Indian Ocean Humpback Dolphin

The 🌊 Indian Ocean humpback dolphin (Sousa plumbea), belonging to the Delphinidae family, inhabits coastal regions extending from Southern Africa to Western Indoundefined. The Indo-Pacific humpback dolphin (Sousa chinensis) was previously considered part of the same species, but a 2014 study has since classified them as distinct.

Water depth poses the primary constraint on habitat usage, with most individuals residing in waters less than 20 meters deep. Consequently, the species' offshore range is heavily influenced by the specific physiographical features of the coastlines. While 🌊 Indian Ocean humpback dolphins can be found in nearly all coastal habitats, their preference and prevalence vary significantly by geographic location. They experience notably high rates of calf and juvenile mortality due to anthropogenic factors, such as environmental pollution, habitat degradation, and noise pollution.

Social in nature, these dolphins typically form groups averaging twelve individuals, although group sizes can vary considerably. Their diet mainly consists of sciaenid fishes, cephalopods, and crustaceans. The species is currently classified as Endangered.

Their range encompasses Southern Africa to Western Indoundefined, including coastal areas along East Africa, the Middle East, and 🇮🇳 India. A studied population exists within the Menai Bay Conservation Area of Tanzania's Zanzibar Archipelago. Critical populations have been identified in Southeast Asia, particularly along 🇨🇳 China's southern coasts. Recent research also highlights significant populations along the Arabian Peninsula, notably in 🇴🇲 Oman and the 🇦🇪 United Arab Emirates.

Although genetically distinguishable, Sousa plumbea and Sousa chinensis exhibit a high propensity for hybridization in overlapping areas of distribution. Genetic analysis suggests that S. chinensis from Indoundefined are more closely related to S. plumbea than to their 🇦🇺 Australian counterparts. Notably, this species does not exhibit large migratory behavior.

Characterized as medium-sized dolphins, 🌊 Indian Ocean humpback dolphins range from 2 to 2.8 meters in length and weigh between 150 to 200 kilograms. They possess a distinctive fatty hump on their back, differentiating them from S. chinensis, which have a more prominent dorsal fin but lack the hump. Across different regions, color variations exist, although young dolphins generally appear gray, with a darker shade on top.

Resembling the Indo-Pacific bottlenose dolphins, but with a hump, they exhibit a unique surfacing motion, emerging at a 30- to 45-degree angle, sometimes showing the full head, before arching their back and occasionally displaying their flukes.

🌊 Indian Ocean humpback dolphins are largely social, typically living in variable group sizes ranging from individual dolphins to groups exceeding 100 individuals. While there is limited scientific evidence of significant inter-species interactions, isolated observations have noted both amicable and aggressive interactions with species like the Indo-Pacific bottlenose dolphin, snubfin dolphin, long-snouted spinner dolphin, and finless porpoise.

The species is particularly vulnerable to the adverse effects of human activities due to its preference for shallow, coastal habitats. Key threats include habitat degradation, by-catch mortality, vessel strikes, and noise pollution. Chemical pollution, particularly organochlorines, poses a significant threat as indicated by tissue analyses of stranded specimens. Several countries have proactively implemented conservation and management initiatives to prevent the species from becoming further endangered. Recent studies have identified the 🇦🇪 United Arab Emirates as housing one of the world’s largest populations of 🌊 Indian Ocean humpback dolphins.