February 17, 2025
SINGAPORE – Many people living in South-east Asia often think they have to venture to Australia, the US or Japan to participate in whale watching tours, but such marine mammals can also be found in the waters in the region.
Singapore, too, is home to a few of them, including the elusive dugong and the Indo-Pacific humpback dolphin. In 2015, a dead sperm whale was even found in the waters off Tuas.
Mr Marcus Chua, who studies mammals at the NUS Lee Kong Chian Natural History Museum, said the presence of marine mammals shows that local habitats are able to support a population of large predators, or, in the case of the dugong, large herbivores.
Dr Louisa Ponnampalam, the co-founder of Malaysian marine mammal research and conservation group MareCet, added: “The significance of losing (marine mammals) would mean that their habitats can no longer support them.”
“We should be really concerned about our own future should we ever lose them, because it means the sea around us is no longer healthy, and we humans rely so much on the sea for so many things, whether we realise it or not,” said Dr Ponnampalam, who is also a Pew Marine Fellow.
To mark International Marine Mammal Protection Day on Feb 19, The Straits Times spoke with experts about South-east Asia’s marine mammals, the threats they face, and future research opportunities.
Where can they be found?
Marine mammals have been sighted across South-east Asia, one of the world’s marine biodiversity hot spots with more than 3,000 species of fish and 600 types of corals.
In September 2024, for example, a humpback whale was sighted in the waters off Pulau Redang in Malaysia. This was the species’ first sighting off the east coast of Peninsular Malaysia, according to MareCet.
A humpback whale was also sighted in January 2025 off the coast of the Philippines.
Various factors can influence the habitat suitability for the different species of marine mammals, said Dr Ponnampalam. They include:
- Depth
- Temperature
- Distance from shore
- Proximity to estuaries, which are coastal areas where a freshwater river or stream meets saltwater from the ocean
- The presence or absence of certain ecosystems, such as mangroves or seagrass
- Water clarity
- Level of man-made disturbances, such as coastal development, which could contribute to habitat fragmentation and noise pollution
What are some marine mammals found in South-east Asia?
Found off the coasts of the Philippines and Thailand between October and January in search of warmer waters for mating and reproduction, these marine giants can grow to 18.3m in length and weigh up to 36,280kg, or the approximate mass of three to five buses.
Akin to fingerprints on a human, individual whales can be distinguished by the size and shape of their tail flukes, which also have unique patterns of scars and pigmentation. Male humpback whales also produce whale songs as mating calls and to communicate. These complex vocalisations include moans, howls and whistles in “verses” that can last up to 30 minutes and be repeated up to 22 hours consecutively.
Once hunted to the brink of extinction, humpback whale numbers have gradually recovered, thanks to conservation efforts.
Categorised as being vulnerable to extinction, sperm whales can grow up to 18m, with the largest brain of any animal. Its brain develops to five times the volume of human brains, weighing up to 9kg – six times heavier than a human’s.
Their block-shaped heads measure up to a third of their length, and they get their name from a waxy, oil-like substance in its head that was originally mistaken for sperm by early whalers. Called spermaceti, it is believed to assist in echolocation and the whale’s buoyancy.
Though generally spotted off Malaysia, Indonesia, Brunei and Cambodia between April and July for feeding, mating and moulting, the carcass of a sperm whale was beached along Jurong Island in Singapore in 2015.
Nicknamed “Jubi Lee”, it was found with its spine broken in several places, likely from a ship strike. Its skeleton now hangs in the NUS Lee Kong Chian Natural History Museum.
Two more dead sperm whales washed up in Bali, Indonesia in 2023.
An increase in sightings of Bryde’s whales in the region were reported lately, with three spotted in Thai waters in November 2024. This brings the total number of the whales logged by the Thai Department of Marine and Coastal Resources to nine, the department announced in December 2023.
Also found off Indonesia and Brunei, they are among the few whale species to prefer warmer waters above 15 deg C, earning themselves the nickname “tropical whale”.
Like humpback whales, they are active lunge feeders, and can be observed bursting through a dense school of fish with their mouths agape. They often use bubble net foraging, releasing bubbles from depth to herd schools of fish or krill into a ball for easier feeding.
In 1994, the carcass of a false killer whale surfaced on the coast along Tuas, and was mistaken for a shark by two men who discovered it while crab hunting. Its species was later correctly identified by Underwater World Singapore.
Despite their name, they are actually more closely related to Risso’s dolphins and pilot whales than killer whales, and are part of the oceanic dolphin family.
To escape cold waters in the north, they are commonly found off Thailand between December and February. They are generally larger than killer whales and look discernibly different. False killer whales are mostly uniformly dark grey or black with a lighter underside, while killer whales feature a black and white colouration, with a white patch above their eyes and a white underside.
This “near threatened” species of dolphins forage as a school for squid and large fish like tuna and even dolphins, and share their catch with one another.
With a bulging forehead, a round face and a flexible neck, the Irrawaddy dolphin has a distinctive appearance. They are slow swimmers and generally stay well under water and only surface to breathe.
Irrawaddy dolphins grow and weigh up to 2.7m and 130kg respectively.
They can be found in estuaries and the coastal waters of Vietnam, Indonesia, Brunei, Cambodia, Laos and Myanmar, feeding on bony fish and fish eggs. These endangered dolphins herd fish into their hunting area by squirting streams of water that reach up to 1.5m.
There are said to be fewer than 85 individuals left in the Mekong River between Cambodia and Laos, placing the species on the verge of extinction locally.
The Indo-Pacific humpback dolphins have been sighted in estuaries and off the coasts of Singapore, Malaysia, Cambodia, Laos, Myanmar and Vietnam.
