| 1 | Smooth slug snake |
A nocturnal snake commonly found on low bushes, or resting calmly on giant rainforest leaves dripping with rainfall. The smooth slug snake (Asthenodipsas laevis) reaches a maximum of 60cm, and resides in both primary and secondary forest. This is a classic snail-slurping snake, with the classic snail-slurping features, like an unbalanced jaw designed for gripping shells and sucking the snails free simultaneously.
Smooth slug snakes vary massively in colour, from orange to stone grey to grey with neon blue tinges like above. But one consistent feature is thin, dark bands encircling their entire body. The bands may be fainter in some individuals, but they’re always identifiable. Each of the bars is separated by 4 or 5 normal scales. Another ID feature which is commonly found but not always is a pale stripe extending all the way down their spine (like above). Their eyes are round and black rather than vertical.
How common they are varies significantly. On the Malaysian peninsular, they’re relatively sparse, yet there’s plenty of sightings in northwest Borneo near Kuching, the largest city in the Malaysian state of Salawak. Meanwhile, their cousin on Borneo is the dark-necked slug snake (Asthenodipsas borneensis), which also possesses the thin bands, but has a huge black patch on its neck which you can’t possibly miss.
| 2 | Borneo python |
A glistening tank of a python which lurks in the swampiest Borneo rainforests and waits patiently in ambush, cunningly moving its eyes and little else to detect mammals that stray past. The Borneo python is part of the blood python crew, a group of 4 closely related species sold widely on the international reptile trade. Blood pythons are popular because of their immobile ways and easily satisfied diet. They mostly prey on mammals, including simple mice and rats, and they take down their prey using a brutal lunch, knocking the wind out of their prey.
The Borneo python (Python breitensteini) is found exclusively on its namesake island, covering the entire landmass, from Malaysia and Borneo in the northern half to Indonesia in the south. The other “blood pythons” include the Sumatran short-tailed python (Python curtus) found in the west of Sumatra. Then there’s the blood python proper (Python brongersmai), found in eastern Sumatra, peninsular Malaysia, and southern Thailand. Finally, there’s the recently discovered Myanmar short-tailed python, found far further north.
Borneo pythons share the island with reticulated pythons, but the latter is far longer (can be over 6 metres), and looks far thinner as a proportion of their length. The Borneo python is one of the thickest, bulkiest serpent brutes ever.
| 3 | Borneo pitviper |
A pitviper endemic to the island of Borneo, occurring nowhere else. Borneo pitvipers were originally part of the giant Trimeresurus green pitviper genus, but were reassigned to the smaller Craspedocephalus group, which currently has 14 members. Part of the reason is that they’re never green. This snake ranges from grey to tree trunk brown to a cheesy orange, with vertical pupils and complex forest patterns. Though dangerous, this snake is no brute, with an all-time record length of just 87.4cm.
Craspedocephalus borneensis is a flexible pitviper. They’re often found on branches or coiled up on juicy green rainforest vegetation, yet are equally comfortable on the forest floor. This snake inhabits Borneo’s lower altitude areas, appearing at 25 metres up to 1130 metres, or at least that’s the maximum recorded so far. Their confirmed prey includes Draco maximus, AKA the great flying dragon, AKA the giant gliding lizard. This was hunted on a branch 4 metres away from a small stream, but the pitviper regurgitated the lizard when it spotted the scientists.
Borneo is full of remote forests and villages, and exactly how many people Craspedocephalus borneensis kills is unknown. However, a 2005 study found that their venom contains PLA2s with anti-coagulant and edema-causing activity. Like most pitvipers, this species probably causes local symptoms and spontaneous bleeding, but death less commonly.
| 4 | Sabah keelback |
Another species endemic to the island of Borneo, occurring nowhere else. The Sabah keelback, or Hebius flavifrons, is one of Borneo’s more recogniseable snakes, due to their snowy white snouts. Their body is grey-green with irregularly spaced white bands, which are broken and not fully encircling. Then you reach their snout, and it’s like they’ve just dipped their mouth in a carton of milk. This contrasts against some black facial markings and large round eyes.
