Amazon River Dolphin
Tagged: animal, animals, cat, fishInia geoffrensis
The world’s largest river and its tributaries are home to the boto, or Amazon river dolphin. Pollution, dam-building, and overfihing are all threatening the future of this animal. The Amazon river dolphin’s range is naturally broken up into three main stretches of water, separated by extensive or perilous rapids. For this reason some scientists think that there are three distinct subspecies living in the Orinoco River in Venezuela, the Madeira River in Bolivia, and the Brazilian Amazon. However, other biologists maintain that these populations are not as separate as they seem. Every year the rivers flood, allowing large fish¬and maybe also some river dolphins-to swim over and around the rapids. When the waters subside again, the dolphins become trapped, at least until the rains the following year. This phenomenon repeats itself on a smaller scale throughout the dolphin’s range, with animals moving through submerged areas of forest during the flood period and sometimes getting stranded in small lakes for the duration of the dry season.
The Risks of Isolation
The cyclic ebb and flow of flood waters is fairly commonplace in the region, and the dolphins usually manage to survive a season or two in quite small lakes, as long as there are plenty of fish trapped along with them. Problems can arise, however, when the lakes are drained to irrigate crops, or if humans compete for the same fish prey as the dolphins. Once the fish in a lake are gone, no more can arrive to replace them until the forest becomes flooded again the following year. While local activities such as fishing and irrigation threaten isolated groups of dolphins, the building of dams for hydroelectric power and flood control can damage whole populations. Dams create permanent barriers to the dolphins’ passage, cutting off whole populations. These isolated groups can become inbred and vulnerable to disease and local disasters from which there is no escape either up- or downstream. River dolphins are not normally hunted, largely because local legend has it that they harbor the souls of drowned people. The dolphins themselves are frequent victims of accidental drowning after becoming caught up in the huge nets set by local fishermen to take river fish. When this happens, the fishermen are happy enough to make use of the unplanned extra catch by using oil extracted from the dolphins’ bodies as a lubricant and lamp fuel.
Contamination by Mercury
Like other top Amazon predators, including giant otters, river dolphins often suffer from the effects of mercury poisoning. Mercury is used to refine the gold that is mined in the region, and as many as 340 tons (300 tonnes) are released into the river every year. There is also a certain amount of natural mercury present in the soil, and deforestation is increasing the rate at which it is washed into the river by rainfall. Mercury combines with other chemicals to produce a compound called methyl mercury, significant quantities of which then build up in the bodies of river fish. Any animal that eats a lot of contaminated fish ends up ingesting enough methyl mercury to cause serious damage, including birth deformities, muscle-wasting, nerve damage, and failure of the immune system. In humans the condition is known as Minimata disease, after the port in Japan where it was first diagnosed when a factory polluted the local water with mercury. The problem is even more severe for river dolphins, since everything they eat comes from the river.
Amazon river dolphin (boto, pink dolphin
Inia geoffrensis
- Family: Iniidae
- World population: Unknown
- Distribution: Orinoco and Amazon river systems, South America
- Habitat: Rivers and flooded forest
- Size: Length 5.6-10 ft (1.7-3 m). Weight: up to 350 lb (160 kg); males can be almost twice as heavy as females
- Breeding: Single calf born May-September after gestation of 10-11 months; weaned at 1 year or more; maturity depends on size rather than age. Life span 30 years or more
- Related endangered species: Yangtze river dolphin (Lipotes vexillifer); Ganges river dolphin (Platanista gangetica); Indus river dolphin (P.minor)
- Form: Large, bluish-gray to pink dolphin with long dorsal (back) ridge and large fins and tail flukes; small eyes, long snout with peglike teeth, and bulging cheeks and forehead
- Diet: Mostly fish; some crustaceans and turtles
I would like to see more information at the top of this document … I’m not getting very much information. I’m doing a report on these and I can’t find any decant websites!!