Introduction
Our first Expedition North Sumatra debuted in late August 2025. Like every new expedition, there is always an element of uncertainty regarding how our scouting trips will translate into a group tour. Unpredictable weather conditions can massively impact the activity levels of target species, while it is not uncommon for reliable forest trails to become inaccessible or destroyed within the space of a few months. It can also take time to refine the perfect itinerary, with the adequate amount of days at each location. For this expedition, we opted for a 50/50 split between highlands and lowlands (5 days each), attacking our targets with a diverse range of methods. Walking trails, hiking rivers, flipping debris, road cruising and road walking were all implemented on our quest to find as many species as possible.
To book Expedition North Sumatra in March 2026, click here!
Day 1 - Berastagi
Our group met near Kualanamu (Medan) on the first day, immediately driving around 2 hours up into the mountains of Karo land. Once we checked into our accommodation and had dinner, we met with Eddy and Radit, two local guides who would help us during our time in Berastagi.
We hit the upper elevations of Mount Sibayak volcano on the first night to target Gunalen's pit viper (Trimeresurus gunaleni), a Sumatran highland endemic to montane forests above 1,600 meters. We split up into two groups to cover more ground, and ended up finding a total of 6 Trimeresurus gunaleni. This was by far the most we have ever found in one night in this area, but unfortunately all juveniles and subadults. We were also surprised by 3 Sumatran mountain snakes (Elapoidis sumatranus) all found within 10 minutes during a period of light rain, the first of which was found directly underneath an ambushing T. gunaleni. When we found this species on our last scouting trip, it was one of the very first photo records. Unsurprisingly, we did not see a single other individual across all further nights in the area.
We also observed several of the area's iconic frogs and lizards during this first evening, but the only other snake seen was a fresh DOR (dead on road) Variable reed snake (Calamaria lumbricoidea).
In-situ of Elapoidis sumatranus and Trimeresurus gunaleni.
Sumatran mountain snake (Elapoidis sumatranus).
Simbolon mountain dragon (Dendragama schneideri).
Peter's bush frog (Philautus petersi).
Zhangixalus achantharrhena
Megophrys parallela
The largest of the 5 Gunalen's pit vipers (Trimeresurus gunaleni) seen.
Day 2 - Berastagi
The following day, we did some searching during the daytime but only found a freshly killled (DOR) Sumatran beauty ratsnake (Elaphe taeniura), a shame because it is one of our top targets here. The night started extremely slow as well, with not a single notable find until almost 2 hours in when Tomasz flipped a very rare lined blind snake (Ramphotyphlops lineatus) - a 'lifer' species for our entire team.
This discovery started a flipping rampage, whereby we turned over every single log and piece of trash possible - combining our efforts to lift huge parts of fallen trees which were embedded in the soil. This completely turned our night around, and we uncovered several remarkable reptiles within a short amount of time. Reptiles flipped under logs included several worm lizards (Dibamus sp.), an unknown skink (Sphenomorphus sp.), Padang reed snake (Calamaria abstrusa) and a Sumatran larut skink (Larutia sp.). A short walk at a waterfall also produced a large female Toba Lake pit viper (Trimeresurus sabahi toba) and many Splendid stream frogs (Hylarana fantastica), as well as a axanthic poisonous rock frog (Odorrana hosii). We discovered a population of this rare mutation on one of our previous scouting trips, and were very happy to see them again.
Padang reed snake (Calamaria abstrusa).
Lined blind snake (Ramphotyphlops lineatus).
Litter skink (Sphenomorphus sp.)
Worm lizard (Dibamus sp.)
Axanthic poisonous rock frog (Odorrana hosii).
Splendid stream frog (Hylarana fantastica).
The group enjoying a large Toba Lake pit viper.
Toba Lake pit viper (Trimeresurus sabahi toba).
Day 3 - Berastagi
The following morning, we woke up and drove to a nearby restaurant for a late breakfast. En-route, we were abruptly shocked awake by a big snake stretched across the road. We jumped out of the car to find a stunning Sumatran beauty ratsnake (Elaphe taeniura ssp.) which was full of attitude. This road is very busy at this time so we were incredibly lucky to find this snake before another vehicle ran it over. Later in the daytime, we did some flipping at a recreational forest and Marcus flipped a much larger Sumatran larut skink (Larutia sumatrensis). These short-limbed skinks have an incredibly elongated tail and body, moving much more like a snake than a typical scuttling lizard.
