The Indian Ocean humpback dolphin (Sousa plumbea) is a member of the Delphinidae family occupying coastal areas ranging from Southern Africa to Western Indochina. The Indo-Pacific humpback dolphin (Sousa chinensis) was formerly included within the same species, but a 2014 study revealed them to be a separate species.
The most limiting factor to habitat-usage is water depth, with most specimens remaining in waters shallower than 20 meters. As a result, the Indian Ocean humpback dolphin's offshore range is largely dependent on the coastlines' specific physiographical characteristics. The species has been reported to inhabit nearly every type of coastal habitat, although preference and prominence of any given habitat type is highly dependent on the geographical location. Indian Ocean humpback dolphins experience extremely high rates of calf and juvenile mortality due to anthropogenic disturbances such as environmental pollution, habitat deterioration and noise pollution.
Indian Ocean humpback dolphins are social delphinids that live in groups averaging twelve individuals, although group size can be highly variable. The majority of their diet is composed of sciaenid fishes, cephalopods, and crustaceans.
The species is currently categorized as Endangered.
Distribution and habitat
Distribution
Sousa plumbea ranges from Southern Africa to Western Indochina, including coastal areas along East Africa, the Middle East and India. There is studied population in Menai Bay Conservation Area of Tanzania's Zanzibar Archipelago. Critically important populations have been determined in Southeast Asia, particularly along the southern coastlines of China. Recent investigations have, however, similarly determined critical populations along the coasts of the Arabian peninsula, particularly including the Sultanate of Oman and the United Arab Emirates.
While S. plumbea and S. chinensis are genetically distinguishable, delphinids' high capacity for hybridization have resulted in hybrid populations in areas of overlapping distribution. In fact, genetic analysis has indicated that S. chinensis sampled from Indochina are more closely related to S. plumbea than to S. chinensis from Australia.
This species does not exhibit large migratory behavior.
Description
The Indian Ocean humpback dolphin is a medium-sized dolphin that ranges in length from and in weight from . They have a fatty hump on the back, which differentiates them from S. chinensis which have a more prominent dorsal fin, but no hump. They are generally dark gray. As a result, a number of nations have preemptively established conservation and management programs to ensure that the species' does not become endangered.
Recent investigative studies have revealed that the United Arab Emirates houses one of the world's largest populations.
Gallery
<gallery mode="nolines">
File:Indian Humpback Dolphin, Kerala, IN imported from iNaturalist photo 306681934.jpg|Dorsal fin on an Indian Ocean Humpback Dolphin
File:Indian Humpback Dolphin, India imported from iNaturalist photo 45311838.jpg|Pattern observed on the dorsal fin of Indian Humpback Dolphins
File:Indian Humpback Dolphin, Kerala, IN imported from iNaturalist photo 306681293.jpg|Profile of the Indian Ocean Humpback Dolphin as visible on the surface
File:Indian Humpback Dolphin, Dhofar, OM imported from iNaturalist photo 473647665.jpg|Blowhole of an Indian Ocean Humpback Dolphin visible on the surface
File:Indian Humpback Dolphin, Dhofar, OM imported from iNaturalist photo 473647604.jpg|Beak of an Indian Ocean Humpback Dolphin visible above the surface
File:Indian Humpback Dolphin, Abu Dhabi, AE imported from iNaturalist photo 471591756.jpg|A Pod of Indian Ocean Humpback Dolphins
File:Indian Humpback Dolphin, Maharashtra, IN imported from iNaturalist photo 60110813.jpg|Indian Ocean Humpback Dolphin lunging out of water
File:Indian Humpback Dolphin, Kerala, IN imported from iNaturalist photo 352515146.jpg|Indian Ocean Humpback Dolphin surfacing
File:Indian Humpback Dolphin, Kerala, IN imported from iNaturalist photo 455250041.jpg|Tail-walking exhibited by Indian Ocean Humpback dolphin
File:Indian Humpback Dolphin, Kerala, IN imported from iNaturalist photo 368125482.jpg|Carcass of Indian Humpback Dolphin washed ashore Kerala coast
</gallery>
See also
- List of cetaceans