Into the heart of the Danum

Into the heart of the Danum

Borneo – click here to listen to the awesome sounds of the jungle

Danum Valley sunrise

Danum valley sunrise

The journey to the Danum

While in Borneo, my friend and colleague Phil Lewis received an interesting email. It seemed that researchers from Australia who are friends of people we know had just been into the Danum valley in central Sabah for ten days, and in their own words had “cleaned up” meaning they had seen quite a lot of amazing animals. Everything from elephants to the tiny lemur-like Tarsiers as well as all sorts of frogs and reptiles. One thing that demanded our attention was finding Flying Frogs. So far in Western Sabah all of our efforts to find these elusive frogs had come up blank, mostly because suitable habitat is severely lacking- but the Danum has it in abundance. So, with some last-minute rushing about we booked the next flight we could manage and soon were jetting our way to the small Oil Palm town of Lahad Datu, the gateway to the Danum Valley.

Not knowing quite what to expect, George- one of the researchers had told us we had to prove affiliation with a university or other institution to gain access to the Danum, and that we had to visit the field office and register and hope we would be let in. So with this in mind we gazed down on huge fields of Oil Palm, even from our height it stretched far into the distance right to the horizon. One wonders what is left for the wildlife.

Touching down in Lahad Datu after the hour long flight we were confused as to where to go. The Danum Valley field office was somewhere nearby, but where? After being sent literally all over town by bad directions from locals we finally found the place. A nondescript wooden door had the logo of the valley on it, and we entered and were greeted by a lady behind a desk. She smiled and asked us how long we wanted to stay for, and what we needed while we were there. Every question meant yet another cost to pay. Fifty Ringgit just to enter the park.

“Do you want to eat meals we cook?” She asked

“No, we will cook for ourselves…”

“That will be ten Ringgit a night then”


“Do you want to camp? Only ten a night to hire a tent…”


“But seventy-eight a night for the site!”

“Not a chance since the Danum Valley hostel is only three Ringgit extra”

“Our official transport is full, and will not be back for three days. You might have to hire a charter vehicle to the Danum”

“How much?”

“Three hundred and fifty!”

“Double ouch!”

“Do you have a camera?”

“Yes, we do”

“It’s ten per camera and fifty per video camera”

“Ummm, we only have one camera”

This went on for quite a while, she was helpful and reduced the cost as much as she could. Eventually a brand new Toyota pickup truck arrived to take us to the Danum Valley

I was dead tired and elected to sprawl out over the back seat while Phil posted himself in the front. As we hit the dirt road, the ‘driveway to the Danum’ the vehicle rattled and banged its way all the way to the checkpoint where a guard sat in an office to control the boom gate. The boom was a red and white candy-pole that had a rope going from the long end via a pulley into the office and the short end had a bucket of rocks as a counterweight. Soon it lifted up to grant us entry to the Danum Valley reserve and we continued to explore every pothole the road had to offer. Big piles of elephant dung marked the passage of elephant herds most of the way to the research center. Two hours after setting out we arrived at the Danum Valley research center’s reception.

The Danum Valley is a hub of research and small scale tourism. One of the last patches of good lowland jungle it is home to such animals as Clouded Leopards, various other smaller cats, Orangutans, Gibbons, Leaf Monkeys, Rhinos, Elephants, Tarsiers, Loris and an enormous variety of reptiles, birds and amphibians. In the complex there is a restaurant, hostel, ranger station, Danum information center and various research laboratories.

I crashed in a bed while Phil vanished into the jungle. After a few hours I woke up and went out to find a researcher working on his PhD within the Danum Valley. Graham is his name, and very friendly and helpful he showed me around the Danum Valley research center’s grounds.

“Come and see where the Wallace’s Flying Frogs hang out” he said.

So we walked up a short path through the forest and he pointed out a small clay bank with a puddle about the size of a coffee table against it. A pig wallow, the local swine population use it to roll about in and cover themselves in mud. In doing so they have dug it out a little and created a mud puddle.