Hebius flavifrons averages at 54cm, with one third consisting of the tail, and is commonly found resting on low shrubs. This species is found from 0 to 700 metres in altitude, and often appears near streams. Sabah keelbacks are regularly encountered in Borneo. They’re not shy and secretive, and are regularly found close to streams poking their heads into the air inquisitively. Somehow though, barely any research has been conducted on them. Their diet is said to include tadpoles, frogs and eggs, though no prey has been identified down to the species level.
Another Hebius member, the white-browed keelback of Hong Kong, also preys on small amphibians. Supposedly Sabah keelbacks are spotted regularly swimming in Borneo’s rivers with their heads poking out of the water.
| 5 | Striped dwarf tree snake |
This non-venomous species is mainly found on Borneo, but also on the Natuna islands west of Borneo, and the Philippine island of Palawan. The striped dwarf tree snake (Lycodon tristrigatus) can reach 65cm, and is most commonly found in forests, where it moves by night. It seems to enjoy coiling itself into a random ball of coils, as the image above shows.
This snake is skilful at coiling around uber-thin branches, and weaving along fallen tree trunks without the claws of gravity dragging it down to the forest floor. Slithering vertically up trees is one of its specialities, as this snake has excellent gripping abilities. It can slither up trunks covered with moss or those with great strips of bark peeling away from them.
Nothing is known about the striped dwarf tree snake’s diet. We do know that the closely related Lycodon nympha of India eats eggs, by slicing the shells open using enlarged teeth, while constricting them, then drinking its contents.
This snake was once dubbed Dryocalamus tristrigatus, but the Drycolamus genus (which had 6 members) was decided in 2016 to actually be non-existent, and this species was switched to the huge Lycodon genus containing the wolf snakes. A paper argued in 2020 that Drycolamus was a legitimate group, as Drycolamus had a wider head, more protruding eyes, and more keeled scales, versus completely smooth scales for Lycodon members. The debate continues, but for now this species remains a Lycodon member.
| 6 | Schmidt’s reed snake |
This species is endemic not just to Borneo, but the northern tip of Borneo. This is Sabah state, a Malaysian region which is especially abundant in tropical rainforest and is sparsely populated in comparison to its size, with most humans concentrating in towns along the coasts. The interior is a vast paradise of exotic creatures, and Schmidt’s reed snake is one of the least researched.
We know a few facts; Calamaria schmidti is one of the more iridescent snakes in the world, with a clear rainbow shimmer when light is shined on it. An earthworm was found in one’s stomach, which is similar to other members of the Calamaria genus (which has a giant 66 members). In a cross-section they have a cylindrical body shape, and they have few actual patterns.
Mount Kinabalu National Park is one place you’ll find this secretive serpent. This is one of the only places on Earth where their population density seems fairly high. But even this hotspot is covered with forests, and with the accumulated layers of decades of forest mulch, which Schmidt’s reed snake loves to burrow through. If you find this snake, then you are an official accomplishment unlocker. Schmidt’s reed snakes appear under rotting logs as well, and are mainly found at altitudes of 1370-1570 metres.
| 7 | Dark-headed Sabah ground snake |
This non-famous snake lives in virtually the same areas as Schmidt’s reed snake. It’s endemic to Sabah state in northern Borneo, and has the highest density of sightings in Mount Kinabalu National Park. Mount Kinablu is the highest mountain not just in all of Borneo and Malaysia, but between the Himalaya and New Guinea (whose highest mountain reaches 4509 metres). The national park was established in 1964 and declared to be a world heritage site in 2000. It’s a high, jungled place, as even the Kinabalu Park Headquarters lie at an altitude of 1,866 metres.
As for the snake that clings to these mountainous slopes, Stegonotus caligocephalus is a shiny snake with few patterns, that ranges from brown to an oily blue-black. It can exceed 1 metre, and its belly is yellowish. Stegonotus caligocephalus has only been found at altitudes of 1300 metres and higher. So far, our only dietary knowledge was an attempt at preying on a gecko, namely the Balu bow-fingered gecko.
