Explorations of an Ecologist

Saturday, 10 March 2018

Borneo - Part 13 (Gomantong Caves, travel to the Danum Valley)

Introduction
October 3, 2017 - Day 1 on Mount Kinabalu
October 4, 2017 - Day 2 on Mount Kinabalu
October 5, 2017 - Poring Hot Springs
October 6, 2017 - Day 3 on Mount Kinabalu
October 7, 2017 - Day 1 at the Crocker Range
October 8, 2017 - Day 2 at the Crocker Range, Kota Kinabalu
October 9, 2017 - Klias Peatswamp Forest Reserve
October 10, 2017 - Arrival at Sepilok
October 11, 2017 - Sepilok
October 12, 2017 - Sepilok, travel up the Kinabatangan River
October 13, 2017 - Kinabatangan River
October 14, 2017 - Gomantong Caves, travel to the Danum Valley
October 15, 2017 - Day 1 at the Danum Valley
October 15, 2017 - Night Hiking in the Danum Valley

October 16, 2017 - Day 2 at the Danum Valley

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October 14, 2017

Located off the grid, the Borneo Nature Lodge generates their electricity from solar. A tower outfitted with solar panels had been built in the center of the lodge area, to maximize the solar radiation that it could acquire by reaching above the trees. This tower doubles as an excellent vantage point to watch for birds passing through the trees. As it was our last morning here, I decided to bird from the tower for an hour or two just after dawn.

View from the tower - Borneo Nature Lodge, Kinabatangan River, Sabah, Malaysia

This was a good decision, and even though the birding was a little slow at times, occasional individuals would pass through the nearby trees. I love watching an area come alive at dawn and the tower provided a perfect vantage point. Two of the species I identified were new ones for me; they both happened to be Borneo endemics as well. A trio of Charlotte's Bulbuls (E) passed by, and two Yellow-rumped Flowerpeckers (E) also made appearances. While sitting up on the tower I took advantage of the surprisingly good cell reception and called home, catching up with mom and dad who were enjoying a beautiful autumn evening in Cambridge.

We enjoyed our last breakfast at the lodge, said our goodbyes, and loaded into the boat for our final trip. This time we would not be searching for wildlife - it was just a quick jaunt down the river to Sukau where our bus was waiting for us. The plan for the day was to make the long drive from Sukau (#7 on the below map) to the Danum Valley, which is #9 near the bottom of the map. Along the way we would stop at the impressive Gomangtong Caves (#8) for a couple of hours.

Following a short drive through the countryside we approached the Gomantong Caves. Within the immediate vicinity of the caves a large swath of forest had been protected, preventing the land from the insatiable saws of the logging industry and the resulting oil palm plantations that have taken up so much of southeast Asia.

We followed a boardwalk through a section of forest that eventually opened up near the main cave entrance. Along the way several impressive centipedes were seen, while a Black-crowned Pitta (E) called from somewhere off of the path.

Near the entrance to the cave in an open area, several of these skinks were easily seen. I believe they are Common Sun Skinks (Eutropis multifasciata) but I could be mistaken - resource materials for the skinks of southeast Asia are not exactly easy to come by on the internet.

Common Sun Skink (Eutropis multifasciata) - Gomantong Caves, Sabah, Malaysia

The caves themselves were nothing short of impressive. Upon entering the massive chamber of the first cave, a rush of cool air blew past us, while the high pitched twitters of thousands of bats and swiftlets filled the air. The distinct aroma of guano was immediately obvious, and the odorous substrate was 10-20 feet deep in areas. Stepping on the guano would instigate a dozen or more cockroaches to instantly appear in the boot impression left behind. The total biomass in these caves must be incredible, between the bats, swiftlets, but especially the cockroaches.

Gomantong Caves, Sabah, Malaysia

The walls were covered in cockroaches of varying sizes. For someone who becomes a little squeamish in situations like this, the caves must be like something out of a nightmare. But for a naturalist like myself, I was in a guano-filled heaven!

Cockroaches - Gomantong Caves, Sabah, Malaysia

Three species of swiftlets nest in these limestone caves, each named based on the colour and composition of their nests. We observed the Mossy-nest and Black-nest Swiftlets on the walls of the cave, but the White-nest Swiftlets nest in a different part of the cave system. These swiftlets are virtually indistinguishable in flight, especially in the low-light conditions afforded in the cave, but the nests are quite distinctive. These swifts produce the nests that are harvested and used to produce birds-nest soup, an expensive delicacy in southeast Asia.

