Deep in East Kalimantan, the Mahakam River flows through rainforests and floating villages, carrying with it the local myth of two siblings reborn as dolphins. These mythical creatures – Pesut Mahakam – the one freshwater river dolphins in Indonesia, now critically endangered.
Once abundant, their numbers have dropped to around 60, in response to the Rare Aquatic Species of Indonesia (RASI) 2024 report. With roughly five births and five deaths every year, the population stays stagnant and prone to collapse.
What does a Mahakam River dolphin seem like?
Unlike slender oceanic dolphins, the Pesut Mahakam has a rounded head, small eyes, and a smooth, gray body with a pale underside. The short dorsal fin and wide pectoral fins facilitate smooth movement through narrow river bends. Without its long beak, its face appears soft – an adaptation to muddy, shallow freshwater.
This dolphin is modest but powerfully built. Adults normally measure between 1.5 and a pair of.8 meters.
Their weight ranges from 114 to 133 kilograms. Newborns are much smaller, measuring about 96 centimeters and weighing about 12 kilograms.
They grow rapidly in the primary months of life. Over the course of seven months, a calf can gain as much as 59% in length and 266% in weight, a testament to the care and nutrition provided by its mother.
As a carnivore, the Mahakam river dolphin feeds on fish, molluscs and crustaceans, playing a key role in maintaining the ecological balance of the river. They live as much as 30 years and are long-lived inhabitants of those waters, but their slow reproduction makes them delicate.
Breeding takes place from December to June, and males compete in delicate displays. After a gestation period of 9–14 months, females give birth to at least one calf every three years. Sexual maturity takes three to 6 years, making recovery slow and unsure.
Naturally social, Pesut Mahakam dolphins live in small pods of three to 6 individuals. They can often be seen swimming in harmony or interacting with neighboring groups. Like other dolphins, Pesut Mahakam can be an intelligent animal.
Why are dolphin numbers declining within the Mahakam River?
Once thriving within the peaceful bends of the Mahakam River, Pesut Mahakam now lives a quieter and more fragile life. Its survival is threatened by pollution, dwindling food and constant human unrest.
Scientists emphasize that water quality is crucial for the survival of Pesut Mahakam dolphins. Aisyah et al. emphasize that poor pH, low oxygen levels and chemical pollutants disrupt fish populations, making a dangerous ripple effect within the river ecosystem.
1. Deteriorating water quality
Every drop of farm fertilizer, every trace of commercial waste and each stream of domestic sewage eventually results in Mahakam.
Over time, the build-up of nutrients causes eutrophication, which is the excessive growth of algae that depletes oxygen and suffocates aquatic life. What was once a wealthy feeding ground becomes a stagnant, oxygen-deprived river, forcing dolphins to travel further searching for food.
2. Noise pollution
But it is not just the water that changes – it is the sound. Mahakam, once a quiet place, is now bustling with boats, ferries and tourist ships. For echolocation-dependent dolphins, which use high-frequency clicks of 60 to 80 kHz to navigate and find prey, this constant noise is devastating.
Imagine attempting to talk in a room stuffed with roaring engines. This is the on a regular basis lifetime of these dolphins. Research by Kreb and Rahadi, in addition to Beasley et al., shows that boat noise disrupts their communication, often forcing them to place their conversations on hold. Over time, this leads to emphasize, confusion and abandonment of once secure habitats.
3. Hunting for food is dangerous
Food shortage is pushing Pesut Mahakam into danger zones. Many dolphins are drawn to fishing nets, especially rengge nets, to grab trapped fish – for some, this can be a fatal mistake. According to RASI, 70 percent of recorded deaths occur in consequence of dolphins becoming entangled within the water and unable to achieve the surface to breathe.
At the identical time, overfishing and illegal fishing methods corresponding to poisoning and electrocution are worsening the crisis. These destructive practices not only destroy fish stocks, but additionally directly threaten dolphins.
In search of food, some dolphins go upstream – to areas teeming with life, where mining operations and heavy transport traffic happen. The harsh sound of engines, the danger of collisions and murky water polluted by runoff make these regions dangerous territory.
Is it possible to save lots of a dolphin from the Mahakam River?
Although the threats seem overwhelming, hope for Pesut Mahakam has not yet faded. Across East Kalimantan, villages, conservationists and native authorities are quietly constructing a movement to guard the stays of this rare freshwater dolphin.
In the village of Pela near Lake Semayang, change began with grief over repeated dolphin deaths. In 2019, residents took up ecotourism, encouraging visitors to look at dolphins responsibly. Harmful methods corresponding to electric shock, poisoning and the usage of explosives were also completely banned under the brand new village regulations.
Further down the river, innovation meets tradition. With the assistance of RASI, Pertamina Hulu Mahakam and native officials, communities introduced acoustic “pingers” – small devices that send ultrasonic signals – to maintain dolphins away from fishing nets. This easy but effective tool has dramatically reduced the variety of fatal entanglements in high-risk areas.
Meanwhile, education has grow to be a strong ally. Programs corresponding to Kampung Dongeng Etam (Etam Storytelling Village) weave environmental messages into folklore and puppet shows.
Through a project called Domain – short for dongeng dan permainan, which implies storytelling and play – children will learn concerning the ancient legends of Pesut Mahakam not only as stories concerning the past, but additionally as calls to guard their living heritage.
Politics can be catching up. In 2020, the Regency of Kutai Kartanegara issued Decree No. 75/2020 designating a proper protection zone for the Mahakam River and restricting the movement of coal barges through dolphin habitats. While enforcement stays uneven, it signals the start of a brand new awareness that river management must go hand in hand with species protection.
But is all this enough? The survival of the Mahakam river dolphin depends upon local efforts growing right into a broader movement that balances human progress with the rhythm of the river.
Sources:
https://indonesia.go.id/kategori/keanekaragaman-hayati/7210/mengenal-lumba-lumba-di-sungai-mahakam?lang=1
https://fpk.unair.ac.id/mengulik-faktor-terancamnya-sang-hewan-legenda-pesut-mahakam/
https://greennetwork.id/gna-knowledge-hub/bagaimana-desa-wisata-pela-lindungi-keberadaan-pesut-mahakam/
http://ejournal-balitbang.kkp.go.id/index.php/aureliajournal/article/view/11011
https://www.instagram.com/p/DMjlnzJtetr/