At night, we went back to the mid-montane (~900 meters over sea level) site and began with some road cruising in mixed forest-plantation land. The first snake encountered was a smooth slug snake (Asthenodipsas laevis), quickly followed by a very large Malayan banded coral snake (Calliophis intestinalis). We also cruised a keeled slug snake (Pareas carinatus) and a sunbeam snake (Xenopeltis unicolor). Along with these road-cruised finds, we caught a suspected dwarf reed snake (Pseudorabdion cf. longiceps) in a roadside drainage ditch, saw several more female Lake Toba pit vipers (Trimeresurus s. toba) near the streams and 2 oriental vine snakes (Ahaetulla prasina) sleeping beside the road.
However, the best find of the night was saved until last, when we decided to do a quick late-night walk at the high elevations (1,600 - 1,700m asl.). We focused on digging in leaf litter for fossorial species, but ended up uncovering a totally unexpected species. Crawling out of the leaf litter we were flipping was a beautiful sub-adult Sumatran leaf-nosed pit viper (Craspedocephalus andalasensis) - a highland-dwelling species which can be quite challenging to find.
Sumatran beauty ratsnake (Elaphe taeniura ssp.).
Sumatran beauty ratsnake (Elaphe taeniura ssp.).
Sumatran larut skink (Larutia sumatrensis).
Smooth slug snake (Asthenodipsas laevis).
Malayan banded coral snake (Calliophis intestinalis).
Keeled slug snake (Pareas carinatus).
Sunbeam snake (Xenopeltis unicolor).
Pseudorabdion cf. longiceps.
Oriental vine snake (Ahaetulla prasina).
Sumatran leaf-nosed pit viper (Craspedocephalus andalasensis).
Sumatran leaf-nosed pit viper (Craspedocephalus andalasensis).
Day 4 - Berastagi
On our final night of the trip, we focused on searching for two of our biggest remaining highland targets - Petronella's kukri snake (Oligodon petronellae) and the extremely rare Modigliani's nose-horned lizard (Harpesaurus modiglianii). While searching open submontane forest at around 1,500 meters for Harpesaurus, we found what was undoubtedly our second-highest priority lizard for the area: Manthey's mountain lizard (Gonocephalus lacunosus). This species is huge and incredibly impressive. We also found a reed snake which superficially seemed to be Calamaria abstrusa, but the venter was different and much closer inspection revealed it to be the short-tailed reed snake (Calamaria virgulata).
Meanwhile, our second group focusing on a nearby highland waterfall area where our local guides had seen Oligodon petronellae several times also had great bycatch success, finding an absolutely stunning sub-adult red-headed krait (Bungarus flaviceps) and finally finding a male Lake Toba pit viper (Trimeresurus s. toba). Unfortunately, the only Harpesaurus and Oligodon petronellae we saw were preserved specimens inside the forest reserve office, but still an incredible night to end our first stint at Berastagi.
Expedition Sumatra 2025 group pic.
Short-tailed reed snake (Calamaria virgulata).
Hayeki's crested lizard (Bronchocela hayeki).
Manthey's mountain lizard (Gonocephalus lacunosus).
Male Lake Toba pit viper (Trimeresurus s. toba).
Red-headed krait (Bungarus flaviceps).
Day 5
Just when we hoped that our luck had turned, and despite relatively good herping conditions, day 5 was undoubtedly our worst day of the trip. We saw some of our biggest targets DOR, namely a huge false cobra (Pseudoxenodon macrops), a Laotian bearded snake (Parafimbrios lao) and two juvenile Yunnan beauty ratsnakes (Elaphe taeniura yunnanensis) all dead on the road. Meanwhile, the only snakes we saw alive were a couple of checkered keelbacks (Fowlea piscator) in the daytime, and all 4 local species of slug snake at night (plus green vipers). Not that there's anything inherently wrong with slug snakes, it was quite impressive to see all the species in one night for the first time, but it hurt when every time we saw a target snake it was recently hit by a car (or ambulance, in this case). We did find one single new snake species for the trip, a banded wolf snake (Lycodon fasciatus).
