About the dolphins

Scientific name / family

Sousa chinensis / delphinidae

Description

The Indo-Pacific Humpback dolphin gets its name from the elongated dorsal fin and humped back appearance which arises from the accumulation of fatty tissue on their backs as they age. They also differ from other dolphin species in relation to their mounded forehead and long beaks.

Male and female Indo-Pacific Humpback Dolphins grow to a length of between 2.6m and 2.7m reaching physical maturity at around 14 years of age (sexual maturity occurs between the ages of 10 to 13 years). In the wild, these dolphins will live to around 40 years of age. Indo-Pacific Humpback dolphins can weigh up to 260kg but more commonly weigh around 200kg.

Skin colours will vary depending on location and age with calves being born grey and lightening with age (particularly the dorsal fin and forehead). Chinese dolphins turn pink as they age.

Distribution

Indo-Pacific Humpback dolphins are distributed from the coast of Africa, the Arabian Sea, Indian waters and beyond to the South China Sea. In Australia they inhabit the tropical waters of the west and east coasts and are classified as rare by the EPA and ‘near threatened, population decreasing’ by the IUCN Red List of Threatened Species.

Habitat

Indo-Pacific Humpback dolphins prefer coastal and estuarine habitats in tropical and sub-tropical regions where waters are less than 20m deep. In our region, this area extends from the The Great Sandy Strait to the Tin Can Inlet. They are not known to be migratory.

Diet

The dolphins live on a diet of fish, prawns, molluscs, crabs, squid and octopus according to the location and season.

Behaviour

Indo-Pacific Humpback dolphins are more leisurely swimmers than some other dolphin species and do not as a rule surf bow waves. They swim in small pods of around five or so dolphins. Each pod is lead by an alpha male, or, on occasion, an alpha female. Males will have raking marks on their bodies from fights with other males over territory, and/or female members of its pod.

Threats

Living close to coasts and rivers, the The Indo-Pacific Humpback dolphin is especially susceptible to pollution as well as shark and fishing nets. Other threats include overfishing of their habitat, noise pollution affecting their sonar location, marine activities, harrassment and coastal development. They have nowhere to go when their environment is damaged.