Next up we sloshed our way through mud and leaves (this was to set the scene for the entire Danum trip!) and down another path. We crossed a small creek and walked up a clay bank. Graham stopped and pointed into the jungle to the right.

“This is where we found a few Reindwart’s Flying Frogs- the only place in the Danum we have found them. Somewhere in here is a forest pond they breed in. Do you know the call they make?”

I didn’t, so he explained further.

“They sound like a burst from a machine gun, whereas the Wallace’s sounds like a Woodpecker. Anyway, I need to be getting back now. Good luck.”

So the long-awaited night finally came and since Phil had returned we decided to head off to find these frogs. On the way we stopped at the dining area. A loud shrill scream announced the presence of an owl. On the tennis court below two large brown owls sat on the fence. With obvious “ears” they were the resident pair of Buffy Fish Owls. One landed on the court itself and shuffled about chasing frogs and insects, gulping them down and screeching loudly. For some reason these birds as they waddled around under the lights reminded me of comical, animated feather dusters. One thing that concerned me a little was the lack of rain, since this day was the first dry day in a while. As we set out, the heavens opened and within seconds we were totally drenched. On the path we could hear the frogs all through the forest.

Treehole Frogs are common in the Danum

A male Treehole Frog in his hole

One that both Phil and I wanted was the curious Tree Hole Frog (Metaphrynella sundana) which by all accounts seems abundant in the Danum. Unusual among frogs it seeks out holes in trees that are full of water, so long as the tree is less than four inches in diameter. There, the male makes musical piping notes to draw females in for a look. Despite being very common, no records of their tadpoles exist so far. We had seen and even filmed them in infra-red elsewhere, but could not get a colour picture as when the lights went on each time they would retreat, This time we were lucky as this male sat in his hole for pictures, and we even carefully lifted him out for some photographs and returned him to his hole. We came back to check on him later and he was obviously unharmed as he called with all the enthusiasm of earlier.

Eventually we reached the pig wallow, and to our surprise there were no Wallace’s Flying Frogs, only one Harlequin Flying Frog (Rhacophorus pardalis), supposedly the most common of the ‘flying’ frogs in the Danum. Not as famous as the other species, it is brown with darker bands, gold eyes, red fingers with a leopard pattern of black spots on yellow on the lower sides. It is however regarded as a “proficient glider” and, like the other Flying Frogs has extensive webbing on the fingers and toes that act like parachutes to allow the frog to make a controlled, angled descent when it jumps from a tree.

Harlequin Flying Frogs are the most likely flying frog you will find in the Danum

So we elected to try the other spot in the Danum Graham vaguely knew about. A frog called from the treetops, so Phil and I tracked to to the very tree it was calling from. Not a Flying Frog, it was a Bush Frog of sorts, a Philautus. But it was far too high to see. In the distance we heard a strange popping sound, one knock, then another and another, rapidly accelerating then stopping abruptly. We followed the sound right to its source. A tree had fallen, and where the root mass had been was a large depression was left to fill with water. Frogs were all over it. Mahogany Frogs (Rana lactuosa) sat in burrows in the remaining root mass, calling their soft “whooping” call, their black sides contrasting sharply with their rich red backs. Puddle Frogs (Occidozyga) floated about, croaking away, and sitting in twigs over the pond, File Eared Tree Frogs (Polypedates otilophus) hunched over seemingly offended by us turning up to their party uninvited. Several Harlequin Flying Frogs joined in on leaves and branches over the water. But we could not see the culprit of the knocking call. Another one called from high up in the trees- too high to even see. But I did glimpse the white belly and yellow sides of one. Finally, our first sighting of a Wallace’s Flying Frog. And what a frog it was. Phil and I audibly gasped at the size of it. Around 100mm long, it was bright green on top with yellow thighs, feet and hands. In dire need of good photographs, I climbed up the root mass and reached out and gently picked him up. Immediately he spread those enormous webbed hands like a pair of paddles, wrapping them around my finger. I now had the problem of getting down the murderously slippery mud and clay covered root mass. Passing the frog to Phil I did manage to get down. But what an amazing frog, such vivid green and yellow. Inside the palms was a lovely black smudge, no doubt a “Flash colour” when shown with the bright yellow to warn predators that it might be distasteful. After a few pictures it launched off into the bush, not to be seen again that night.

