Irrawaddy dolphin: where and when to see them

The Irrawaddy dolphin is a blunt-headed cetacean inhabiting scattered coastal, estuarine and freshwater environments in South and Southeast Asia. It is not exclusively a river dolphin, despite its name and several well-known river populations. Small, isolated groups face severe risks from entanglement, altered waterways and habitat degradation. Indonesia and Thailand retain important populations, while Vietnamese occurrence is much less dependable as a basis for visitor observation planning.

Size

2–2.7 m long

Weight

90–200 kg

Lifespan

Not reliably established

Status

Endangered

Irrawaddy dolphins generally form small groups and surface quietly, often showing the rounded head before the back and low dorsal fin. They use echolocation in murky water and may spit streams of water during feeding or social activity. Some populations show distinctive relationships with local fishing practices, but these cannot be assumed everywhere. Mothers keep calves close, and repeated boat approaches can interrupt feeding, movement and opportunities to rest. Irrawaddy dolphins are known for their unique 'spitting' behavior, expelling a stream of water from their mouth, which is thought to be related to feeding or play. They exhibit a 'tail-slap' behavior, often seen when they are feeding or perhaps communicating. Social structures typically involve small, cohesive groups, but individuals may also be seen alone or in pairs.

• Some populations live entirely in freshwater, while others inhabit marine coasts.
• Its neck is more flexible than that of many oceanic dolphins.
• Water-spitting behaviour has been documented in several populations.
• The Australian snubfin dolphin was recognised as a separate species in 2005.

Timing must be population-specific rather than assigned across the species' range. Lower river levels may simplify viewing in some inland settings, while coastal observation depends strongly on sea state. Obtain current local advice because access, population condition and responsible viewing arrangements can change. Water levels in rivers can fluctuate significantly with monsoons, affecting both prey availability and dolphin distribution. Observing dolphins during lower water periods in rivers might increase visibility as they concentrate in deeper channels. Coastal viewing is best in calm seas when dolphins are more likely to be seen at the surface and less impacted by rough conditions.

Habitats include muddy estuaries, sheltered coastal waters, lagoons and a few major rivers. Different populations occupy very different settings, so marine and freshwater records must not be conflated. Indonesia's Mahakam population is inland, whereas other populations use coastal and brackish environments. They are found in scattered, disjunct populations, generally preferring depths less than 20 meters. These dolphins thrive in areas with extensive mangrove forests and estuaries, which offer abundant food sources and shelter. Some populations are known to reside year-round in specific river systems far from the sea.

Fish dominate the diet, supplemented by crustaceans and cephalopods in marine habitats. Available prey differs between river and coastal populations. Echolocation helps locate animals in sediment-rich water, and feeding grounds frequently overlap fishing areas where entanglement presents a serious threat. In addition to active hunting, they are opportunistic feeders and may scavenge discards from fishing boats. Their varied diet reflects their adaptability to different aquatic environments, from freshwater rivers to coastal marine areas. They often forage in turbid waters, relying heavily on their echolocation to detect prey.

Common name

Irrawaddy dolphin

Scientific name

Orcaella brevirostris

Animal group

Mammals

Size

2–2.7 m long

Weight

90–200 kg

Lifespan

Not reliably established

Status

Endangered

Identification

Its rounded forehead, absent obvious beak and small rounded dorsal fin distinguish it from bottlenose and humpback dolphins, while the similar Australian snubfin dolphin has a separate range. Their distinctive blunt, rounded head and lack of a prominent beak are key features for identification, making them appear somewhat whale-like. The coloration is generally dark grey to bluish-grey on the back, fading to a lighter belly, with no complex patterns. Look for their characteristic slow, rolling surfacing pattern, often revealing only the head and a small, triangular dorsal fin.