Mossy-nest Swiftlets - Gomantong Caves, Sabah, Malaysia

The White-nest Swiftlets create the most coveted nests since mud or organic materials are not incorporated into the nest, but the nests of Black-nest Swiftlets are also harvested; these nests are considered lower quality because mud is incorporated by the swift into the nest. The Mossy-nest Swiftlet's nests are not harvested due to the high amount of organic material added by the swift. The harvest of swift nests is a regulated activity in Sabah, to prevent indiscriminate collecting. At certain times of the year, licensed harvesters will climb up precariously built scaffolding to collect newly created nests.

Bats and Mossy-nest Swiftlets - Gomantong Caves, Sabah, Malaysia

Any sick or injured swift or bat does not last long on the floor of the cave. The cockroaches make quick work of any unfortunate organism, such as the below swiftlet which was on the railing beside the boardwalk.

Cockroach and swiftlet sp. - Gomantong Caves, Sabah, Malaysia

Of course, no cave is complete without rats. This is a Müller's Rat, the most common rat found in limestone caves in Borneo.

Müller's Rat - Gomantong Caves, Sabah, Malaysia

While the cave was fascinating to explore I think each one of us was a little relieved to exit and breath some fresh air. It was now close to noon and the day was heating up, though we still found a few birds as we retraced our steps along the boardwalk through the forest. Along the way some of us had good but brief views of a Hooded Pitta, while we also found a pair of Black-naped Monarchs and a White-crowned Shama (E) that cooperated nicely alongside the boardwalk.

We enjoyed the air conditioning of the bus as we embarked on the long drive to the Danum Valley. Most of us took advantage of a little bit of shut-eye on the drive. After all, we were not missing much out the window except for vast tracts of oil palm plantations.

Finally we turned off the main road and began driving towards the Danum Valley. This corner of Sabah contains some of the best quality remaining primary forest in Borneo. The protected area includes 438 square kilometres of untouched lowland dipterocarp forest, which is in turn surrounded by managed forest that includes teak plantations interspersed with intact forest.

Our bus driver made a great spot as we rumbled along the gravel road. It was a big male Bornean Orangutan! We all awoke relatively quickly and stumbled from the bus to have a better look at the ape.

Bornean Orangutan pit stop

The Bornean Orangutan was a "flanged" male; referred to that way because of the fatty cheek-pads on the sides of the face. Only the mature males exhibit these flanges, which help demonstrate dominance and which females find highly attractive on a male. Bornean Orangutans with flanges show higher levels of testosterone than unflanged males.

By the time that my camera had defogged itself, he had retreated behind some vegetation and a clear shot was no longer an option - this was the best I could do. Regardless, we were all pretty happy to have had such good looks at a flanged male Bornean Orangutan.

Bornean Orangutan - entrance road to the Danum Valley, Sabah, Malaysia

We were all a little more attentive for the remainder of the drive, as we entered the reserve and were suddenly surrounded by pristine forest. Along the way we observed our first Bearded Pig, followed by a Red Muntjac which paused along the side of the road long enough for most people to have good looks through their binoculars. Just before dusk we rolled into our accommodations for the next three nights - the beautiful and decadent Borneo Rainforest Lodge. The skies opened up upon are arrival, but we were met by the lodge staff with towels and welcome drinks, which hit the spot after a long afternoon on the road.

That night we set out for a night drive with our guide, Azmil, who would be with us for our three days in the Danum Valley. The bed of the truck had been outfitted with two rows of padded benches where we sat facing the middle, while Azmil stood and faced forward while scanning around with a powerful halogen spotlight tied into the trucks electrical system. If he spotted something, he signaled to the driver with his light. He had different signals for different commands, such as stop, go backwards, go forwards slowly, and continue onward. Despite the rain that was at times heavy, we had a moderately successful drive thanks to the excellent spotting ability of Azmil. Some of the highlights included Palm Civet, Sambar Deer, Malay Civet and a File-eared Treefrog (Polypedates otilophus). Eventually due to heavy rain we were forced to head back early, but it had been a nice introduction to the Danum Valley.

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October 16, 2017 - Day 2 at the Danum Valley

Wednesday, 7 March 2018

Borneo - Part 12 (Kinabatangan River)

October 16, 2017 - Day 2 at the Danum Valley

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October 13, 2017

The following morning dawned warm and misty, as is typical for the lowlands in Sabah. After a cup of coffee our group departed for our early morning boat cruise, the first of three boat trips we would take today. The remnants of mist were rapidly burned off by the rising sun as we motored upriver.

