A new species of humpback dolphin has been discovered swimming in the waters off the northern coast of Australia.
The humpback dolphin grows up to eight feet in length and ranges from dark gray to pink and/or white in colour.
The species generally inhabits coastal waters, deltas, estuaries, and occurs throughout the Indian and Pacific oceans to the coasts of Australia.
To determine the number of distinct species in the family of humpback dolphins - named for a peculiar hump just below the dorsal fin - researchers from the Wildlife Conservation Society, the American Museum of Natural History, examined the evolutionary history of this family of marine mammals using both physical features and genetic data.
While the Atlantic humpback dolphin is a recognised species, this work provides the best evidence to date to split the Indo-Pacific humpback dolphin into three species, one of which is completely new to science.
"Based on the findings of our combined morphological and genetic analyses, we can suggest that the humpback dolphin genus includes at least four member species," said Dr Martin Mendez, Assistant Director of WCS's Latin America and the Caribbean Programme and lead author of the study.
The authors propose recognition of at least four species in the humpback dolphin family: the Atlantic humpback dolphin (Sousa teuszii), which occurs in the eastern Atlantic off West Africa; the Indo-Pacific humpback dolphin (Sousa plumbea), which ranges from the central to the western Indian Ocean.
Another species of Indo-Pacific humpback dolphin (Sousa chinensis) inhabits the eastern Indian and western Pacific Oceans; and a fourth Sousa species is found off northern Australia yet to be named.
Working to bring taxonomic clarity to a widespread yet poorly known group of dolphins, the authors assembled a large collection of physical data gathered mostly from beached dolphins and museum specimens.
Specifically, the team examined features from 180 skulls covering most of the distribution area of the group in order to compare morphological characters across this region.
The researchers also collected 235 tissue samples from animals in the same areas, stretching from the eastern Atlantic to the western Pacific Oceans, analysing both mitochondrial and nuclear DNA for significant variations between populations.
The Atlantic humpback dolphin is considered "Vulnerable" according to the International Union for Conservation of Nature (IUCN) Red List, whereas the Indo-Pacific dolphin species Sousa chinensis is listed as "Near Threatened."
Humpback dolphins are threatened by habitat loss and fishing activity.