The Wallace’s Flying Frog is common in the Danum

A burst of rapid machine-gun like taps indicated the Reindwart’s Flying Frog was here although rare in the Danum. True to its species it hates the ground even more than the Wallace’s and calls from very high up. We couldn’t even pinpoint exactly where it was, so infrequently did it call. Much smaller than the Wallace’s, it looks very similar but has lovely blue in the palms rather than yellow and black. With no more to photograph for now, we headed back to the Danum research complex and over the river into the jungle on the other side. Searching about yielded a series of invertebrates. I felt something on my leg, and looked down in time to see a matchbox sized spider crawl up my leg and without any provocation it sank its fangs into my skin. Instant pain followed and other than a little bit of swelling nothing much else could be said about it. Leeches were abundant in the Danum jungle.

These snakes are incredibly thin

Almost every leaf in the Danum had a five centimeter long Tiger Leech on it. They would arch their bodies out like a long twig, sitting perfectly still. As soon as our scents reached them they came to life, waving their front ends about, looping towards us over the ground or simply dropping down from above. Every few minutes we pulled them off our skin If you like leeches, the Danum is the place! Blood, sweat and moisture from the forest ran down my ankles freely and at one point I could feel it sloshing about in my shoes. The forest floor in the Danum was muddy clay covered in leaves. More times than we could count,

Phil and I stepped on a leaf mass and slid, sometimes standing up for a meter or two, other times landing with our legs in the air.

At one point I stopped and looked up for no particular reason and saw a very slender snake in the foliage. We coaxed it down and had a good look at it. Roughly a hundred and twenty centimeters long it was dark brown with red saddles. Between each saddle was a dark spot. Some of the saddles had a red blotch at the bottom. The eyes were silver. It was a Slender Cat’s Eye Snake, Boiga drapiezii. A lizard-eater it searches the canopy for its prey. The other part of the common name comes from the cat-like eyes. We left it to go about its business.

The Slender Cat’s Eye Snake is a striking animal

One animal of interest was a small number of Pseudo scorpions we found, they were everywhere in the Danum. Much like a long legged scorpion with reduced claws, instead of a sting they have a structure much like a car antenna coming from their rear. Totally harmless to humans I decided to see what defense they actually have. I sized up a 70mm specimen and touched it with a twig. It pointed its rear skywards and lunged with its tiny claws. Soon I smelt a peculiar smell, like vinegar. It suddenly became overpowering. The vinegar-like smell had a pungent rotting aspect to it. Even though I had not touched the animal, the smell sank into my skin up my right arm. I scrubbed my arm and hands in mud, and even when I got back to the kitchen and doused them in detergent and even soy sauce the smell did not go away. Phil had made the mistake of actually handling one and experienced similar issues.

The next afternoon we woke up and headed out into the forest. Something we had to see was the waterfall, there is one main one in the Danum Valley. Hiking through the leeches and mud we took a wrong turn and ended up back where we started. An hour was lost, so we tried again and actually found the right path. Up ahead, elephants could be heard breaking trees and grumbling. Knowing that they could be dangerous here in the Danum, we cautiously peered around trying to see them. We couldn’t, but knew they were very close. With extreme caution we crept past and continued up the track. We reached the waterfall with only an hour to spend before being forced back to base to beat the darkness. With no light, food or enough water staying the night was not an option. During that hour we found a medium sized toad in a most unusual position. Above one of the falls it sat on a horizontal branch asleep. I pulled the branch closer while balancing carefully, but it leaped into the water and vanished. Phil cursed while I scanned the water below. It surfaced near the rocks on the edge, so I jumped into the water and swam over to it. Picking it up it felt strange. Hard and slightly prickly it sat in my hand without a struggle. Little wonder it didn’t need to struggle as a cloud of one of the most disgusting smells came off it and went right up my nose. It was like holding a living dog poo. I was revolted. Phil was still on top of the falls calling for me to hang onto it. I had to move it away from my face. It leaped out of my hand and vanished once more. Surfacing again it swam into a cave just above the water line. Phil was livid, so we both tried to reach in and all I could find was a turtle. Feeling its back as it shuffled around I could not extract it safely, and I didn’t know what type it was and whether or not it was a biting species, so I left it. With Phil in dark spirits at not photographing the stink toad it was a quiet walk back.

