Herping

Bornean keeled green pit viper — the snake most people actually connect with.

Borneo holds somewhere around 180 described frogs and comfortably more than 250 reptiles, and unlike the birds and the mammals, a large share of them can be found by one person with a head torch walking slowly along a stream. That is what makes herping here different: it is the one branch of Bornean wildlife watching where effort converts into sightings almost linearly, and where a good night can produce twenty species inside a kilometre. It is also almost entirely nocturnal, almost entirely weather-driven, and rewards patience over distance. This is a guide to where to go, how the nights actually run, and what to look for. Every species mentioned here has a page in the field guide — frogs, snakes, lizards and reptiles generally.

What herping in Borneo is actually like

The first thing to understand is that the day is the wrong half. A daytime walk in lowland forest gives you skinks on the leaf litter, a flying lizard gliding between trunks, an angle-headed lizard alert on a trunk and gone before you have focused on it, and not much else. Nearly everything worth finding comes out after dark, and the productive window is roughly 7pm to midnight, with the first two or three hours after nightfall the best of it. Herping in Borneo means committing to night walks, and it means being reasonably relaxed about being wet.

The second is that streams are the organising principle. Most Bornean frogs breed in or beside running water, and a huge proportion of the reptile interest — pit vipers, keelbacks, water skinks, bent-toed geckos — sits within a few metres of the same water. A single small forest stream walked slowly, in the water rather than beside it, will out-produce ten kilometres of trail. The technique is genuinely slow: torch on the vegetation at knee-to-head height either side of the channel, then on the rocks, then on the surface, then repeat. People who cover 300 metres in two hours find more than people who cover three kilometres.

The third is eyeshine and its limits. Frog eyes throw back a dull orange-white, spider eyes a hard blue-green, and after an hour you sort them without thinking. Snakes, though, have almost no useful eyeshine — you find them by shape, by the wrong sort of line across a branch, or by the pale coil sitting motionless above a pool. Vipers in particular are ambush animals that do not move when your torch hits them, which is exactly why they get walked past and occasionally trodden near.

And the fourth is sound. Frog choruses tell you where to spend the night before you have seen anything, and they are species-specific enough that an experienced guide will name six or seven species from the car park. A recording app and a bit of homework goes a long way here, though the calls are far less documented than the birds.

Set expectations accordingly, because there is a real gap between what people come for and what they get. Snakes are the draw — almost everyone who books a herping trip here is thinking about pit vipers, kraits and the dragon snake — and snakes are also the thing you see least of. A good night at a good site in the wet season is fifteen to thirty species of frog, a few geckos, and, if the night is kind, one or two snakes. Plenty of visitors do a week of solid night work and come away with four or five snake species, and that is a normal result rather than a bad one. The frogs are what fill the notebook; the snakes are what you remember.

Snakes, which are why most people come

Snakes are found rather than looked for, and no site guarantees them. The realistic strategy is to be out on a lot of nights near water and to walk night roads where the surface holds heat, since a warm road after dark is one of the few places a snake will be out in the open. Green pit vipers are the most reliably encountered group: Keeled Pit-viper coiled above a stream at head height is close to a set piece at the right sites, and the Sumatran Pit Viper replaces it in some areas. Beyond that, cat snakes and bronzebacks work the vegetation, the Oriental Whip Snake is the one common diurnal find, the Mangrove Snake is a black-and-gold speciality of riverbanks and mangrove, and the Dragon Snake — three keeled ridges down a matt-black back — is the one everybody wants and almost nobody gets. At the top of most people's lists sit the elapids: the Red-headed Krait, the Blue Coral Snake and, for a certain kind of visitor, King Cobra. None of them are findable to order.

What raises the rate is not cleverness but hours, and the right ground. Undisturbed lowland forest with a stream running through it beats anywhere else, second growth and forest edge produce more than people expect, and a night with rain in it beats a dry one. Beyond that it is arithmetic: the people who come home with a good snake list are almost always the people who did the most nights.

