Chinese White Dolphin
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The Chinese White Dolphin (}; }) (Sousa chinensis chinensis) , also called Indo-Pacific Humpback Dolphin is a subspecies of the Humpback dolphin and is one of eighty cetacean species. The adult dolphin has a unique pink-coloured skin. The colour of the skin is not a result of colour pigmentation, but is actually from blood vessels used for thermoregulation to prevent overheating during exertion. The adult's body length is about 220 - 250 centimetres and the infant's body length is about 1 metre. The average weight of an adult is around 150 to 230 kilograms.
The Indo-Pacific dolphins can be found throughout Southeast Asia, and they breed from South Africa to Australia. There are two subspecies, with Sumatra, one of the Indonesian islands, as the dividing line between the Chinese and the Western subspecies, Sousa chinensis plumbea.
The two subspecies differ in color and size of their dorsal fin.
The subspecies found in Southeast Asia has pinkish white skin and a larger dorsal fin but lacks the fatty hump of its South African and Australian counterparts.'''
Color changes in growth period
- Birth: Black in color.
- Childhood: Grey in color.
- Youth age: Pinkish grey with spots.
- Adult: Pinkish white and the spots will fade out.
Life expectancy
A Chinese White Dolphin can live as long as 40 years. The eldest dolphin lives in Hong Kong and is known to be about 33 years old. Scientists have discovered that the age of a dead dolphin can be determined by observing the cross section of its teeth.
Behaviour
Chinese White Dolphins swim to the water surface to breathe every twenty to thirty seconds and after that they will dive into deep water again. A calf surfaces from the water twice as much as an adult. This is because calves have a smaller lung capacity than an adult. Adult dolphins can stay underwater for about two to eight minutes but a calf can only stay underwater for one to three minutes. On average, adult dolphins rarely stay under water for more than four minutes.
They sometimes jump out of water and expose their whole body. This behavior, called breaching, is often impressive to human observers. Besides jumping out of water, White Dolphins also come up vertically out of the water, exposing the front half of the body. They have a pair of protruding eyes and they can see clearly in both air and water.
Reproductive cycle
Chinese White Dolphins are quite sociable creatures and usually live in small groups of three to four. Female white dolphins become mature at ten years old while the males become mature at thirteen years old. The Chinese White Dolphins usually mate from the end of summer to autumn. Infant dolphins are usually born eleven months after the mating. Mature female white dolphins can give birth every three years and the parental care will last until their offspring can find food themselves.
Population
There are about a thousand Chinese White Dolphins found in the Pearl River Delta, the body of water between Hong Kong and Macau. In Hong Kong waters, the total population of the dolphins is about 450-740, depending on the time of year. For example, in winter, there are about 130 dolphins in Hong Kong waters. The total population of the Chinese White Dolphins found in the whole area of the Pearl River Delta was about 1,050 in 1998.
Dolphin watching
Hong Kong Dolphinwatch Ltd. has been running boat trips to visit the Chinese White Dolphins for the past five years. The dolphins mainly live in the waters of Lantau North, Southeast Lantau, the Soko Islands and Peng Chau. They primarily do this to raise awareness of Hong Kong citizens on the dolphins. Ten percent of the profits of the organization goes into research for Friends of the Earth (HK)'s Water Action Group, which is a charity aimed to raise public awareness of Hong Kong's coastal environment (see ecology of Hong Kong).
Threats
The sea of Hong Kong is becoming a very dangerous habitat for the Chinese White Dolphins. This is due to the increasing numbers of poaching, landfills, and sea traffic. Since Chinese White Dolphins are territorial animals and rarely stray far away from their habitat, the water pollution in Hong Kong has a high impact on them.
