Indonesian Longfinned Eel Anguilla borneensis

Indonesian Longfinned Eel Anguilla borneensis

IUCN Red List Status: Vulnerable

Locations: Found in Indonesia (Borneo, Sulawesi), Malaysia (Sabah, Sarawak), and the Philippines (Mindanao). Primarily inhabits freshwater rivers, lakes, and streams, with migrations through the Celebes Sea, Sulu Sea, Maluku Sea, and Makassar Strait for breeding.

The Indonesian Longfinned Eel Anguilla borneensis is the only plain-coloured, longfinned #eel found in Indonesia. Gliding like a shadow through the rivers of #Borneo and #Sulawesi, Indonesian Longfinned Eels (Anguilla borneensis) are elusive predators that thrive in the depths of tropical waterways. Their long, muscular bodies move with effortless precision, preying on #fish and crustaceans as they navigate the shifting currents.

Their decline is driven by rampant deforestation for palm oil expansion, hydroelectric dams blocking their migration, and the insatiable global demand for eels in the seafood trade and #pollution from #goldmining. In some areas, such as Malaysian Borneo, they have already been pushed to the brink of local extinction. Without urgent conservation measures, their migratory pathways will be severed, and their dwindling numbers may never recover. Take a stand against environmental destruction— be #vegan and #BoycottPalmOil #Boycott4Wildlife.

The Indonesian longfinned #eel is a sleek powerful #fish 🐟 Their long dorsal fin gives them agility. Threats include #goldmining and #palmoil #deforestation in #Indonesia 🇮🇩🇲🇾 #Malaysia. Help them and #BoycottPalmOil 🌴⛔️ #Boycott4Wildlife @palmoildetect https://palmoildetectives.com/2021/01/24/indonesian-longfinned-eel-anguilla-borneensis/

Appearance and Behaviour

Indonesian Longfinned Eels are sleek and powerful, with elongated bodies reaching over one metre in length. Their dorsal fin runs the length of their back, giving them remarkable agility in both fast-moving currents and stagnant waters. Their skin is smooth and mucus-coated, helping them slip through tight crevices and evade predators.

Their colouration varies from olive-green to deep brown, blending perfectly with the riverbeds they inhabit. Unlike their patterned relatives, these eels have plain, featureless skin, making them more vulnerable to illegal capture for the live eel trade. Their eyes are small but highly adapted to dimly lit waters, allowing them to detect prey even in murky conditions.

These eels are catadromous, meaning they spend most of their lives in freshwater before making an epic journey to the ocean to spawn. This extraordinary migratory cycle makes them highly sensitive to human interference, as dams, pollution, and deforestation disrupt the delicate balance of their existence.

Threats

Deforestation and habitat destruction for palm oil and timber

The destruction of riverine forests for palm oil plantations, logging, and industrial agriculture has devastated the freshwater ecosystems these eels rely on. As tree cover disappears, riverbanks erode, sediment chokes the waterways, and toxic agricultural runoff poisons aquatic life. Once-pristine rivers are now polluted, fragmented, and rapidly becoming uninhabitable.

The decline of this species in the Karabakan River, Borneo is thought to have been in response to extensive exploitation of the forest alongside the river and subsequent degradation of the freshwater habitat.

IUCN Red List

Hydroelectric Dams and Migration Barriers

Indonesian Longfinned Eels must migrate between freshwater and the ocean to reproduce, but dam construction, irrigation projects, and flood control structures block their ancient routes. In places like the Poso River watershed, these barriers have already reduced eel populations, and without free-flowing rivers, their life cycle cannot continue.

Overfishing and the Global Eel Trade

Eels are a highly sought-after delicacy in Japan, China, and South Korea, where their meat is prized in traditional cuisine. While Anguilla borneensis is not yet a primary target, their plain appearance and long fins make them indistinguishable from other commercially valuable species, putting them at risk of being indiscriminately harvested.

Mining and Mercury Pollution

Gold mining in Sulawesi and Borneo is poisoning freshwater ecosystems with mercury, which accumulates in the bodies of these eels. This toxic heavy metal weakens their immune systems, disrupts reproduction, and contaminates entire food chains, making survival even more precarious.