Frogs, which are what you'll actually see

Frogs are the dependable half of the trip and the reason a poor snake week is still a good week. The fauna divides fairly cleanly by habitat, and knowing the divisions is most of what makes a night productive.

Tree and flying frogs sit on vegetation over standing or slow water, which is why pools and roadside ditches inside forest are worth more than fast streams for this group. Wallace's Flying Frog is the headline, with fully webbed black hands and feet it uses to parachute between trees; the Harlequin Tree Frog hides orange and black flash markings in its webbing, and the File-eared Tree Frog is a big, angular, yellow-eyed thing with a bony ridge behind the eye that once seen is never confused.

Torrent and stream frogs want the opposite — fast, rocky, oxygenated water. This is where the rock skippers sit on spray-washed boulders and semaphore with a hind foot, a visual signal that works where calling does not because the water is too loud. The Hole-in-the-head Frog belongs here too, and is one of the genuinely strange animals of the island: it hears through an open recess in the skull rather than an external eardrum, and calls partly in ultrasound.

Litter and horned frogs are the ones you nearly step on. The Bornean Horned Frog is a dead-leaf mimic the size of a fist that sits still and calls a metallic honk from the forest floor; the slender litter frogs are smaller, commoner and much harder to name.

Toads and oddities round it out — the Giant River Toad is a genuinely large animal on riverside rocks at night, the slender toads are long-legged and delicate and nothing like a European toad at all, and the Tree Hole Frog calls from inside water-filled tree cavities and tunes its call to the resonance of the hole it is sitting in.

Lizards, turtles and crocodiles

Lizards divide by when you can find them rather than by when they are active. The Draco flying lizards, the angle-headed lizards and the shrub lizards are all diurnal, but the day is the worst time to look at them — they see you first and are gone before the camera is up. The trick is that they sleep out in the open, perched on the tip of a thin sapling or a twig over the trail, and a torch at night finds them motionless and close enough to photograph properly. Skinks are the exception, working the leaf litter by day and out of sight after dark. Geckos are the other half of a night walk: the bent-toed geckos are a large and still-unsettled group on rocks and trunks, the parachute geckos have skin flaps along the flanks and tail and flatten against bark until they are invisible, and the Cat Gecko — slender, cinnamon, curls its tail like a cat and moves with the same deliberation — is a favourite well out of proportion to its size. Monitors sit at the far end of the scale: Rough-necked Monitor in forest, water monitor along every river and drain in the region.

Turtles and crocodilians are a small list but a real one. Saltwater Crocodile is present through the Kinabatangan and most coastal rivers and is the one animal here that genuinely constrains where you put your feet after dark; the Malaysian False Gharial is the rarer and far more interesting sighting. Among the turtles, Spiny Hill Turtle turns up on wet forest floor at night and Painted Terrapin is a critically endangered coastal-river species that most people will only ever see at a hatchery.

Where to go

Kubah National Park, Sarawak

The single best-known herping site in Borneo, and the one that does not need a big budget. Forty minutes from Kuching, and the draw is the frog pond on the Waterfall Trail — a small area of shallow water and overhanging vegetation that in the wet season holds a dozen or more species within a fifty-metre radius, Wallace's flying frog among them. The park runs an evening frog walk, night access is straightforward, and the surfaced road up to the summit gives easy torch work along the verges. If you have three nights in Borneo and want frogs, spend them here.

Danum Valley

Primary lowland forest, the full lowland herpetofauna, and the streams to work it in. Night walks from the field centre and the trails along the Segama tributaries produce horned frogs, torrent frogs, the fanged frogs, bent-toed geckos and a reasonable pit viper rate, and the night drives out along the access road add the road-crossing snakes. The advantage over the Sarawak parks is that the forest is undisturbed and the species list is correspondingly complete; the disadvantage is cost and the need to book well ahead. Good herping guides are available here but need requesting specifically — the default guiding is aimed at mammals and birds.