Fowlea piscator & victim
Pareas cf. berdmorei
4 species of slug snake
Pareas macularius
Pareas margaritophorus
Lycodon fasciatus
Day 6
At this stage, the trip had fallen well below our expectations for what we hoped to have found by this point. It had been rainy and foggy almost every night since the trip began, and our luck with seeing the best snakes dead had been absolutely awful. Desperate to turn things around, we embarked on a huge hike to remote caves deep in the steep valleys, hoping to find a Yunnan beauty ratsnake (Elaphe taeniura yunnanensis) in one of them. Sadly, we only found one Lanna pit viper (Trimeresurus lanna) during the entire hike. To compound our misery, this day just happened to be the first cloudless and sunny day of the trip, meaning that we were absolutely cooking in the sun for hours, and the hike back to the hilltop at the end was undoubtedly a massive struggle for all involved. The beautiful views were great, but didn't quite make up for this.
Inspired even further by this failure, we didn't rest at all and immediately went out road cruising in the late afternoon. We saw nothing for a while, but right when we were about to call it and go to dinner, a huge dark snake appeared in the middle of the road at the high elevations. Running up to it, it spread a wide hood and turned to face us, showing itself to be an magnificent brown-banded mountain cobra (Naja fuxi), quite a rare cobra and one of our group's biggest targets for the expedition.
After dinner, we quickly got out road cruising again in the warm, dry conditions, and within minutes encountered an even larger mountain cobra, this time found directly between our two cars as we were crossing paths on the road. Having 10 people see the cobra on the road at the same time is a really rare occurrence enjoyed by all. Better yet, David found an alive Laotian bearded snake (Parafimbrios laos) later that night, another huge target for our group due to its rarity, similarities to the dragon snake (Xenodermus javanicus) and the bizarre scales on the face from which it gets its name.
Crossing streams
Steep hiking to caves
Northern Thailand scenery
Trimeresurus lanna
Naja fuxi seconds after encounter
Jace with Naja fuxi
Naja fuxi
The larger Naja fuxi
Parafimbrios lao
Parafimbrios lao
Day 7
The previous night was simply incredible and set the tone for the final 2 nights, whereby the weather had completely changed and all of a sudden it was hot and dry every day. We had officially reached the end of the rainy season, when dry weather brings everything out and the occasional rainstorms only boost activity even further.
Despite not getting up early, we cruised another two radiated ratsnakes (Coelognathus radiata) during the daytime, as well as a juvenile blue-eyed bamboo ratsnake (Gonyosoma coeruleum) in the late afternoon. After dinner, we immediately started finding even more snakes. While road cruising, we found another Gonyosoma coeruleum, multiple Chapa wolf snakes (Lycodon chapaensis) & banded wolf snakes (Lycodon fasciatus), another Yunnan green cat snake (Boiga cf. cyanea), and slug snakes galore. This streak culminated in ecstasy when a large, bright orange snake appeared in the middle of the road. Finally, we had found our first (alive) Yunnan red bamboo ratsnake (Oreocryptophis porphyracea pulchra).
Once road activity slowed down, we went out for a ridiculously productive stream hike, where we found two Lanna pit vipers (Trimeresurus lanna), by far our biggest blue-eyed bamboo ratsnake (Gonyosoma coeruleum) of the trip and a sleeping many-banded green ratsnake (Ptyas multicinctus). The latter is very rare in Thailand and was a huge target for those in our group who had come to Northern Thailand to see its beautiful colubrids. An absolutely incredible evening consisting of well over 10 species of snake and almost 30 total snake encounters.
Coelognathus flavolineatus
Gonyosoma coeruleum
Resort garden
Peak conditions
Injured Plagiopholis nuchalis
Slug snakes!
2 different Lycodon fasciatus
Boiga cf. cyanea
Chapa wolf snake (Lycodon chapaensis)
Gonyosoma coeruleum
Oreocryptophis!
In-situ Ptyas multicinctus
Oreocryptophis porphyracea pulchra
Ptyas multicinctus
Day 8
After such an incredible turnaround in fortunes, where we went from seeing everything good dead, to seeing everything good alive and in higher abundance than usual, it felt like our trip could not get much better. We were so wrong.