Climate Change and Oceanic Shifts

Like all migratory species, Indonesian Longfinned Eels depend on stable ocean currents and seasonal cues to guide their journeys. However, climate change is disrupting water temperatures, altering salinity levels, and shifting currents, all of which could lead to failed spawning events and population declines.

Diet

Indonesian Longfinned Eels are opportunistic carnivores, preying on small fish, crustaceans, aquatic insects, and worms. They are primarily nocturnal hunters, using their highly developed sense of smell to track down prey in dark, murky waters. Their sharp teeth allow them to grasp and swallow prey whole, making them formidable predators in their river habitats.

Reproduction and Mating

Like all anguillid eels, Indonesian Longfinned Eels undertake an extraordinary migration to reproduce. After spending years in freshwater, they embark on a final journey to the deep ocean, where they spawn once and die. The exact location of their breeding grounds remains a mystery, but scientists suspect they spawn somewhere in the Celebes or Maluku Seas.

Females lay thousands of eggs, which hatch into transparent leptocephalus larvae. These larvae drift on ocean currents for months before transforming into glass eels and making their way back into freshwater rivers. This complex lifecycle means they are highly vulnerable to environmental disruption, with any interference in their migration causing catastrophic population declines.

Geographic Range

Indonesian Longfinned Eels are found in Indonesia (Borneo, Sulawesi), Malaysia (Sabah, Sarawak), and the Philippines (Mindanao). They inhabit freshwater rivers, lakes, and streams, with their spawning migrations taking them through the Celebes Sea, Sulu Sea, Maluku Sea, and Makassar Strait. However, due to deforestation, dams, and overfishing, their range is shrinking, and they have already disappeared from parts of Malaysian Borneo.

FAQ

Are Indonesian Longfinned Eels endangered?

They are currently listed as Vulnerable on the IUCN Red List, but ongoing habitat destruction, migration barriers, and overfishing are rapidly pushing them toward endangered status.

Where do Indonesian Longfinned Eels live?

They inhabit freshwater rivers and lakes across Borneo, Sulawesi, and Mindanao, but their survival depends on access to the ocean for spawning. Without free-flowing rivers, they cannot reproduce, leading to local extinctions.

Why are eels important to the ecosystem?

As both predators and prey, eels play a crucial role in maintaining aquatic food webs. They help control fish and invertebrate populations, keeping river ecosystems healthy and balanced.

Are eels affected by deforestation?

Yes. Large-scale deforestation for palm oil, logging, and agriculture is one of the biggest threats to their survival. Pollution, sedimentation, and chemical runoff from gold mining and palm oil plantations have turned once-thriving rivers into dead zones.

Can Indonesian Longfinned Eels be farmed?

Unlike some other eel species, A. borneensis is not yet widely farmed, but with the collapse of other eel populations, they could become the next target for commercial exploitation. Protecting their wild populations is essential, be #vegan for them!

Take Action!

Indonesian Longfinned Eels are disappearing due to deforestation, dam construction, overfishing, and pollution. Their survival depends on protecting free-flowing rivers and pristine rainforests from destruction.Use your wallet as a weapon—#BoycottPalmOil #Boycott4Wildlife every time you shop. Fight for their survival before it’s too late.

Further Information

Arai, T., Chino, N., & Le Quang, D. (2013). Migration and habitat use of the tropical eels Anguilla marmorata and A. bicolor pacifica in Vietnam. Aquatic Ecology, 47(1), 57–65. https://doi.org/10.1007/s10452-012-9424-x

Inger, R. F., & Chin, C. K. (1962). The freshwater fishes of North Borneo. Fieldiana Zoology, 45(1), 1-268. https://biostor.org/reference/11287

Muthmainnah, D., Suryati, N. K., Mulyani, Y. S., & Pamungkas, Y. P. (2020). Fate of Anguillid eel fishery of Indonesia during the COVID-19 pandemic: Anguillid eel resource in Indonesia (Special Report). SEAFDEC/IFRDMD. https://www.researchgate.net/publication/349052661

Pike, C., Crook, V., Jacoby, D. & Gollock, M. 2020. Anguilla borneensis (amended version of 2019 assessment). The IUCN Red List of Threatened Species 2020: e.T198973A176496889. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T198973A176496889.en. Downloaded on 24 January 2021.