The Stegonotus family is fairly widespread, with 24 members. The most common member is easily the slatey-grey snake (Stegonotus australis) of Australia, but the dark-headed Sabah ground snake has become stuck in one narrow region of Borneo. Borneo is the furthest west the Stegonotus genus reaches; none exist in peninsular Malaysia, Sumatra or Thailand.
| 8 | Everett’s kukri snake |
Part of the huge 88 member kukri snake genus, and one of the more mysterious. Everett’s kukri snake (Oligodon everetti) is a non-venomous creature incapable of ending your life. This isn’t a mountainous species; it prefers lowlands ranging from 0 to 1000 metres. Primary forests are its domains, and it’s reported to feed on reptiles and reptile eggs.
Overall, this is a species which has existed for millions of years, with endless millions of individuals existing in that time engaging in all sorts of wacky forest exploits. Yet in 2024, we can only tell you a handful of facts about it, mostly relating to their physical appearance.
To find this species, search for a bright orange belly contrasting sharply against a browner, blotchier back. There’s no gradual fading in, but a sharp delineation between the two colours. Everett’s kukri snakes have round pupils with a dark brown stripe running diagonally through the eyes.
Everett’s kukri snakes (Oligodon everetti) are mainly found in eastern Borneo. You won’t find them in northwest Borneo near the populous Malaysian city of Kuching, but they do appear in Sabah state and southeast Borneo in the Indonesian portion of the island. The jeweled kukri snake is another name for this species, because of its richly detailed patterns.
| 9 | Malaysian spotted keelback |
A water-loving snake which reaches a maximum of 100cm, and poses no threat to humanity. To find this snake, you should dock in Borneo and venture to a forest stream. The problem: there’s thousands upon thousands of forest streams in Borneo…
Luckily, this species is fairly common. The Malaysian spotted keelback (Xenochrophis maculatus) is significantly more widespread than some of our list. Java is out of bounds for this snake, but they successfully inhabit Sumatra, peninsular Malaysia, extreme southern Thailand, and Borneo, which is probably their main stronghold. Malaysian spotted keelbacks are most likely to be spotted in sunny weather after a previous day of heavy rains
This snake sometimes moves in a stop-start fashion; it slithers very slowly and cautiously one moment, then rapidly speeds up and covers large distances. Two Malaysian spotted keelbacks were even seen dancing together once, which was possibly a male-female seduction ritual, but possibly for fun – who knows.
Big eyes are one of their classic characteristics, which look like they would pop like bubbles if you touched them. This is one of Borneo’s frog-eating snakes, with a confirmed meal being the Malayan giant frog (Limnonectes malesianus). Malaysian spotted keelbacks are most closely related to the striped keelback (Xenochrophis vittatus), found in Java.
| 10 | Painted mock viper |
A common species on all of Borneo, as well as Sumatra and peninsular Malaysia. This is a mildly venomous snake, which delivers its toxin elixir only via rear fangs and is virtually harmless to humans. Painted mock vipers are usually found near rivers in forest areas, typically along the shore within a few metres. This snake is capable of fishing, by waiting along the shore with its neck coiled in an s-shape, and unloading the coil the moment it sees a shadow move past in the depths.
This snake is variable in appearance, with beige, brown and even red morphs appearing. It’s an intricately patterned snake, and the most complex patterns run directly down their spine, bordered on each side by pale stripes.
Psammodynastes pictus only reaches a maximum of 55cm, versus 77cm for its cousin the common mock viper (Psammodynastes pulverulentus). The painted version also lives further south generally, while the common mock viper reaches Taiwan and even northeast India, while also inhabiting Borneo and coexisting with their cousin.
A study from Malaysian Borneo found that common mock vipers prefer smaller, shallower streams, and appear more commonly away from streams, while painted mock vipers were more common near deeper rivers, and were always within 150cm of water. The two species had subtly differing habitats to avoid heavy competition with each other.