Almost immediately we began spotting wildlife along the banks of the Kinabatangan. First up was a group of Proboscis Monkeys, feeding on the leafy foliage lining the banks of the river. This was our first extended look at this charismatic species, and we soaked in the excellent views.

Proboscis Monkey - Kinabatangan River, Sabah, Malaysia

Proboscis Monkeys exhibit a specialized digestive tract consisting of multiple stomachs, each containing bacteria to help break down the tough cellulose material in the leaves which dominate their diet. Feeding on leaves allows Proboscis Monkeys to utilize this abundant food source, a trait also shared with the langurs.

Proboscis Monkey - Kinabatangan River, Sabah, Malaysia

Proboscis Monkeys live in harems containing several dozen individuals, including one alpha male who enjoys exclusive "breeding rights" with the females. The alpha male is easily identified by its substantial nose, as well as by his permanently erect, bright red penis; both these features are used to demonstrate vigour and strength to other Proboscis Monkeys.

At around two years of age, young males leave the group and join up with other bachelors, living with them for a number of years. Usually by around 10 years of age, a male is strong enough to challenge an alpha male in another harem. If successful, the usurper takes over that male's harem. Infanticide is commonly seen with Proboscis Monkeys; often this is done by the new alpha male as it attempts to remove the former alpha's offspring from the group.

Proboscis Monkey - Kinabatangan River, Sabah, Malaysia

While we were busy watching the Proboscis Monkeys our guide Ben made an incredible spot with a Buffy Fish-Owl, tucked away in a dark corner of the understorey several dozen meters back from the edge of the river.

Buffy Fish-Owl - Kinabatangan River, Sabah, Malaysia

Pacific Swallows are the local flavor along rivers in Borneo and we saw many throughout the morning.

Pacific Swallow - Kinabatangan River, Sabah, Malaysia

Hornbills are always exciting birds, appearing like prehistoric dinosaurs as they cruise past. Both Black Hornbill and Oriental Pied-Hornbill made appearances during our morning cruise.

Oriental Pied-Hornbill - Kinabatangan River, Sabah, Malaysia

As we rounded a bend along the river one of the guides spotted a female Orangutan feeding on fruits high up in a riverside tree, and seconds later a youngster was also seen a few meters away. Needless to say this caused a great deal of excitement as they were our first wild Bornean Orangutans!

Bornean Orangutans - Kinabatangan River, Sabah, Malaysia

The next twenty minutes were just magical. The Bornean Orangutans fed on figs out in the open and with binoculars we could see every detail. The adult female appeared to be pregnant, leading us to believe that soon she would be encouraging the youngster to get a move on since there would be another young one vying for her attention and resources. Young Bornean Orangutans often stay with their mother for several years, a necessary amount of time so that they can learn the ways of the forest from their mother. As Orangutans eat a wide variety of fruits from over 100 species of tree, it takes time to learn what to eat at certain times of the year.

Bornean Orangutan - Kinabatangan River, Sabah, Malaysia

Watching the Bornean Orangutans - Kinabatangan River, Sabah, Malaysia

During one of his lectures throughout the trip, Dr. Dominy explained some key differences with regards to the natural history of Sumatran and Bornean Orangutans, based on the geological origins of Sumatra and Borneo. These differences make Bornean Orangutans more susceptible to negative consequences as the result of global warming. I will attempt to accurately summarize what Dr. Dominy discussed with our group, below.

Sumatra is relatively young geologically, and is volcanic in origin, while Borneo is older and has been created by continental plate collisions with no currently active volcanoes. The soil in Sumatra is generally of good quality due to the relatively recent volcanic activity, whereas Borneo has very pool soils, exacerbated by excessive leaching caused by frequent rainfall. As a result, trees in Sumatra generally produce fruit throughout the year since nutrient levels are high, while in Borneo trees undergo masting events to conserve resources. Masting is the process whereby individuals of a plant species will produce large number of fruit/seeds synchronously, separated by a long period in which no or few fruits/seeds are produced. While there is no consensus as to what exactly triggers the masting events to occur, there is evidence that a colder than average preceding year will trigger the phenomenon.

