Courtship
Spinner dolphins
Dolphin Species Information
Orca
Length: 5.5-7.5m, max. 9.8m
Weight: 3-6t, max. 7.4-9.8t
Common Names
English: orca, killer whale
Sinhala: makara komaduva, talgas mulla
Tamil: killer thimingilam
Classification
Class: Mammalia Order: Cetacea
Suborder: Odontoceti Family: Delphinidae
Scientific name: Orcinus orca (Linnaeus, 1758)
Sightings
Regular. All year round. Best between December and April (north western to southern seaboard).
Transients have been seen passing along the west coast of Sri Lanka, above or just off the continental shelf, mostly between December and April. Orcas are also sighted off the east coast in September. Other nearby haunts of this cosmopolitan species include the Arabian Sea and the Bay of Bengal, including Ninety East Ridge.
Short-Finned Pilot Whale
Length: 3.7-6m, max. 7.2m
Weight: 1-3t, max. 3.6t
Common Names
English: short-finned pilot whale, pothead whale
Sinhala: komaduva
Classification
Class: Mammalia Order: Cetacea
Suborder: Odontoceti Family: Delphinidae
Scientific name: Globicephala macrorhynchus (Gray, 1846)
Sightings
Occasional, December to June.
Short-finned pilot whales are generally found in deep waters, but move inshore as near as 10km when travelling along the west coast of Sri Lanka. They are known to be nomadic, with no fixed migratory routes, and are widely distributed in the south-eastern Arabian Sea, the Laccadive Sea, the Bay of Bengal and the ocean south of Sri Lanka.
Its scarred body and blunt, squared-off head make an adult Risso’s dolphin unmistakable, though when seen from a distance it may be confused with other large dolphins that sport tall dorsal fins, such as bottlenose dolphins, false killer whales and orcas.
Taxonomic Notes
It is believed that there is evidence of at least two separate subspecies of G. macrorhynchus, but further examination is required to confirm this (Taylor et al., 2014).
Risso's Dolphin
Length: 2.8-3.2m, max. 3.8m
Weight: 300kg, max. 500kg
Common Names
English: Risso's dolphin
Sinhala: Risso’s mulla, malina mulla
Tamil: narai oonjia, panavi meen
Classification
Class: Mammalia Order: Cetacea
Suborder: Odontoceti Family: Delphinidae
Scientific name: Grampus griseus (Cuvier, 1812)
Sightings
All year round. Regular.
Resident (breeding population) but may also be migratory. It is pelagic, usually found in deep oceanic and continental slope waters. Present year-round through most of its range, with some evidence of seasonal movement on the continental shelf in areas such as the Gulf of Mannar. Widely distributed in the Laccadive Sea, off southern Sri Lanka and the Bay of Bengal.
Its scarred body and blunt, squared-off head make an adult Risso’s dolphin unmistakable, though when seen from a distance it may be confused with other large dolphins that sport tall dorsal fins, such as bottlenose dolphins, false killer whales and orcas.
Common Bottlenose Dolphin & Indian Ocean Bottlenose Dolphin
Length: 2-3.1m, max. 3.9m
Weight: 180-300kg, max. 650kg
Length: 2-2.7m, max. 3.2m
Weight: 180-240kg, max. 400kg
Common Names
English: bottlenose dolphin, common bottlenose dolphin
Sinhala: bothal hota mulla, samaanya bothal hota mulla
Tamil: kuppi mukkinai oonjia
Classification
Class: Mammalia Order: Cetacea
Suborder: Odontoceti Family: Delphinidae
Scientific name: Tursiops truncatus (Montagu, 1821)
Common Names
English: Indian Ocean bottlenose dolphin, Indo-Pacific bottlenose dolphin
Sinhala: Indian samudhra bothal hota mulla
Tamil: kuppi mukkinai oonjia
Classification
Class: Mammalia Order: Cetacea
Suborder: Odontoceti Family: Delphinidae
Scientific name: Tursiops aduncus (Ehrenberg, 1833)
Sightings
All year round. Common; abundant off south coast.
Widely distributed all round Sri Lanka in coastal and continental-shelf waters. Population density appears to be higher near to shore. In some areas, common bottlenoses may have limited home ranges; in others, they may be nomadic, accompanying pilot whales as they travel the deep ocean.
There may be two ‘ecotypes’ of the common bottlenose dolphin: a smaller and lighter inshore form and a larger, slightly darker-coloured offshore form.
Seen at close range, common bottlenose dolphins can clearly be distinguished from Indian Ocean bottlenose dolphins by their key characteristics (refer 'Out of the Blue'). They can also be mistaken for humpback dolphins, but will often be distinguishable by differences in body shape, size and behaviour. When seen from a distance, they can also be confused with Risso’s or rough-toothed dolphins.
Sightings
All year round. Occasional.
Though rarely recorded, possibly due to confusion with the common bottlenose and the recent split in taxonomy, Indian Ocean bottlenose dolphins are thought to be fairly common in Sri Lankan waters. They are found primarily over the continental shelf and appear to prefer shallow inshore waters throughout their range.
The slender appearance, sharply contrasting grey dorsal cape with a spinal blaze, lighter belly and relatively longer, thinner rostrum distinguish members of this species from the common bottlenose. Indian Ocean bottlenose dolphins can be mistaken for pan-tropical spotted dolphins and humpback dolphins, but will often be distinguishable by differences in body shape, size and behaviour. From a distance, they may also be confused with Risso’s or rough-toothed dolphins.