Wouthuyzen, S., Aoyama, J., Sugeha, H. Y., Miller, M. J., Kuroki, M., Minegishi, Y., Suharti, S. R., & Tsukamoto, K. (2009). Seasonality of spawning by tropical anguillid eels around Sulawesi Island, Indonesia. Naturwissenschaften, 96, 153–158. https://doi.org/10.1007/s00114-008-0467-6

You can support this beautiful animal

There are no known conservation activities for this animal. Share out this post to social media and join the #BoycottPalmOil #Boycott4Wildlife on social media to raise awareness

Indonesian Longfinned Eel Anguilla borneensis

How can I help the #Boycott4Wildlife?

Take Action in Five Ways

1. Join the #Boycott4Wildlife on social media and subscribe to stay in the loop: Share posts from this website to your own network on Twitter, Mastadon, Instagram, Facebook and Youtube using the hashtags #Boycottpalmoil #Boycott4Wildlife.

• Twitter
• Facebook
• Instagram
• WordPress
• YouTube
• Mail
• Mastodon

✓ Subscribed

2. Contribute stories: Academics, conservationists, scientists, indigenous rights advocates and animal rights advocates working to expose the corruption of the palm oil industry or to save animals can contribute stories to the website.

Wildlife Artist Juanchi Pérez

Read more

Mel Lumby: Dedicated Devotee to Borneo’s Living Beings

Read more

Anthropologist and Author Dr Sophie Chao

Read more

Health Physician Dr Evan Allen

Read more

The World’s Most Loved Cup: A Social, Ethical & Environmental History of Coffee by Aviary Doert

Read more

How do we stop the world’s ecosystems from going into a death spiral? A #SteadyState Economy

Read more

3. Supermarket sleuthing: Next time you’re in the supermarket, take photos of products containing palm oil. Share these to social media along with the hashtags to call out the greenwashing and ecocide of the brands who use palm oil. You can also take photos of palm oil free products and congratulate brands when they go palm oil free.

https://twitter.com/CuriousApe4/status/1526136783557529600?s=20

https://twitter.com/PhillDixon1/status/1749010345555788144?s=20

https://twitter.com/mugabe139/status/1678027567977078784?s=20

4. Take to the streets: Get in touch with Palm Oil Detectives to find out more.

5. Donate: Make a one-off or monthly donation to Palm Oil Detectives as a way of saying thank you and to help pay for ongoing running costs of the website and social media campaigns. Donate here

#Borneo #Boycott4wildlife #BoycottPalmOil #deforestation #eel #fish #ForgottenAnimals #goldmining #Indonesia #IndonesianLongfinnedEelAnguillaBorneensis #Malaysia #palmoil #Philippines #pollution #Sarawak #SouthEastAsia #Sulawesi #vegan #VulnerableSpecies

Knobbed Hornbill Rhyticeros cassidix

Knobbed Hornbill Rhyticeros cassidix

IUCN Red List Status: Vulnerable

Location: Indonesia (Sulawesi, Lembeh, Togian Islands, Muna, Butung) This vibrant, charismatic species is found only on the island of Sulawesi and its offshore islands in Indonesia. It inhabits lowland and montane rainforest ecosystems up to 1,800 metres above sea level, especially thriving in evergreen and tall primary forests.

Introduction

The Knobbed #Hornbills Rhyticeros cassidix announce themselves in gorgeous swirls of colourful feathers and beaks. They are currently listed as Vulnerable on the IUCN Red List in #Sulawesi #Indonesia due to rapidly accelerating #palmoil and #timber #deforestation, #hunting, and habitat degradation across Sulawesi. Despite being relatively common in some areas, this iconic #hornbill is suffering from extensive loss of lowland forest, fires, gold #mining concessions, and encroachment from palm oil plantations. As a seed-dispersing frugivore with unique breeding requirements, their survival is intrinsically linked to the preservation of large, undisturbed forest tracts. Their dramatic decline underscores the urgent need to halt industrial land use in Sulawesi’s remaining rainforest. Use your power as a consumer to #BoycottPalmOil #Boycott4Wildlife every time you shop.