Kinabalu Park and Poring

The montane herpetofauna, which shares very little with the lowlands — Kinabalu Horned Frog, the Kinabalu slender toads, the montane litter frogs and a set of high-altitude bent-toed geckos found nowhere else. The Silau-Silau trail and the streams around park headquarters are the working ground, and it is cold and wet enough at 1,500 metres that a lot of visitors underestimate it. Poring, on the lower eastern side of the same park, sits at around 500 metres and gives you the lowland set instead, which makes the two together an unusually efficient pairing. Lupa Masa, the jungle camp in the forest above Poring, is a long-standing favourite with herpers for exactly that reason: rough accommodation, a river running through it, and frogs from the doorstep.

Kinabatangan River

Riverine and floodplain species rather than forest ones, and the easiest place in Sabah to see reptiles without walking. Night boat trips along the banks and the oxbow lakes pick up sleeping mangrove cat snakes, water monitors, and crocodile eyeshine, and the tributaries hold puff-faced and dog-faced water snakes. Frog diversity is lower than in hill forest — this is swamp and disturbed edge — but the sightings come easily, which makes it a good first stop while you are still getting your eye in.

The rest of Sarawak, and Tawau

Gunung Gading, near Lundu, has good stream work and is usually combined with Kubah on a Kuching-based trip. Bako adds the mangrove and heath-forest species — a different set again, with monitors, mangrove snakes and the coastal skinks. Lambir Hills near Miri has hill dipterocarp forest and a long list of stream frogs, and Gunung Mulu puts limestone into the mix, which brings cave geckos and the karst specialists with it. Over in Sabah, Tawau Hills Park is the underrated one: hot springs, several good streams, cheap access from Tawau, and a species list that holds up against sites costing ten times as much.

When to go, and when to be out

This is the one part of Bornean wildlife watching where the advice inverts. Birders and mammal watchers are told to favour the drier months; herpers should do the opposite. Frogs breed on rain, and the wetter stretch — broadly the northeast monsoon, roughly November to February in Sabah, with the heaviest rain in Sarawak from November to January — is when the choruses are loudest and the diversity on a given night is highest. Some species are explosive breeders that are essentially invisible for months and then present in hundreds for a few nights after a downpour, so the difference between a wet week and a dry one is not marginal.

Within that, the unit that matters is the individual night rather than the month. Rain during the afternoon or early evening, followed by a break, is the ideal — the forest is saturated, the pools are refilled, and the animals are out. A clear, dry, moonlit night after a dry week is the poorest combination there is, at any time of year. If you have a flexible itinerary, spend the nights after rain in the forest and take your rest days when it has been dry.

Hour by hour: out by 7pm, best from 7.30 to about 10.30, tailing off after midnight though the snake activity holds up later than the frogs. Dawn is not a thing here in the way it is for birds. The realistic constraint is stamina — four nights in a row of five-hour walks is harder than it sounds, and most people do better alternating hard nights with easy ones than trying to do every night at full intensity.

Kit, and the safety and ethics of it

The head torch is the whole game. Bring two — a bright one for scanning and a weaker one for close work — plus more batteries than you expect to use, because cold-soaked cells in a wet forest do not last their rated time. A handheld torch alongside the head torch helps enormously with snakes, since the offset beam picks up shape and shadow that a light beside your eyes flattens out. Wellingtons or proper river shoes rather than boots: you will be in the water. Leech socks earn their keep. A hand lens is worth carrying for the small frogs, and if you are photographing, a diffused flash matters far more than an expensive lens.

On safety: Borneo has genuinely dangerous snakes — king cobra, kraits, the pit vipers, and the sea snakes offshore — and the sensible policy is simply not to handle anything. Nearly every serious incident involves someone picking a snake up. Watch where your hands go on stream banks and above head height on vegetation, since vipers sit at exactly the height you would grab for balance. Know how far away the nearest hospital is before you start, which at Danum or Mulu is a long way.