Changing their appearance as they mature based on their habitats, only those within the Asian region reportedly develop a pinkish hue. Those outside this range tend to resemble their cousins, the Indian Ocean humpback dolphins and remain uniformly grey.
This region-specific colouration phenomenon remains unexplained. These vulnerable creatures grow up to about 2.8m in length and 280kg in weight.
The only porpoise to lack a dorsal fin, the Indo-Pacific finless porpoise can be spotted in estuaries and shallow coastal waters around Singapore, Malaysia and Thailand.
They seem to prefer waters less than 200m deep with soft or sandy bottoms and spend up to 60 per cent of their time at or near the water surface. This explains their diet comprising primarily small fish, crustaceans, squid, octopus and cuttlefish that live near the surface of waters.
There are three subspecies of the animal dispersed across the waters of Asia and the Indo-Pacific region, and they all produce both high frequency clicking sounds likely for echolocation, and longer, low frequency tones for communication.
Despite resembling whales, dolphins and porpoises, dugongs are believed to be more closely related to elephants. These herbivores are typically sighted in estuaries and shallow coastal waters around Singapore, Malaysia, Indonesia, Cambodia, Vietnam and the Philippines.
Dugongs are commonly known as “sea cows”, due to the significant contribution of seagrass to their diet, with adult dugongs consuming up to 30kg of it daily, said Mr Sirius Ng, a PhD student studying marine mammals at NUS.
As they are found in only areas rich in seagrass, it indicates that the area of water is still able to support the existence of the meadows, which in turn supports the species’ ability to continue existing in an area, said Dr Ponnampalam.
According to Mr Ng, studies have shown that the germination of seagrass seeds speeds up once it has passed through the dugong’s digestive system, and they are later deposited onto the seabed when it defecates.
With a very limited lung capacity, these gentle giants typically spend no longer than three minutes under water. This makes them vulnerable to collisions with vessels and the accidental consumption of floating marine debris when they surface to breathe.
Threats facing marine mammals
Marine litter, including plastic packaging and ropes, as well as discarded or lost fishing gear like nets, lines and traps, can cause significant harm to sea animals.
Ingesting marine debris may lead to gastrointestinal tract damage, while animals that get entangled in plastic pollution may get injured and starve to death – or be left at the mercy of predators. Animals like dolphins, whales and porpoises that need to regularly surface for air may drown due to entanglement.
Dolphins, whales, sharks, turtles and other species have also inadvertently gotten caught during commercial fishing operations such as trawling and drift netting. Entrapment in nets and lines, and accidental capture, can result in injury and death of the bycatch.
According to the Food and Agriculture Organisation of the United Nations, it is estimated that more than 500,000 marine mammals are incidentally captured each year on a global scale.
Ship strikes pose a major threat to marine life as well, with a global average of 30 whales, dolphins and porpoises getting killed each year after being hit by ships.
The risk of ship strikes is high in the waters around Singapore, including the Malacca Strait, which are some of the busiest in the world, said Mr Chua. He added that this risk can be mitigated with the enforcement of vessel speed limits in whale collision hot spots.
Maritime traffic also contributes to underwater noise pollution.
Sound travels much faster and further underwater than in air. With most marine animals relying on sound for communication, and feeding and navigation, loud noises from shipping, military sonar, industrial activities or underwater explosions distress and disorientate them.
Underwater noise pollution can also cause hearing loss in marine mammals and/or alter their acoustic behaviour, but is currently not legally recognised as an official threat to marine life in South-east Asia, said Dr Ponnampalam.
On whale and dolphin watching, she cautioned that watching groups should stay at least 100m from the animals, as getting too close and attempting to swim among them causes stress to the animals and interferes with their natural activities, and that watchers should also report tours to the authorities where the animals are tied up in the water.
Coastal development, including land reclamation and dredging, has also been proving to be an increasing threat to marine life, as it can fragment marine mammals’ habitats, into smaller, isolated areas.
With marine mammals being a key indicator of ocean health, their continued occurrence along Singapore’s hyper-urbanised coastlines highlights the importance of understanding their ecology to better inform future conservation efforts.
Legends from the deep
It was believed that a whale once saved an entire village of people from a monster in Vietnam. Till today, whales are worshipped as deities in temples, and elaborate ceremonial funerals and burials are held for those found stranded or dead at sea.
In Chinese mythology, it is believed that the now-extinct Baiji (Lipotes vexillifer), a freshwater dolphin, was the reincarnation of a young maiden who leapt into the Yangtze River to escape her evil stepfather. The man is also said to have fallen into the water, and was turned into a finless porpoise, or “river pig”, which was reviled and hunted for food.
In China, bones of Indo-Pacific humpback dolphins were sometimes found in temples dedicated to Mazu, the Taoist sea goddess. The bones were traditionally used by sailors and fishermen as an offering for protection at sea.
Unravelling mysteries
“There is so much research that could and should be done, if only we, the community of South-east Asian researchers, had more resources to do so,” said Dr Ponnampalam.
Potential areas of research include bioacoustic research to investigate how underwater noise pollution impacts marine mammals, genetic research to identify movement patterns and the genetic diversity of marine mammal populations in the region, as well as how resilient they are to disturbances.
She added that it is also important to learn about sociocultural interactions and the value of marine mammals in South-east Asia within local communities and conduct ecological research to learn more about marine mammals’ distribution, population abundance, habitat use and behaviour.
This will enable researchers to identify conservation needs for various species.
Dugong tears were historically believed to be a powerful aphrodisiac in Malaysia and Cambodia, and used in the concoction of love potions.