Back at base, we spoke with some more of the Danum researchers. Elephants came up in the discussion.

“Look out for those elephants” said one of the researchers.

“How dangerous are they?”

“They are extremely dangerous. Treat them with caution to say the least. An Australian lady was gored to death here in Sabah a few weeks ago, she got too close and took a picture which startled the animal and it killed her. One of our scientist is lucky to be alive. He accidentally got in between a mother and her calf. She attacked and he jumped in between the buttress roots of a large tree. She was so enraged she reared up and tried to crush him but could not get her feet between the roots to get him. We even had a car here in the Danum rolled by an angry elephant while the team was in the jungle. They came back to find it on its roof all smashed up. If they see you at night with a light, they will attack. So you must be very careful.”

Well, after that we were very careful not to encounter any pachyderms in the Danum forest.

Microhyla petrigena – we only saw it in the Danum

That night we had to re-visit the pig wallow. Stan, a researcher from the Czech Republic but living on the Indonesian side of Borneo came along. More interested in mammals than anything else we did see a whole heap of animals getting about the forest. The Short-Tailed Deer were out in force, munching on the grass around the complex and I did spot a cat of sorts. Larger than a house cat it was too fast for identification. In a stream I picked up the eye shine of a big frog. Phil went over to check it out and we discovered it was a Giant River Frog (Limnonectes leporinus). On a leaf nearby, I spotted a tiny frog, smaller than a fingernail. Only half an inch long it was an adult Microhyla petrigena and beautifully coloured at that. Such a small frog is so hard to find and it was a blessing to have it on a leaf, easy to see.

At the wallow itself, we found three Wallace’s Flying Frogs which was odd considering their absence there the night before, plus some more Harlequin Flying Frogs. We captured one Wallace’s Flying Frog and set up the camera on a tripod with two wireless flashes. I made some adjustments to the flash output and we were ready to fly, or at least ready for the frog to. Phil took up position behind the camera and I persuaded the frog to jump. On the first go, Phil got the best shot of the night. After some more pictures the frog went back to his branch. Phil and Stan went off by themselves, leaving me to try and film the other frogs in the branches. Wallace’s Flying Frogs are tentative callers at best, but these ones were too shy to call for the camera. So I went off exploring by myself and found four new frogs for the list. The first was a Guardian Frog (Limnonectes finchi) which lays its eggs in the leaves where the male guards them. When they hatch they attach to his back for him to carry to water to complete their development.

A Wallace’s Flying Frog in action

The Sticky Frog

Second was a small toad, a native Bufo divergens. Light brown in colour it sported a slight dark marbling on the back. Next up was a small Sticky Frog, Kalophrynus heterochirus. Wedge-shaped with a light stripe down the side it, like other Sticky Frogs will puff up and exude a nasty glue from the skin which is strong enough to glue a predator’s mouth shut.


The last new species for the night was a Banded Tree Frog (Rhacophorus fasciatus) which looks similar to the Harlequin Flying Frog but with a more angular snout, less webbing and less colour. Eventually I found Phil again and he announced he had seen a Wagler’s Pit Viper (Trimeresurus wagleri) high in a tree near the Danum research center. Lovely light blue-green it had a white and red stripe along the sides of its face. A dangerous snake it is very closely related to the Rattlesnakes, and like them has foldable fangs, heat sensing pits on the face and a short temper. A bite causes necrosis and loss of muscle, often with lifelong deformities for the victim. I selected a large stick and gently prodded the snake which obligingly wrapped itself around the stick so I could lower it to the ground. We found a nice tree to photograph it on before release back to where it came from. It struck out at us numerous times, but sat still for the most part for the pictures.

