Presentation on theme: "Sousa chinensis Indo-pacific humpback dolphin Note: I do not claim ownership of any pictures used in this PowerPoint."— Presentation transcript:
Sousa chinensis Indo-pacific humpback dolphin Note: I do not claim ownership of any pictures used in this PowerPoint.
Physical appearance Despite their name, Chinese white dolphins are born black, instead of pink or white. However, the colours change to grey during childhood, pinkish grey with spots during ‘youth age’ (maybe the dolphin equivalent of adolescence) and stay at a bright pink without spots after maturity. Since the dolphins are bright pink, you might wonder why they are called Chinese white dolphins. There are two theories that explain why they are pink, and the first one says that the colour comes from pigments in the skin. The second theory says that the pinkish colour they have is ”not a result of colour pigmentation, but is actually from blood vessels used for thermoregulation to prevent overheating during exertion” (http://en.wikipedia.org/wiki/Chinese_white_dolphin), which means that they are pink because they ‘flush’ to spread heat. Also, researchers have found that dead dolphins are milky white, providing evidence for the second theory. Newborn dolphins are usually 1m long, but can grow to a staggering 2.8m at adulthood. As adults, males can be up to 2.8m long and weigh 260kg, while females are usually 2.4m long and weigh 170kg.
Distribution Firstly, according to the Hong Kong Dolphin Conservation Society, there are at least 1400 dolphins frequenting the Pearl River Estuary, with 300 of them in Hong Kong waters. As you can see from the chart marked in red, the dolphins seem to like frequenting estuaries, such as the one in the west of Hong Kong. This basically includes the waters north, south and west of Lantau Island, as well as a place called Deep Bay. However, if you want to know where they can be found around the world, please refer to the chart marked with green. As you can see, they can be found in southern China, Hong Kong, Thailand, the Philippines, and northern to eastern Australia.
Threats One of the really obvious threats is pollution. Basically, according to all my sources, stuff called ‘organochlorines’(hydrocarbon pesticides, such as DDT, that contain chlorine - have been found in dolphins, and the concentrations of the organochlorines is significantly higher than in seals from around the world. Also, the dolphins inhabit an area in Hong Kong where there is a lot of sewage waste discharge and contaminated mud pits, which basically means that the chances of there being metals in the dolphins is greater. Although the concentrations of arsenic, chromium, lead, molybdenum and nickel are lower in dolphins than in their prey, the concentration of mercury is of a magnitude far greater than that in prey, and could be health threatening. As I mentioned before, the area that the dolphins inhabit contains a lot of discharged sewage, which means that the dolphins intake a large amount of sewage bacteria just by ingesting the polluted seawater. To put it simply, it means that the dolphins could ingest up to 70,500 faecal ‘coliforms’ a day. ( A coliform is a rod-like type of bacteria that exists in faeces. A pretty famous example is E.coli, which used to be found in contaminated beef.) Just to put this into context, ingesting coliforms at once is supposed to be unacceptable for humans. Imagine how bad it is for the dolphins!
Threats (2) Other threats include this really obvious one, reclamation. As you may know, since the building of Chek Lap Kok Airport began, a huge load of sea was ‘reclaimed’. In fact, the reclamation resulted in a “9.5 square kilometer loss of prime dolphin habitat” (http://en.wikipedia.org/wiki/Chinese_White_Dolphin), leaving less habitable areas for dolphins. Another threat is the dolphins being by-catch. In case you don’t know what it means, by- catch is all the unwanted stuff that fishermen get while trawling (i.e. if there’s a person fishing for shrimps and catches a whole load of crabs, fishes, and a dolphin, everything except for the shrimps count as by-catch). While the by-catch does get returned to the sea, it’s usually too late, and the by-catch will probably be nearly dead by then. Also, the ecosystem will be disturbed where they dump the by-catch. Besides all that, dolphins can suffer from boat collision injuries, propeller cuts, dolphin watching disturbance and noise pollution. The first 2 are quite obvious, so I won’t elaborate on those. Dolphin watching can potentially harm the dolphins, as that activity isn’t regulated. This basically means that boat captains/skippers are free to go and chase the dolphins once they appear – and, according to the Hong Kong Dolphin Conservation Society, they do. The dolphins get harassed, and may, in the long term, abandon the area where they had been harassed. Again, loss of dolphin habitat. Finally, noise pollution. This basically means that noise generated in the sea near where the dolphins are can disturb them. How? The noise messes up their echolocation, rendering them partially disabled.
Hong Kong Dolphin Conservation Society Simply put, the Hong Kong Dolphin Conservation Society claims to be the main society (besides the Agriculture, Fisheries and Conservation Department) dedicated to the conservation of cetaceans (family of animals including dolphins, porpoises and whales) in Hong Kong. According to its website, which also provides a lot of information on Indo-Pacific humpback dolphins, they hold talks in schools and do research to try to make sure that the dolphins don’t go extinct. However, it also says on their website that ‘ In the past eight years, their (the dolphin’s) number has remained stable with no downward trends thus it is misleading to say that the Chinese white dolphins are an endangered species! ’ (Author unknown, Chinese white dolphin, Chinese white dolphin is close to extinction?, 07/11/2008), followed by a ‘ But that doesn't mean that we don't need to protect the Chinese white dolphins. Prevention is always better than cure. We should work on conserving the dolphins before it is too late. Only if we join hands now to maintain and improve their living conditions will these elegant creatures continue to thrive in Hong Kong and its neighbouring waters for a vibrant marine environment.’ (Author unknown, Chinese white dolphin, Chinese white dolphin is close to extinction?, 7/11/2008)
Bibliography (Picture in title slide) Author unknown, (Picture in slide 1) Author unknown, (Green chart in slide 2) Birgit Gerkman (Bonn, Germany, Sousa chinensis (Osbeck, 1765), (Red chart in slide 2) Author unknown, (Logo edited by me in slide 6) Author unknown,