Bornean Orangutans feed primarily on a wide variety of fruits, and as a result they have evolved over time to withstand these boom and bust cycles caused by masting. In mast years, the average body condition of Bornean Orangutans generally improves and reproduction is more frequent with the species, since food resources are abundant and easy to come by. In non-mast years, reproduction is more rare and body condition of individuals slowly deteriorates on average, since food is less abundant. There are still trees that produce fruit during these "dry spells", since not every tree species undergoes this masting strategy. Typically these mast years occur every 5-7 years if I recall correctly, which is frequent enough to ensure the survival of Bornean Orangutans. However, there is now evidence that global warming is reducing the frequency of these colder than average years, the years that likely trigger masting to occur. Instead of occurring every 5-7 years, mast years occur less often such as every 8 or 10 years. A difference of two or three years on average is just enough to tip the scales.

While a ton of money and effort has gone into rehabilitation of orphaned individuals, habitat protection and other direct efforts in an attempt to save Bornean Orangutans, it might not be enough. The species just cannot evolve quickly enough to counteract these changes in masting frequencies, directly caused by global warning. It is still relatively early to see the effects of this but perhaps in several decades the impacts will be more apparent. Bornean Orangutans face many pressures that could impact their long-term survival, many of them directly caused by humans. But it might be these indirect effects caused by global warming that are the final blow.

Bornean Orangutans - Kinabatangan River, Sabah, Malaysia

We continued after everyone was thoroughly satisfied with their views (and photos) of the Bornean Orangutans. The excitement did not end, however, as I spotted a Storm's Stork flying towards us and quickly managed to get everyone else on the bird. Incredibly, it flew right over us and circled the boat two or three times, before flyng away from us and disappearing over the forest. Storm's Stork is listed by the IUCN as Endangered, due to its very small, rapidly declining population. Formerly a widespread species in undisturbed riparian forest in southeast Asia, Storm's Storks now number fewer than 500 individuals in the wild, with most individuals found in Borneo and Sumatra, along with a tiny, remnant population or two in mainland Malaysia/Thailand. The species is extremely sensitive to forest fragmentation, caused by conversion to oil palm plantations, logging, and the construction of dams. The Kinabatangan Wildlife Sanctuary remains a stronghold for Storm's Stork, though this was the only individual we would see on the trip.

Storm's Stork - Kinabatangan River, Sabah, Malaysia

While cruising along the river we spotted this sleeping Asian Water Monitor on an overhanging branch.

Asian Water Monitor - Kinabatangan River, Sabah, Malaysia

Eventually we reached a point in the river where we needed to turn around, since the sun was rising higher and our stomachs were grumbling. Along the way we stopped briefly to chat with this prawn fishermen who was having a successful morning from the looks of it.

We also briefly cut through a narrow channel through the forest that led into an oxbow lake. The time of day was not ideal and we did not see much wildlife in the oxbow lake, but the journey through the narrow channel was quite peaceful, as the songs from Sooty-capped Babblers and Black-and-yellow Broadbills rang out from somewhere unseen in the dense foliage.

Tributary off of the Kinabatangan River, Sabah, Malaysia

We motored back to the lodge, observing some flyover Blue-throated Bee-eaters, Crested Serpent-Eagles and a Crested Goshawk along the way. We enjoyed a hearty breakfast consisting of eggs, toast, beans, mee goreng and fresh fruit, rested for a few minutes which gave me a chance to chat with Laura and send her a few photos, and then re-organized ourselves to leave for another boat trip. This time we were heading to the nearby village of Sukau where we would explore the village and learn a little about day-to-day life here.

We returned from our visit early in the afternoon - just in time for lunch. I paused to photograph this "Elephant Crossing" sign. Apparently a small group of Asian Elephants used to pass by this location daily, stopping to rip up the boardwalk. This occurred frequently enough that the lodge gave up trying to repair the boardwalk. While this group of elephants no longer travels along this route, the sign still remains.

By 3:30 PM we left for our late afternoon boat trip, though within minutes of starting the heavy rains began. We pushed forward for a bit, but given the worsening conditions we called it off, heading back to the lodge. While the rains poured we enjoyed a coffee break inside and chatted with some of the other guests of the lodge, and by 4:30 PM the storm had mostly passed so we loaded ourselves back into the boat.

Several Saltwater Crocodiles, Proboscis Monkeys and Silvered Langurs were observed, including a rare pale morph of the Silvered Langur with reddish fur. It can be distinguished from the Red Langur by its light colored face, while the Red Langur has a black face. The langurs were a bit distant and the lighting was awful for photography so I apologize in advance!

