The Finless Porpoise is one of six porpoise species. In the waters around Japan, at the northern end of its range, it is known as the sunameri (砂滑). A freshwater population found in the Yangtze River in China is known locally as the jiangzhu (江猪) or "river pig". There is a degree of taxonomic uncertainty surrounding the species, with the N. p. phocaenoides subspecies perhaps representing a different species from N. p. sunameri and N. p. asiaeorientalis.'
Physical Description Edit
The finless porpoise almost completely lacks a dorsal fin. Instead there is a low ridge covered in thick denticulated skin.
Adults are a uniform, light grey colour. Newborn calves are mostly black with grey around the dorsal ridge area, becoming fully grey after four to six months. Adults grow more than 1.55 m (5 ft) in length and up to 30–45 kg (65–100 lb) in weight. Males become sexually mature at around four to six years of age, and females at around six to 9 years of age.
Finless porpoises are reported to eat fish and shrimp in the Yangtze River, and fish, shrimp and squid in the Yellow Sea/Bohai area and off Pakistan. In Japanese waters, they are known to eat fish, shrimp, squid, cuttle fish and octopuses. They are opportunistic feeders using various kinds of available food items available in their habitat. Seasonal changes in their diets have not been studied. They also apparently ingest some plant material when living in estuaries, mangroves, and rivers, including leaves, rice, and eggs deposited on vegetation.
Like other porpoises, their behaviour tends to be not as energetic and showy as that of dolphins. They do not ride bow waves, and in some areas appear to be shy of boats. In the Yangtze River, finless porpoises are known to leap from the water and perform "tail stands". Breeding occurs in late spring and early summer, after a gestation period of 10–11 months. The calf clings to the denticulated area of skin on their mother's back and is carried by her as she swims. Calves are weaned at 6–15 months.