, they are predominantly crepuscular. They consume about 5.5% of their body weight per day. They sometimes take advantage of the disturbances made by boats to catch disoriented prey. Sometimes, they associate with the distantly-related tucuxi (Sotalia fluviatilis), and giant otters (Pteronura brasiliensis) to hunt in a coordinated manner, by gathering and attacking fish stocks at the same time. Apparently, there is little competition for food between these species, as each prefers different prey. It has also been observed that captive dolphins share food.
Behavior[]
The Amazon river dolphin are commonly seen singly or in twos, but may also occur in pods that rarely contain more than eight individuals. Pods as large as 37 individuals have been seen in the Amazon, but the average is three. In the Orinoco, the largest observed groups number 30, but the average is just above five. Typically, social bonds occur between mother and child, but may also be seen in heterogeneous groups or bachelor groups. The largest congregations are seen in areas with abundant food, and at the mouths of rivers. There is significant segregation during the rainy season, with males occupying the river channels, while females and their offspring are located in flooded areas. However, in the dry season, there is no such separation. Due to the high level of prey fish, larger group-sizes are seen in large sections that are directly influenced by whitewater (such as main rivers and lakes, especially during low water season) than in smaller sections influenced by blackwater (such as channels and smaller tributaries). In their freshwater habitat, they are apex predators and gatherings depend more on food sources and habitat availability than in oceanic dolphins where protection from larger predators is necessary.
Captive studies have shown that the Amazon river dolphin is less shy than the bottlenose dolphin, but also less sociable. It is very curious and has a remarkable lack of fear of foreign objects. However, dolphins in captivity may not show the same behavior that they do in their natural environment, where they have been reported to hold the oars of the fishermen, rub against the boat, pluck underwater plants, and play with sticks, logs, clay, turtles, snakes, and fish.
They are slow swimmers; they commonly travel at speeds of 1.5 to 3.2 kilometres per hour (0.93 to 1.99 mph) but have been recorded to swim at speeds up to 14 to 22 kilometres per hour (8.7 to 13.7 mph). When they surface, the tips of the snout, melon, and dorsal fins appear simultaneously, the tail rarely showing before diving. They can also shake their fins, and pull their tail fin and head above the water to observe the environment. They occasionally jump out of the water, sometimes as high as a meter (3.14 ft). They are harder to train than most other species of dolphin.
Subspecies[]
Inia geoffrensis geoffrensis inhabits most of the Amazon River, including rivers Tocantins, Araguaia, low Xingu and Tapajos, the Madeira to the rapids of Porto Velho, and rivers Purus, Yurua, Ica, Caqueta, Branco, and the Rio Negro through the channel of Casiquiare to San Fernando de Atabapo in the Orinoco river, including its tributary: the Guaviare.
Inia geoffrensis boliviensis has populations in the upper reaches of the Madeira River, upstream of the rapids of Teotonio, in Bolivia. It is confined to the Mamore River and its main tributary, the Iténez. Inia geoffrensis humboldtiana are located in the Orinoco River basin, including the Apure and Meta rivers. This subspecies is restricted, at least during the dry season, to the waterfalls of Rio Negro rapids in the Orinoco between Samariapo and Puerto Ayacucho, and the Casiquiare canal. This subspecies is not recognized by the Committee on Taxonomy of the Society for Marine Mammalogy, but is recognized by the IUCN.
Communication[]
Like other dolphins, river dolphins use whistling tones to communicate. The issuance of these sounds is related to the time they return to the surface before diving, suggesting a link to food. Acoustic analysis revealed that the vocalisations are different in structure from the typical whistles of other species of dolphins.