Saltwater Crocodile - Kinabatangan River, Sabah, Malaysia

Silvered Langur (pale morph) - Kinabatangan River, Sabah, Malaysia

Silvered Langur - Kinabatangan River, Sabah, Malaysia

While the sun began dropping lower in the sky, illuminated against the steel gray of the retreating storm cloud, we began heading upriver to a location where Asian Elephants had been seen the previous night.

cruising along the Kinabatangan River, Sabah, Malaysia

As we rounded a bend we noticed a group of elephants feeding on the tall grasses lining the riverbank. I almost couldn't believe what I was seeing since it was my first time observing wild elephants. The group included 14 individuals, including adult females and several youngsters.

Bornean Pygmy Elephant - Kinabatangan River, Sabah, Malaysia

Further up the river on the other bank were an additional 9 individuals, for a total of 23. We couldn't believe our luck, with elephants on both sides of the river!

Bornean Pygmy Elephants - Kinabatangan River, Sabah, Malaysia

The Asian Elephant is one of three extant elephant species, along with the African Bush Elephant and African Forest Elephant. Currently the Asian Elephant is divided into four subspecies, one for each of the Sri Lankan, Bornean, Sumatran, and mainland Asian populations. A definitive subspecific review is awaiting the results of genetic studies.

The individuals in Borneo, often referred to as the Bornean Pygmy Elephant, are the smallest of all the Asian Elephants. While they used to be more widespread across the island, today they are limited to a few protected areas including the Kinabatangan River, the Deramakot Forest Reserve, the Ulu Kalumpang Forest Reserve and the Tabin Wildlife Reserve. A 2010 study estimated between 1,184 and 3,652 Bornean Pygmy Elephants remained in the five main populations surveyed.

Bornean Pygmy Elephants - Kinabatangan River, Sabah, Malaysia

Bornean Pygmy Elephant - Kinabatangan River, Sabah, Malaysia

Eventually the elephants on one side of the river decided that they had finished feeding on the far banks, and one by one slipped into the river to cross over to the other side.

Bornean Pygmy Elephants - Kinabatangan River, Sabah, Malaysia

Bornean Pygmy Elephant - Kinabatangan River, Sabah, Malaysia

Young ones stayed close to the sides of their mothers, with their trunks sticking out of the water like snorkles while they completed the swim across the fast-flowing Kinabatangan River.

Bornean Pygmy Elephants - Kinabatangan River, Sabah, Malaysia

Bornean Pygmy Elephant - Kinabatangan River, Sabah, Malaysia

Eventually the last of the elephants clambored up the steep muddy bank and slipped into the forest. Thoroughly satisfied with the experience, we turned the boat around and began heading back to the lodge. Behind us a beautiful sunset lit up the sky, a fitting end to the day.

rainbow along the Kinabatangan River, Sabah, Malaysia

Our guides Robert (left) and Ben were pretty thrilled that the elephants had "cooperated" by returning to the same stretch of riverbank to feed two nights in a row. It was certainly a highlight of the trip for us and I am sure they were quite relieved!

Our guides Robert (left) and Ben - Kinabatangan River, Sabah, Malaysia

Our day was not yet over, however. After a tasty dinner we headed back out to the boats for a short night cruise along the banks of the Kinabatangan. The rains from earlier in the afternoon were long gone and the night was calm, lending itself to perfect boating conditions.

Since it was already relatively late and we had had a busy day up to that point, we only spent about an hour along the river. I was really hoping to spot a Reticulated Python but unfortunately it was not to be. We did see a variety of roosting birds, including this Blue-eared Kingfisher which tolerated our approach.

Blue-eared Kingfisher - Kinabatangan River, Sabah, Malaysia

I noticed this Yellow-bellied Prinia sleeping in the grasses lining the riverbank.

Yellow-bellied Prinia - Kinabatangan River, Sabah, Malaysia

About a minute after seeing the prinia, my flashlight beam lit up the vibrant colours of a sleeping Stork-billed Kingfisher.

Stork-billed Kingfisher - Kinabatangan River, Sabah, Malaysia

Saltwater Crocodiles are much easier to find at night, simply because their eyeshine caused by the reflection of a light source is quite obvious even at a considerable distance. We saw well over a dozen in our flashlight beams along the river.

Saltwater Crocodile - Kinabatangan River, Sabah, Malaysia

Ben spotted this sleeping Proboscis Monkey along the banks just before we returned to the lodge. He looked a little sleepy and so we left him alone after a brief look and photo.

Proboscis Monkey - Kinabatangan River, Sabah, Malaysia

And with that, a spectacular day along the Kinabatangan had come and gone. The following morning we would be departing the area, heading inland to the Danum Valley. I can't wait until my next visit to the Kinabangan - hopefully a Reticulated Python will cooperate on my next visit!

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October 16, 2017 - Day 2 at the Danum Valley