https://youtu.be/_NVf1deSzDk

Knobbed Hornbills 🦜🌈 are stunning rainbow coloured #birds endemic to #Sulawesi #Indonesia. They are #vulnerable from #palmoil #deforestation and #hunting. Help them survive when you shop #BoycottPalmOil 🌴🪔🩸☠️🧐🚫#Boycott4Wildlife https://palmoildetectives.com/2021/10/30/knobbed-hornbill-rhyticeros-cassidix/

Knobbed #Hornbills 🦜🌈 need tree hollows to nest These intelligent #birds living in #Sulawesi #Indonesia are #vulnerable from #palmoil #ecocide and #poaching. Fight for them when you shop #BoycottPalmOil 🌴🪔🩸☠️🧐🚫#Boycott4Wildlife https://palmoildetectives.com/2021/10/30/knobbed-hornbill-rhyticeros-cassidix/

Appearance and Behaviour

Strikingly adorned with a large casque and vivid red-orange bill, the Knobbed Hornbill is unmistakable. Males have a prominent casque or ‘knob’ atop their bill and an unfeathered blue throat, while females sport an all-black plumage with a pale blue throat and lack the enlarged casque. Their broad wings and swooping flight pattern make them a spectacular sight to behold against the dense forest canopy.

These hornbills are highly vocal, using deep guttural calls to communicate across the forest. Pairs form long-term monogamous bonds and are typically seen together or in small family groups. Knobbed Hornbills are known for their territoriality and their habit of chasing off other birds and primates at fruiting trees, underlining their dominance within the rainforest canopy. Their daily routine includes long flights to feeding sites, often crossing fragmented landscapes to reach fruiting trees.

Diet

Primarily frugivorous, Knobbed Hornbills play a vital role in seed dispersal across Sulawesi’s ecosystems. They are particularly reliant on fig trees (Ficus spp.), which are a keystone food source for many tropical species. In addition to figs, they consume a wide variety of fruits, and are known to supplement their diet with insects, small reptiles, bird eggs, and even nestlings. Their foraging involves both perching and in-flight plucking of fruit, often from the upper canopy.

Their dependence on large-fruiting trees ties them ecologically to primary rainforest, making them especially vulnerable to habitat disturbance and deforestation. The decline of fig populations through forest clearing and degradation directly threatens their long-term food security.

Reproduction and Mating

Knobbed Hornbills nest in natural tree cavities high in the forest canopy, typically between 13 and 53 metres above ground level. Breeding depends on the availability of very large, old-growth trees—many of which are targeted for logging. The female seals herself inside the nest cavity with mud and regurgitated food, leaving only a small slit through which the male passes food during the entire incubation and chick-rearing period.

This remarkable nesting behaviour, while effective in predator avoidance, renders the female and chick completely reliant on the male’s continued presence and food provisioning. Any disturbance or death of the male during this time is likely to result in nest failure. Following hatching, the female remains sealed for several more weeks before emerging with the young chick.

Geographic Range

This species is endemic to Sulawesi and nearby islands including Lembeh, Togian, Muna and Butung in Indonesia. Historically widespread across Sulawesi’s forests, the Knobbed Hornbill is now increasingly confined to fragmented tracts of habitat due to extensive logging and agricultural conversion.

Although still described as locally common in less-disturbed areas, population declines of these hornbills have been recorded across its entire range. Many protected areas are poorly enforced, and forests in lowland Sulawesi have experienced staggering losses. Between 1985 and 1997, 89% of lowland forests were lost, and forest loss has only accelerated since then (FWI/GFW, 2002; Holmes, 2002).

Threats

Recent analysis has suggested that the Knobbed Hornbill may be declining at a rate approaching 40% over three generations based on recent and ongoing rates of habitat loss on Sulawesi (D. Holmes in litt. 1999, Kinnaird and O’Brien 2007).

IUCN red list

Palm Oil Deforestation

Sulawesi’s forests have been devastated by large-scale agricultural expansion, especially for oil palm and rice fields. Between 1997–2001 alone, forest loss accelerated to 36.1% per decade, wiping out vital hornbill habitat (Kinnaird & O’Brien, 2007). The hornbill’s strong dependency on large trees for nesting makes them acutely vulnerable to such losses.

Commercial Logging and Mining

Logging, both legal and illegal, has fragmented their habitat, making nesting success increasingly difficult. Additionally, gold mining operations in regions like Buton have destroyed critical tracts of primary forest, adding chemical and noise pollution to the ecosystem (Hamzah et al., 2023).

