Species:

Indo-Pacific Humpback Dolphin

Indian Ocean Bottlenose Dolphin

Irrawaddy Dolphin

Finless Porpoise

Dugong

 

 

 

Finless Porpoise (Neophocaena phocaenoides)

Description

Porpoises are generally much smaller than dolphins and the finless porpoise is no exception, growing to around 1.9, in length (40kg). They are dark grey in colour with a slightly paler under-side. The head is small and rounded with no beak. The dorsal fin is absent and has been replaced by a ridge that runs down the middle of the back.

This is the only member of the porpoise family to be found in Singapore waters. Porpoises are distinguished from dolphins by their smaller size, rounded heads and spade shaped teeth.

Distribution:

Finless porpoises are generally found in the coastal waters of the Indo-Pacific, inhabiting both salt and fresh waters. There are three regional populations, which have warranted sub-species ranking based on differences in skull morphology (Rice 1998; Amano 2002). N.p. phocaenoides are found in the coastal waters of mainland Asia from the Persian Gulf to the South China Sea. They are also found in Sumatra, Bangka, Sarawak, Palawan and northern Java. The N.p. sunameri is found along the East China Sea towards Korea and Japan while the N.p. asiaeorientalis is found in the Yangtse River, where it ranges 1,600 km upstream (Rice 1998).

Distribution of the three sub-species of N. phocaenoides,re produced from Culik 2005, Modified from Amano 2002.

 

There is variation in colour between sub-species and locations. N.p.phocaenoides are born pale and become darker with age, almost turning black (Parwsons & Wang, 1989). While young from Japan are black when born and become lighter after a month, when they loose their foetal epidermis (Kasuya, 1999). The dorsal ridge also differs, with the N.p.sunameri and the N.p. asiaeorientalis having narrow, prominent ridges a few centimetres wide while the N.p.phocaenoides ridge is almost flat and wider than 10cm in adults. There are also horny tubercles scattered along the ridge, which are similar to those found on the dorsal fins of other porpoises (Kasuya, 1999).

 

Behaviour:

Like many porpoise species, the finless porpoise is very shy and rarely approach boats. They barely beak the surface when breathing and swim with quick, darting movements.

They are predominantly an inshore species and have been shown to prefer depths of less than 50m off Japan (Amano, 2002). They appear to prefer murky or turbid conditions and areas where river and ocean waters meet (Carwardine, 1995).

Finless porpoises are generally seen as singles or pairs although larger aggregations have been observed on occasion (Jefferson et al., 1993). Unlike dolphins, social structure appears to be limited in this species with the mother/calf pair being the only stable social unit (Kasuya, 1999).

They are known to eat a variety of species, depending on area including fish, shrimp, squid and octopus. They may also ingest plant material including leaves and rice (Jefferson et al., 1993)