Industrial, agricultural, and domestic sewage are amongst the threats to the dolphins. In the Pearl River Delta, about 190,000 cubic metres of sewage is drained into the sea without any treatment daily. The raw sewage and industrial pollutants affect the dolphins as well as the whole ecosystem. The large amounts of heavy metals, such as mercury, and organic materials that have been found by scientists in the corpses of Chinese White Dolphins indicates that tributyltin (TBT), an anti-fouling agent, and organochlorines, such as PCBs and DDT, have entered the dolphins' food chain. These have had a negative impact on the immune systems of the dolphins.
As mentioned above, the construction of the Chek Lap Kok Airport resulted in a 9.5 square kilometer loss of prime dolphin habitat. Other construction projects like the North Lantau Expressway, river trade terminal between Tuen Mun and Castle Peak Power Station, and the Disney's Theme Park, need further reclamation. This will lead to a yet more severe loss of dolphin habitat.
Overfishing and heavy boat traffic near northern Lantau also threatens the lives of the dolphins. Overfishing may be a major danger to the dolphins because there are few regulations on the fishing industry set by the Hong Kong Government. There are many fish that are caught which become bycatch ('trash fish') because they are not the right size or species to be sold for profit. Therefore, dolphins risk both being caught and becoming bycatch. As for boat traffic, about 70 boats pass an average Hong Kong shipping channel daily (Mak, 1996). Boat engine noise interferes with the dolphins' communication channels through animal echolocation.
Origin of a Cantonese slang
The Cantonese has a slang "Wu Gei Bak Gei" (often written as 烏忌白忌, lit. "black taboo white taboo") which means someone being a bad omen or a nuisance etc. The phrase originates from the Cantonese fishermen, because they claim that the dolphins eat the fish in their nets.However, in proper Chinese, it should be written as 烏鱀白鱀, with the "Gei" originally in olden Chinese, means dolphins. The "Wu" referring to the finless porpoises, which are black, and the "bak",white, referring to Chinese River Dolphins. These two species often interrupt and ruin the fishermen's catch. As years passed, because "dolphin" sounds the same as "bad luck", the meaning of the phrase changed. However, in Cantonese, the "wu" refers to the calves of Chinese White Dolphin and "bak" refers to the adults. Note that River Dolphins (Baiji) do not exist in Hong Kong. Nowadays, dolphins are not called "gei" anymore, but 海豚 (Hoi tuen), meaning "Sea pig".
Timeline of main events
- 1637: The Chinese White Dolphin was first discovered in Hong Kong by an adventurer Peter Mundy near the Pearl River. The species are attracted to the Pearl River Estuary because of its brackish waters.
- Late 1980s: Environmentalists started to pay attention to the Chinese White Dolphin population.
- Early 1990: The Hong Kong public started to become aware of the Chinese White Dolphin. This was due to the side effects of the construction of the Chek Lap Kok Airport. It was one of the world's largest single reclamation projects: the reclamation of nine square kilometers of the seabed near Northern Lantau, which was one of the major habitats of the dolphins.
- Early 1993: Re-evaluation of the environmental effects of the construction of Chek Lap Kok Airport. This alerted eco-activists such as those from the World Wide Fund for Nature in Hong Kong, in turn bringing media attention on the matter. Soon enough, the Hong Kong Government began getting involved by funding projects to research on the Chinese White Dolphins
- Late 1993: The Agriculture, Fisheries and Conservation Department was funded.
- 1996: Dr. Thomas Jefferson began to conduct research on the Chinese White Dolphin's in hope of discovering more about them.
- 1997: The Chinese White Dolphin became the official mascot of the 1997 sovereignty changing ceremonies in Hong Kong.
- 1998: The research results of Dr. Thomas Jefferson was published in "Wildlife Monographs".
- 1998: The Hong Kong Dolphinwatch was organized and began to run dolphin watching tours for the general public to raise the public's awareness of the species.
- 2000: The Agriculture, Fisheries and Conservation Department started to conduct long-term observation of the Chinese White Dolphins in Hong Kong.
- 2000: The population of Chinese White Dolphins has reached around only 80-140 dolphins in the Pearl River waters.
External links
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