Fire and Climate Impacts

Severe fires, such as those in 1997, have reduced breeding success in subsequent years by decimating fig-bearing trees and altering microclimates within the forest (del Hoyo et al., 2001). Increasing climate instability will likely worsen fire frequency and intensity in coming decades.

Illegal Hunting for Bushmeat and their Casques

Hornbills are hunted for bushmeat and their casques are sometimes sold as ornaments. Although technically protected, enforcement is weak and hunting continues even within protected forests, especially near roads and settlements (Winarni & Jones, 2011).

Take Action!

Protecting the Knobbed Hornbill means safeguarding Sulawesi’s last remaining primary forests. You can help:

• Boycott palm oil and use your wallet as a weapon every time you shop.
• Support indigenous-led conservation on Sulawesi that focuses on protecting forest corridors and nesting trees.
• Pressure governments and companies to halt destructive mining and logging activities in Sulawesi.
• Make sure you don’t purchase goods made from hornbill and campaign against the deeply cruel illegal wildlife trade.
• Advocate for hornbill-safe agroecology and forest-friendly livelihoods in Indonesia.

FAQs

How many Knobbed Hornbills are left in the wild?

While no definitive census exists, the population is believed to be rapidly declining across Sulawesi, with many formerly common areas now devoid of breeding pairs. Fragmentation has isolated populations and reduced breeding success due to lack of nesting trees (Winarni & Jones, 2011).

How long do Knobbed Hornbills live?

In the wild, hornbills can live up to 30 years, with some individuals in captivity recorded beyond that. However, successful reproduction in the wild depends on stable territory, availability of fig trees, and access to nesting sites—conditions that are increasingly rare in Sulawesi’s degraded forests (Kinnaird & O’Brien, 2005).

Why are hornbills important to the rainforest?

Knobbed Hornbills are critical seed dispersers. Their diet of large fruits like figs means they spread the seeds of keystone species far and wide. Without hornbills, seed dispersal and rainforest regeneration slows, threatening the entire ecosystem (Kitamura et al., 2011).

What role does palm oil play in their decline?

Palm oil plantations are one of the biggest drivers of forest loss in Sulawesi. These monocultures replace biodiverse ecosystems with sterile landscapes, eliminating food sources, nesting trees, and pushing hornbills toward extinction. Avoiding palm oil is essential to saving this species.

You can support this beautiful animal

There are no known conservation activities for this animal. Share out this post to social media and join the #BoycottPalmOil #Boycott4Wildlife on social media to raise awareness

Further Information

BirdLife International. 2017. Rhyticeros cassidix (amended version of 2016 assessment). The IUCN Red List of Threatened Species 2017: e.T22682525A117182222. https://dx.doi.org/10.2305/IUCN.UK.2017-3.RLTS.T22682525A117182222.en. Downloaded on 08 June 2021.

Hamzah, A. S., Nasri, N., & Ardiansyah, A. (2023). Status, diversity, and feeding guilds of avifauna in the mining area. IOP Conference Series: Earth and Environmental Science, 1277, 012036. https://doi.org/10.1088/1755-1315/1277/1/012036

Martin, T. E., & Blackburn, G. A. (2010). Impacts of tropical forest disturbance upon avifauna on a small island with high endemism: implications for conservation. Conservation and Society, 8(2), 127–139. https://doi.org/10.4103/0972-4923.68914

Viseshakul, N., Charoennitikul, W., Kitamura, S., Kemp, A., Thong-aree, S., Surapunpitak, Y., Poonswad, P., & Ponglikitmongkol, M. (2011). A phylogeny of frugivorous hornbills linked to the evolution of Indian plants within Asian rainforests. Journal of Evolutionary Biology, 24(7), 1533–1545. https://doi.org/10.1111/j.1420-9101.2011.02285.x

Winarni, N. L., & Jones, M. (2011). Effect of anthropogenic disturbance on the abundance and habitat occupancy of two endemic hornbill species in Buton Island, Sulawesi. Bird Conservation International, 21(1), 28–36. https://doi.org/10.1017/S0959270911000141

Knobbed Hornbill Rhyticeros cassidix

How can I help the #Boycott4Wildlife?

