Indo-Pacific bottlenose dolphinTursiops aduncus
Category
- Open Ocean
Description
Indo-Pacific bottlenose dolphins are marine mammals from the family of Delphinidae.
They have a short beak and a curved mouth, giving the impression that they are constantly smiling. They possess a fusiform body (tapered at both ends) with distinct ventral spotting for adults that distinguishes them from Tursiops truncatus. Their dorsal surface is blue-grey or dark grey colour, flippers and extremities are darker while their underside is lighter, often pink-tinted.
Females reach reproductive maturity between 7 and 12 years. Males reach reproductive maturity between 9 and 13 years. Adult males are usually longer and heavier than females. Females have a single external opening while males have distinct anal and genital openings. There are between 20 and 28 teeth on each side of the jaw. Adults range between 175 and 400 cm in body length with a pectoral fin length is around 23 cm and weight approximately 230 kg.
Habitat and ecology
They inhabits tropical and temperate waters. The Indo-Pacific Bottlenose Dolphins have a sporadic presence from Western South Africa, along the edge of the Indian Ocean, including the Red Sea, Persian Gulf, Indo-Malay Archipelago, the Solomon Islands and possibly New Caledonia to the southern half of Japan and south east Australia. They are also found around oceanic islands in region that are isolated from major land masses. Indo-Pacific Bottlenose
Dolphins is found in multispecies assemblages with Humpback Dolphins (Sousa plumbea) and other delphinid species.
They are a flagship, as well as an indicator species, that is, their abundance and health portrays that of the coastal marine ecosystems which they inhabit.
Their diet consists of a range of demersal and reef fishes and cephalopods (example, squid, octopus).
Bottlenose Dolphins communicate via auditory perception. They generate ultrasonic clicks, perceiving the reflected signals from surrounding objects in their vicinity. Every individual also has a signature whistle. Tactile signals are also used, such as rubbing flippers on a fellow dolphin of the same age and sex. This behaviour is also observed during mating and between mothers and their calves.
Indo-Pacific Bottlenose Dolphins are polygamous, that is, males and females mate with more than one partner. Breeding intervals for females lasts between 4 to 6 years. Female reproductive success depends on water depth; shallow water allows for easier detection of predators and lower predation risks by sharks. The gestation period is about 12 months and young ones are born tail first. They can swim immediately as they are born. At birth, calves are between 0.8 and 1.1 m in length and between 9 and 21 kg. Lactation period lasts for about 32 months in the wild.
Conservation and management
According to the IUCN Red List of threatened species, Bottlenose Dolphins are categorised under the ‘Data Deficient’ category. They are widespread in Indo-Pacific coastal waters but there are multiple threats that impact this species. Habitat destruction, pollution, fishing, invasive species, environmental degradation, shipping lanes and illegal hunting are some examples. They are often trapped as bycatch in gillnets and purse seines as well. Tursiops aduncus are listed in Appendix II of CITES, protected under the Marine Living Resources Act and are present in MPAs (Marine Protected Areas) over their entire range.
Did you know?
Dolphins have the ability to switch between not breathing while deep diving and normal breathing while swimming along the surface of the water. They swim up to the surface to breathe through a structure called a ‘blowhole’ at the top of their head. They use echolocation as a means to navigate and hunt.