Threats[]
The region of the Amazon in Brazil has an extension of 5,000,000 km2(1,900,000 sq mi) containing diverse fundamental ecosystems.[29][30] One of these ecosystems is a floodplain, or a várzea forest, and is home to a large number of fish species which are an essential resource for human consumption.[31] The várzea is also a major source of income through excessive local commercialized fishing.[29][32][33] Várzea consists of muddy river waters containing a vast number and diversity of nutrient-rich species.[22] The abundance of distinct fish species lures the Amazon River dolphin into the várzea areas of high water occurrences during the seasonal flooding.[34]
In addition to attracting predators such as the Amazon river dolphin, these high-water occurrences are an ideal location to draw in the local fisheries. Human fishing activities directly compete with the dolphins for the same fish species, the tambaqui (Colossoma macropomum) and the pirapitinga(Piaractus brachypomus), resulting in deliberate or unintentional catches of the Amazon river dolphin.[35][36][37][29][38][39][40][41] The local fishermen overfish and when the Amazon River dolphins remove the commercial catch from the nets and lines, it causes damages to the equipment and the capture, as well as generating ill will from the local fishermen.[37] [39][40] The negative reactions of the local fishermen are also attributed to the Brazilian Institute of Environment and Renewable Natural Resources prohibition on killing the Amazon river dolphin, yet not compensating the fishermen for the damage done to their equipment and catch.[41]
During the process of catching the commercialized fish, the Amazon river dolphins get caught in the nets and exhaust themselves until they die, or the local fishermen deliberately kill the entangled dolphins.[31] The carcasses are discarded, consumed, or used as bait to attract a scavenger catfish, the piracatinga (Calophysus macropterus).[31][42] The use of the Amazon river dolphin carcass as bait for the piracatinga dates back to 2000.[42]Increasing demand for the piracatinga has created a market for distribution of the Amazon river dolphin carcasses to be used as bait throughout these regions.[41]
Of the 15 dolphin carcasses found in the Japurá River in 2010–2011 surveys, 73% of the dolphins were killed for bait, disposed of, or abandoned in entangled gillnets.[31] The data do not fully represent the actual overall number of deaths of the Amazon river dolphins, whether accidental or intentional, because a variety of factors make it extremely complicated to record and medically examine all the carcasses.[31][36][39] Scavenger species feed upon the carcasses, and the complexity of the river currents make it nearly impossible to locate all of the dead animals.[31] More importantly, the local fishermen do not report these deaths out of fear that a legal course of action will be taken against them,[31] as the Amazon river dolphin and other cetaceans are protected under a Brazilian federal law prohibiting any takes, harassments, and kills of the species.[43]
Conservation[]
In 2008, the International Whaling Commission (IWC) expressed concern for captured botos for use as bait in the Central Amazon, which is an emerging problem that has spread on a large scale. The species is listed in Appendix II of the Convention on International Trade in Endangered Species Fauna and Flora (CITES), and Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals,[44] because it has an unfavorable conservation status or would benefit significantly from international co-operation organized by tailored agreements.
According to a previous assessment by the Scientific Committee of the International Whaling Commission in 2000, the population of botos appears great and there is little or no evidence of population decline in numbers and range. However, increased human intervention on their habitat is expected to, in the future, be the most likely cause of the decline of its range and population. A series of recommendations were issued to ensure proper follow-up to the species, among which is the implementation and publication of studies on the structure of populations, making a record of the distribution of the species, information about potential threats as the magnitude of fishing operations and location of pipelines.[45]
In September 2012, Bolivian President Evo Morales enacted a law to protect the dolphin and declared it a national treasure.[16][46]
In 2018, the species was listed on the Red list of endangered species.[1]
Increasing pollution and gradual destruction of the Amazon rainforest add to the vulnerability of the species. The biggest threats are deforestation and other human activities that contribute to disrupt and alter their environment.[4] Another source of concern is the difficulty in keeping these animals alive in captivity, due to intra-species aggression and low longevity. Captive breeding is not considered a conservation option for this species.[47]
In the Movie[]
Blu and Eduardo are seen in a training session with these dolphins. Eduardo says "under over..." "good job!" and Blu says "thanks". Then Eduardo says "not you" then Blu bumps into a dolphin, getting him wet.
Gallery[]