Banded tree frog

The Rough Guardian Frog

Bufo divergens

The dangerous Wagler's Viper

Next to the Danum research center was this Wagler’s viper in a tree

The next and final day in the Danum we woke up at lunch time to make one last attempt at the waterfall. We took a wrong turn and ended up taking the long path. Phil wanted to look at the canopy lookout, so I let him check it out while I sat on the forest floor on a tree root. Seeing a tree nearby moving I looked closer as there was no wind. Leaves fell to the ground. Knowing there was an animal up there I looked closer and saw, much to my delight a furry red primate- something I knew was in the Danum but I didn’t expect. I called out:

“Hey Phil, I see an Orangutan!”

Phil practically teleported down to the ground and we headed towards the tree for a better look. Phil was barely able to contain himself as we got closer. When we reached the tree the female looked down at us. A baby peered through her fur with inquisitive eyes, then hid its face again. Too far away for a photo, I tried in vain to get good footage. We gave up and enjoyed the moment. The female became curious, stopped eating and climbed down a few metres to have a closer look. Suddenly it started to “rain”.

“Check it out, she’s taking a slash!” exclaimed Phil.

When she had finished (luckily we were out of the line of fire) she continued munching away at tender twigs and leaves until we left.

Not long after, we heard Gibbons calling loudly, the hooting sound carrying a long way through the jungle. A screech and some commotion up ahead marked a troop of Red Leaf Monkeys. Angry at our intrusion they scattered, turning back every now and again to express their distaste at our arrival. One even jumped from a high tree into the undergrowth with a loud crash. Further along we heard a deep rumble and trees snapping. Elephants were nearby. We froze in dread, but luckily we did not see them, nor did they see us.

At another point, an unknown animal growled at us from the treetops. Stopping to look for it had no result.

River Toad

We reached the waterfall well behind schedule and ran out of light fast. I just managed to film some of it as well as the weird torrent fish scraping the thin organic layer on the rocks with their strange sucker mouths. The toad was back on the exact branch it was on the day before over the waterfall, so we managed to photograph it, much to Phil’s delight. I explored a branch of the river. While standing and admiring the cascades, I felt something move over my foot. I looked down to see a White Nosed Watersnake (Amphiesma flavifrons). Mottled and dark it had a few white spots and an incredibly obvious white spot on the forehead. We both got a fright and it vanished into a crevice before I could do anything.

As it got dark, I emptied the blood from my shoes after another leech attack and we explored the cascades and creeks. Not finding many species new to us, we did see lots that we were familiar with already (see the sections on the Crocker Range) but Phil had gone ahead at one point and found one of the most beautiful frogs I had ever seen. Reminiscent of a Poison Dart Frog, it was an unrelated species Rana picturata- the Spotted Stream Frog which was common in the Danum’s streams. Black and covered in almost metallic gold and orange spots it was indeed a living jewel.

The exquisite Spotted Stream Frog was found in the Danum’s streams, especially around debris piles

As we left to get back to base the heavens opened and torrential rain fell down. The path quickly went under cascading rivulets of water. We trudged through the mud and leaves washing down the hillside, and as we neared the end of the walk, a strange white rat-like creature ran over the path. Pure white and fluffy it was shaped much like an American Opossum. It bolted off into the jungle. Later Stan told us it was a type of spineless Hedgehog. A little further along I spied a Leopard Cat. It jumped onto a log and sat there patiently while I filmed it. As I stopped recording it jumped off the log and vanished. It was now time to head back indoors as we had to catch the transport back to the airport first thing in the morning.

Wagler’s Viper

File Eared Tree Frog

Puddle Frog

Stay tuned for reports of future visits to the Danum

2 comments on “Into the heart of the Danum

  1. Nathan on said:

    Wait for Phil’s upcoming report on the Crocker Range where he will fill you in on the details of the awesome variety of frogs we found there, many of which we also saw in the Danum.


Leave a Reply

Your email address will not be published. Required fields are marked *



HTML tags are not allowed.