Take Action in Five Ways

1. Join the #Boycott4Wildlife on social media and subscribe to stay in the loop: Share posts from this website to your own network on Twitter, Mastadon, Instagram, Facebook and Youtube using the hashtags #Boycottpalmoil #Boycott4Wildlife.

• Twitter
• Facebook
• Instagram
• WordPress
• YouTube
• Mail
• Mastodon

✓ Subscribed

2. Contribute stories: Academics, conservationists, scientists, indigenous rights advocates and animal rights advocates working to expose the corruption of the palm oil industry or to save animals can contribute stories to the website.

Wildlife Artist Juanchi Pérez

Read more

Mel Lumby: Dedicated Devotee to Borneo’s Living Beings

Read more

Anthropologist and Author Dr Sophie Chao

Read more

Health Physician Dr Evan Allen

Read more

The World’s Most Loved Cup: A Social, Ethical & Environmental History of Coffee by Aviary Doert

Read more

How do we stop the world’s ecosystems from going into a death spiral? A #SteadyState Economy

Read more

3. Supermarket sleuthing: Next time you’re in the supermarket, take photos of products containing palm oil. Share these to social media along with the hashtags to call out the greenwashing and ecocide of the brands who use palm oil. You can also take photos of palm oil free products and congratulate brands when they go palm oil free.

https://twitter.com/CuriousApe4/status/1526136783557529600?s=20

https://twitter.com/PhillDixon1/status/1749010345555788144?s=20

https://twitter.com/mugabe139/status/1678027567977078784?s=20

4. Take to the streets: Get in touch with Palm Oil Detectives to find out more.

5. Donate: Make a one-off or monthly donation to Palm Oil Detectives as a way of saying thank you and to help pay for ongoing running costs of the website and social media campaigns. Donate here

#Bird #birds #Boycott4wildlife #BoycottPalmOil #deforestation #ecocide #fire #fires #ForgottenAnimals #goldMining #Hornbill #Hornbills #hunting #Indonesia #KnobbedHornbillRhyticerosCassidix #mining #palmoil #poachers #poaching #SeedDispersers #seeddispersal #SouthEastAsia #Sulawesi #timber #vulnerable #VulnerableSpecies

Viral Istri Cek HP Suami Ada Video Mesum dengan Mantan

#Terviral - #Viral #Istri Cek HP #Suami Ada #Video #Mesum dengan #Mantan. Beberapa hari terakhir, #warga di Kabupaten #Luwu #Timur, #Sulawesi Selatan, dihebohkan dengan video mesum berdurasi 1 menit 6 detik yang diperankan seorang siswi SMP setempat berinisial AT. Video itu tersebar dari satu WhatsApp ke WhatsApp lainnya. Baca: Video Lagi Asyik Begituan di Ruang UKM Kampus Polisi tak tinggal diam dan bergerak cepat…

https://terviral.id/viral-istri-cek-hp-suami-ada-video-mesum-dengan-mantan/

Viral Video Siswi di Luwu Timur Ternyata Disebar Istri Pemeran Pria

#Terviral - Pemeran pria inisial A pada #video #syur dengan #siswi #SMP (sebelumnya ditulis SMA) di #Luwu Timur, #Sulawesi Selatan (Sulsel) ditangkap. Terungkap penyebar #viral video syur tersebut ternyata istri dari pemeran pria berinisial PB. "Tersangka inisial A adalah pemeran pada video tersebut, motif A menyimpan video rekaman adalah digunakan untuk tontonan pribadi," kata Wakapolres Lutim Kompol…

https://terviral.id/viral-video-siswi-di-luwu-timur-ternyata-disebar-istri-pemeran-pria/

Three dead after rioters set fire to several of #Indonesia’s regional parliament buildings in #Bandung and #Sulawesi.

“Five days of protests began in #Jakarta on Monday, sparked by reports that all 580 lawmakers receive a monthly housing allowance of 50 million rupiah ($3,075) in addition to their salaries.

The allowance, introduced last year, is almost 10 times the Jakarta minimum wage.”

#tootsea

https://www.npr.org/2025/08/30/g-s1-86456/3-dead-indonesia-regional-parliament-building

Time for #Sulawesi #hobbit cousin

https://cosmosmagazine.com/history/archaeology/sulawesi-ancient-stone-tools/