The Indo-Pacific finless porpoise (Neophocaena phocaenoides) is an aquatic marine mammal found throughout most of the Indian Ocean, as well as the tropical and subtropical Pacific from Indonesia north to the Taiwan Strait. Finless porpoises are the only porpoises to lack a true dorsal fin. Although similar in appearance to dolphins, porpoises are more closely related to narwhals and belugas than to the true dolphins.
The flippers of this porpoise are moderately large, reaching up to 20% of the total body length. Adults are typically a uniform, light grey colour, although some may have lighter patches of skin around the mouth or darker patches in front of the flippers. Newborn calves of the central and eastern subspecies are mostly black with grey around the dorsal ridge area, becoming fully grey after four to six months. However, newborn calves of the western subspecies are a light creamy grey and become darker as they age.
Indo-Pacific finless porpoises live in the coastal waters of Asia, especially around Indonesia, Malaysia, India, and Bangladesh. At the western end, their range includes the length of the western coast of India and continues up into the Persian Gulf. On the eastern edge of their range, they are found throughout the Indonesian archipelago and range north to the Taiwan Strait. Finless porpoises are also one of the species protected at Sundarbans National Park. They inhabit estuaries, shallow bays, mangroves, and rivers. They prefer waters with a sandy or soft bottom.
Indo-Pacific finless porpoises are diurnal. They spend their time singly or as a mother/calf pair or two adults, and in schools of 3 or more individuals. They are not as energetic and showy as dolphins. They do not ride bow waves, and in some areas appear to be shy of boats. Although they don't make acrobatics in the water, finless porpoises are believed to be very active swimmers. They typically swim just beneath the surface of the water and roll to one side when surfacing to breathe. This rolling movement disturbs very little water on the surface, so they are often overlooked when rising to breathe. Surfacing generally lasts for one minute, as they take 3 to 4 quick successive breaths, then quickly submerge into the water. They often surface a great distance from the point where they dive beneath the water's surface. Dives lasting over 4 minutes have been recorded, and a common pattern of behavior is to take one long dive, followed by two shorter ones. Finless porpoises make both high-frequency clicking sounds and longer, low-frequency tones, the latter perhaps being for communication, rather than echolocation. The clicks are narrow-band, with peaks of over 100 kHz.
Indo-Pacific finless porpoises are carnivores (piscivores, molluscivores) and eat fish, crustaceans, and cephalopods. They also consume some plant material, including leaves, rice, and eggs deposited on vegetation.
Finless porpoises are polygynous, which means that one male mates with multiple females. They breed in late spring and early summer. The young are born in spring, summer, or winter, depending on the geographic locality, after a gestation period of 10 to 11 months. Newborn finless porpoises are reported to be 72 to 84 cm (28 to 33 in) in length. It has been claimed that young calves cling to the denticulated area of skin on their mother's back and are carried by her as she swims, but there is no clear evidence of this happening. Calves are weaned when they are 6-15 months old. Young males become reproductively mature at 4 to 6 years of age, and females at 6 to 9 years.
Large numbers of Indo-Pacific finless porpoises are killed by entanglement in gill nets. The other big danger to the species is environmental degradation. They also suffer from hunting, human disturbance, live capture for display, collisions with boats, and noise and chemical pollution.
The IUCN Red List and other sources don’t provide the number of the Indi-Pacific finless porpoise total population size. Currently, this species is classified as Vulnerable (VU) on the IUCN Red List and its numbers today are decreasing.