For the first time this trip, we took most of the day off. The mid afternoon was taken up by an incredibly heavy thunderstorm, and during the late afternoon we were consumed with our final day barbecue. By that point, the sun was out and drying everything up, making way for another night of absolutely prime herping conditions. Come sunset, we were out cruising and this time we were actively expecting some special encounters.
We began by doing road cruising passes on the highest elevations of the mountain, and merely a few minutes after it got dark, our guide Bank slammed on the breaks and started shouting "SLOWINSKII!!!". While leaning out the window shining the edges of the road, he had spotted our absolute number one biggest target for the expedition cruising along the edge of the tarmac. Moments later, our entire group was out of the two cars and marvelling at what is undoubtedly the best 'final night find' we have ever had across our many expeditions. The red river krait (Bungarus slowinskii) is one of the rarest elapid snakes in South-East Asia, with this only being the 6th confirmed record in Thailand. It is a very large snake, and despite being extremely venomous, certainly one of the most docile snakes you can encounter in its cold, submontane forest habitat.
With the best final night find under the belt, we continued herping with the mentality that anything else is a bonus at this point. Not even 10 minutes later, we spotted a bright red snake rapidly moving across the road. Unsure of what it was, we jumped out of the car to find a huge red coral snake (Sinomicrurus cf. annularis) on the road. This was another of our biggest targets which we had only seen DORs of so far, and this was possibly the best individual ever. Strangely, it had a orange band on its head as opposed to the usual white band. It was also double the size of any individual we had seen before, dead or alive. Simply ridiculous.
Over the next hour, we saw several more snakes, including the bulkiest Lanna pit viper (Trimeresurus lanna) we have ever laid our eyes on, more wolf snakes, and of course many slug snakes. We wrapped up extra early so we could all appreciate, photograph and release the amazing snakes we had encountered that night, since some people had to leave early the next day. A simply incredible end to the expedition. A flurry of fantastic finds, checking off most of our biggest targets - both for guides and guests.
Group pic
JB on barbecue duty, legend
Prime conditions, again.
Something special...
This!
Trimeresurus lanna
Lycodon chapaensis
Must be something good...
Yep!
Bungarus slowinskii
Annulated coral snake (Sinomicrurus cf. annularis)
Day 9 (extension)
While Expedition Northern Thailand had officially ended, some of the guests extended for an extra day (with the guides) as the herping had been astronomically successful, the good conditions seemed like they would continue, and there was still one very special snake which had eluded us in the first 8 days. Sure enough, Jordi, Platon and Niklas went for hike to the high elevations of the mountain and during a cloudy spell at midday, Platon spotted a juvenile black-striped green ratsnake (Ptyas nigromarginata) - the very snake we were hoping for the most - basking on top of an exposed shrub.
As we were split up at the time, we could not believe that this had happened and were convinced they were joking when they told us they have found "nigromarginata". This snake is truly one of the most beautiful animals to exist on this planet, both in juvenile and adult form. They only occur at the very highest elevations of the mountain in Northern Thailand, and are very rarely seen, even if you spend weeks searching. Everything had come together with perfection - the perfect script.
Later that afternoon, we visited a local snake keeper who had recently caught a Harold Young's supple skink (Lygosoma haroldyoungi), one of the most incredible lizards in the world. While it was a shame we were not able to find one of these ourselves during this expedition, it was still great to see and interact with this crazy skink in person. We all enjoyed it greatly.
Despite rain in the late afternoon, we went out for a quick final night of herping together and focused on highlands. We turned up several of the species featured many times this report, along with another (much smaller) coral snake (Sinomicrurus cf. annularis) with the typical colour morph. This made it 4 back to back days of sensational sightings.
Ptyas nigromarginata
Ptyas nigromarginata
Lygosoma haroldyoungi & Platon
Small rain showers
Coral snake
Sinomicrurus cf. annularis
And that concludes our first ever Expedition Northern Thailand. A rollercoaster experience which saved the very best until last. Looking back at our species list, we missed very few of the 'showstopper' species occurring in the area, finding the two biggest snake targets (B. slowinskii and P. nigromarginata) which we had highlighted on the expedition page prior to the start of the expedition. One could say it cannot get better than this, but we have said that before and were proved wrong...
To join our next Expedition Northern Thailand (10th - 19th October 2025), click here!
