Chinese white dolphin
The Indo-Pacific humpback dolphin (Sousa chinensis) is a species of humpback dolphin. This species is often referred to as the Chinese white dolphin in mainland China, Macao, Hong Kong, Taiwan, and Singapore as a common name. Some biologists regard the Indo-Pacific dolphin as a subspecies of the Indian Ocean humpback dolphin which ranges from East Africa to India. However, DNA testing studies have shown that the two are distinct species.
An adult Indo-Pacific humpback dolphin is grey, white, or pink and may appear as an albino dolphin to some. Populations along the coasts of China and Thailand have been observed with pink skin. The pink color originates not from a pigment, but from blood vessels that were overdeveloped for thermoregulation. Calves are dark grey or black at birth. Their coloration lightens through a mottled grey as they age.
These dolphins are found in coastal waters of the eastern Indian and Western Pacific Oceans. They mainly live in the waters of Lantau North, Southeast Lantau, the Soko Islands, and Peng Chau. A code of conduct regulates dolphin-watching activity in Hong Kong waters. Nánpēng Islands Marine Sanctuary in Nan'ao County is also home to local pods. Hepu National Sanctuary of Dugongs and waters around Sanya Bay and other coasts adjacent to Hainan Island are also home to some dolphins. They are also present in waters near the nature sanctuary of Weizhou and Xieyang Islands. Gulf of Tonkin waters in Vietnam may have unstudied populations that may appear elsewhere such as along Xuân Thủy National Park and Hòn Dáu Island in Hải Phòng. Indo-Pacific humpback dolphins prefer to stay in bays, coastal lagoons, estuaries, over rocky reefs, mangrove swamps and rarely occur more than a few kilometers from shore.
Indo-Pacific humpback dolphins are social and live in small groups, generally with fewer than 10 individuals. They also hunt together in a group using echolocation. Adult dolphins come to the water surface to breathe for 20 to 30 seconds before diving deep again, for 2-8 minutes. Dolphin calves, with smaller lung capacities, surface twice as often as adults, staying underwater for 1-2 minutes. Adult dolphins rarely stay underwater for more than 4 minutes. They sometimes leap completely out of the water. They may also rise up vertically from the water, exposing the dorsal half of their bodies. A pair of protruding eyes allows them to see clearly in both air and water.
Indo-Pacific humpback dolphins are carnivores (piscivores, molluscivores). They mainly feed on a wide variety of fish, and mollusks. They also supplement their diet with crustaceans.
Indo-Pacific humpback dolphins breed from the end of summer to autumn. Calves are born after a gestation period that usually lasts 11 months and they measure 1 m (3 ft 3 in). The mother stays with her single calf until it can find food for itself, usually when it reaches 3-4 years of age. Females of this species become reproductively mature and start to breed at around 10 years of age, while males mature when they are around 13 years old.
Indo-Pacific humpback dolphins are threatened by habitat loss, water pollution, coastal development, overfishing, and an increase in marine traffic within its range. They are at particular risk of exposure to organic pollutants because they inhabit shallow coastal waters, which are often impacted by human activities. Anthropogenic pollutants pose a risk to marine mammals that reside in coastal waters. Plastic pollution can also interfere with dolphins' use of echolocation. Echolocation is the main sense that all dolphins use to navigate, as well as to pinpoint prey and predators. Dolphins and whales use echolocation by bouncing high-pitched clicking sounds off underwater objects, similar to shouting and listening for echoes. The sounds are made by squeezing air through nasal passages near the blowhole. These sound-waves then pass into the forehead, where a big blob of fat called the melon focuses them into a beam. This process can be interrupted by noise pollution, as well as by obstructions in the water such as masses of oil or plastics. Large blockages in the water can refract sound-waves, misleading the dolphin to falsely detect prey, kin, or a predator in the area. This can become confusing and frustrating which can lead to extreme stress and potential health issues.
The IUCN Red List and other sources don’t provide the number of the Indo-Pacific humpback dolphin total population size. Currently, this species is classified as Vulnerable (VU) on the IUCN Red List, and its numbers today are decreasing.