Fraser's Dolphin
Length: 2-2.6m, max. 2.7m
Weight: 150-180kg, max. 210kg
Common Names
English: Fraser's dolphin
Sinhala: Fraser's mulla
Tamil: Fraser's oonjia
Classification
Class: Mammalia Order: Cetacea
Suborder: Odontoceti Family: Delphinidae
Scientific name: Lagenodelphis hosei (Fraser, 1956)
The unique body shape and stocky beak of the Fraser’s dolphin should rule out confusion with other species; striped dolphins also have an eye-to-anus stripe but have a longer beak.
Sightings
All year round. Ocassional.
Fraser’s dolphin typically inhabits the high seas and feeds in deep oceanic waters. Members of the species rarely stray into the relatively shallow water over a continental shelf.
Humpback Dolphin
Length: 1.8-2.7m, max. 2.8m
Weight: 60-240kg, max. 280kg
Common Names
English: Indo-Pacific humpbacked/humpback dolphin, Chinese white dolphin (pink dolphin), plumbeous humpback dolphin
Sinhala: kabara mulla
Tamil: koon muthuku oonjia
Classification
Class: Mammalia Order: Cetacea
Suborder: Odontoceti Family: Delphinidae
Scientific name: Sousa plumbea (Cuvier, 1829)
Taxonomic Notes
There are at least two species in the Indo-Pacific area: S. plumbea (Cuvier, 1829) in the western Indian Ocean from South Africa to at least the southeast coast of India, and S. chinensis from the east coast of India to China and Australia. Current understanding is that humpback dolphins in the Gulf of Mannar are members of the western Indian Ocean subspecies, S. plumbea. The two geographic forms differ markedly in their external morphology (iucn 2012). Current studies, both morphological and genetic, were being carried out at time of writing to determine the number of species in this genus.
Humpback dolphins are most likely to be confused with bottlenose dolphins due to similarities in the head region. Differences in dorsal fin shape (including the hump when present), head shape and colour all help distinguish between the two species. Also, humpbacks tend to surface differently, pausing at the top of their roll.
Sightings
All year round. Common.
inshore waters and estuaries at depths of up to 25m. Most commonly found in large aggregations along Adam’s Bridge. In Kalpitiya, a pod of up to five regularly enters Dutch Bay and Puttalam Lagoon to feed. Other unconfirmed reported sightings off Chilaw and Yala.
Striped Dolphin
Length: 1.8-2.5m, max. 2.6m
Weight: 60-150kg, max. 160kg
Common Names
English: striped dolphin
Sinhala: wairam mulla
Tamil: koditta oonjia
Classification
Class: Mammalia Order: Cetacea
Suborder: Odontoceti Family: Delphinidae
Scientific name: Stenella coeruleoalba (Meyen, 1833)
The striped dolphin, with its unique colour pattern, is generally easy to distinguish from Fraser’s dolphin, which also bears an eye-to anus stripe but is much more robust, with tiny appendages.
Sightings
All year round. Occasional.
Oceanic (pelagic). May occasionally be seen close to shore, but only where the water immediately offshore is deep. Widely distributed in the Laccadive Sea and in the waters south and east of Sri Lanka.
Spinner Dolphin
Length: 1.6-1.9m, max. 2.3m
Weight: 50-80kg, max. 100kg
Common Names
English: spinner dolphin, Sri Lankan spinner dolphin, long-snouted spinner dolphin, Gray’s dolphin
Sinhala: karekena mulla
Tamil: sullel oonjia
Classification
Class: Mammalia Order: Cetacea
Suborder: Odontoceti Family: Delphinidae
Scientific name: Stenella longirostris (Gray, 1828)
Taxonomic Notes
Four subspecies of the spinner dolphin, Stenella longirostris, are recognised. These are geographically defined and differ in body shape, size and colour. The subspecies known as the Gray’s or Hawaiian spinner dolphin, S.l. longirostris, with its typical tripartite colour pattern, is thought to be the subspecies present in Sri Lanka. Some spinner dolphins in Sri Lanka and Maldives, however, show a dark lateral stripe between their medium-grey flanks and belly. Representatives of subspecies, or other undescribed stocks, may exist here – and elsewhere in the world as well.
Sightings
All year round. Extremely abundant; extremely so off Kalpitiya peninsula where they are most acrobatic.
Breeding residents, widely and abundantly distributed all round Sri Lanka and in adjacent waters. Superpods and even megapods which were frequently seen off Kalpitiya are now only seen infrequently.
Spinner dolphins can be easily distinguished by differences in size, dorsal-fin shape, beak length. three-toned colour pattern, and particularly by their characteristic behaviour.
Dugong
Length: 2.4-2.7m, max. 3m
Weight: 230-400kg, max. 545kg
Common Names
English: dugong, sea cow. Also known as: lady of the sea
Sinhala: muhudhu oora
Tamil: kadal panni, orgil, avilliya
Classification
Class: Mammalia Order: Sirenia
Suborder: Trichechiformes Family: Dugongidae
Scientific name: Dugong dugon (Müller, 1776)
There is some slight possibility of confusion with the finless porpoise, but in addition to behaviour and size, the single blowhole of the porpoise and the double nostrils of the dugong allow the two species to be easily distinguished.
Sightings
All year round. Very rare.
Warm, shallow coastal waters and estuaries with healthy ecosystems that support large beds of seagrass and/or other vegetation. Habitats in Indo-Sri Lankan waters include Palk Bay and the Gulf of Mannar north of Pukkulum, with strays sometimes entering Dutch Bay. During the monsoon, they typically inhabit the lee side of the Arippu pearl banks, Adam’s Bridge, Palk Bay and the islands west of Jaffna, where they can avoid strong winds and heavy seas. When calm weather returns, they move into the open sea, though still remaining in waters no deeper than 15m.