On ethics: amphibians absorb through their skin, so if you must handle a frog, do it with clean wet hands and briefly, and never with insect repellent or sunscreen on them. Better still, photograph in place. Amphibian chytrid fungus has been recorded in Southeast Asia, and boots and gear that have been in one catchment can carry it to another — cleaning and drying footwear between sites is a small effort against a real risk. Put anything you move back exactly where it came from, roll logs back, and do not cut vegetation for a photograph. And be careful what you publish: the illegal trade in Bornean reptiles is fed partly by online sightings, so precise localities for the scarce and collectable species are best kept off the internet.

Species you won't see without going looking

Most visitors to Borneo will see a water monitor and hear a chorus of frogs from the lodge. The three below are different, and each is a reason on its own to build nights into an itinerary.

Wallace's Flying Frog

The famous one

A large bright green tree frog with enormous fully webbed hands and feet and black flanks, described from Sarawak by Alfred Russel Wallace, who watched one parachute down from a tree and could not quite believe it. The webbing works: it can glide fifteen metres or more between trees and steer while doing it. It breeds in foam nests over water and comes down to pools and wallows to do it, which is why the frog ponds at Kubah and the wallows in lowland forest are where people find it — and why a dry week can mean not a single one.

Bornean Horned Frog

Leaf mimic

A heavy, flat, fist-sized frog with pointed projections over each eye and a sharp snout, patterned and veined so precisely like a dead dipterocarp leaf that people photograph the ground it is sitting on without noticing it. It sits on the litter beside forest streams, waits for anything smaller than itself to walk past, and gives a loud metallic honk that carries much further than you would expect. Widespread in hill forest across Borneo — Kubah, Danum, Poring and Tawau Hills all produce it — but always found rather than looked for.

Red-headed Krait

The one to hope for

The snake most Bornean herpers would put at the top of the list, and one of the most striking elapids anywhere — a long, slender, glossy blue-black animal with a fine pale stripe down each flank and a head and tail of bright coral red. It reaches close to two metres, lives in undisturbed lowland forest, and is strictly nocturnal, spending the day out of sight and hunting other snakes after dark. Highly venomous and, like the other kraits, extremely disinclined to use it — the encounters people describe are of an animal that keeps moving and wants nothing to do with you. It is thinly spread and genuinely scarce, so it is found by being out on a lot of nights in good forest rather than by going anywhere in particular.

Worth reading up on in the same category: the Dragon Snake, matt black with three keeled ridges down its back, semi-aquatic and rarely found; the Blue Coral Snake, electric blue-flanked with a red head and tail and venom unlike any other snake's; the Hole-in-the-head Frog, which hears through a hole in its skull and calls above the range of human hearing; the Bornean Flat-headed Frog, which has no lungs at all and breathes entirely through its skin in fast Kalimantan streams; and the Malaysian False Gharial, the narrow-snouted crocodilian of peat swamp and blackwater rivers.

Planning a trip around this

Shape. A herping-first trip looks nothing like a birding one. Two bases worked hard beat five visited briefly, because the value is in repeat nights on the same stream in varying weather rather than in ticking sites. A common and effective Sarawak version is a week out of Kuching — Kubah with a couple of nights at Gunung Gading and a day at Bako. The Sabah version pairs Kinabalu Park with Poring or Lupa Masa for the altitudinal split, then adds Danum or Tawau Hills for lowland forest.

Guides. A herping guide is a different specialist again from the bird and mammal guides, and there are fewer of them. What you are paying for is someone who knows which pool at which site is holding water this month and can name a slender litter frog in the hand, which is a genuinely hard skill. Say what you want when you book — a general nature guide will do their best and will find you a fraction of what a herper would. The tour operators page lists who runs what.

Logistics. The Sarawak parks are cheap, close to cities and can be done independently; night access rules vary by park, so check before you assume you can walk after dark. Danum and Mulu need booking well ahead and cost accordingly. Wet-season travel means occasional road and flight disruption, which is the price of the good frog nights.

Expectations. You will get wet, you will find more frogs than anything else, and the snakes will come when they come. The nights that produce nothing are part of the arithmetic — the ones that produce a dragon snake or a Wallace's flying frog on a leaf a metre from your face are what everyone remembers.

Pick the locations you want to visit and the species you want to look for, then send the finished plan straight to an operator.