Lee Kong Chian Natural History Museum
Lee Kong Chian Natural History Museum

The Road to RIMBA (IV) – In the Field

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The Road to RIMBA (IV) – In the Field

This post is the last of a four-part series documenting the inaugural RIMBA-Sarawak project expedition.

View of Sungai Engkari from the landing point at Nanga Segerak Field Station. Photo credit: LKCNHM.

After an exhilarating journey on wheels and longboat, the LKCNHM team have reached the Nanga Segerak Field Station. This is where the actual work begins!

A break in the dense vegetation along the trail offered a glimpse of the surroundings – seemingly endless, misty green hills. Photo credit: LKCNHM.

Lanjak Entimau Wildlife Sanctuary, where the Nanga Segerak Field Station sits, is contiguous with Betung Kerihun National Park on the Kalimantan side of Borneo. Together, they add up to almost 10,000 km2 of protected primary tropical rainforest, roughly twice the size of Brunei.

Nozzle-headed termite (Hospitalitermes sp., Nasutitermitinae) trail on a mossy tree trunk. Video credit: LKCNHM.

This vast tract of rainforest is home to the iconic Bornean orangutans and hornbills, but also the less familiar denizens of the forest, namely the terrestrial invertebrates (animals that lack an internal skeleton). These include insects, spiders, and snails, to name a few, and they make up 99% of the animal diversity in the tropics.

Winkler funnels help to sample terrestrial arthropods found in the leaf litter of the forest floor. Photo credit: LKCNHM.

How do we know what exactly lives in a forest? A forest that stretches as far as the eye can see, and then some! Well, the same way we do for any other given area – we sample from the field to get a working estimate. The better the sampling design, and the more sampling sites we obtain, the closer we can get to an accurate figure. This expedition serves as one of the first attempts to document the insect diversity of Lanjak Entimau Wildlife Sanctuary to piece together this part of the biodiversity puzzle. A team from the Singapore Botanic Gardens had already made their first forays to document the floral diversity in 2016, with beautiful discoveries (see Gardenwise for details), and we were eager to do likewise.

A Malaise trap is set up to sample flying insects along natural flight paths in the forest. Photo credit: LKCNHM.

Having a representative sample of the insect diversity in these forests is not an easy task, given our modest party of five, a limited time in the field, and the relatively lightweight equipment we could bring upriver. Nevertheless, we designed a sampling regime that targeted as wide a range of forest habitats as possible – from the forest canopy to the leaf litter in the forest floor. This involved the setting up of various insect sampling devices to capture insects found in their natural habitats.

Sampling along the forest trail using yellow pan traps, an effective but labour-intensive method that occupied most of our morning hikes. Photo credit: LKCNHM.

Elevational profile of one of the trails out of the field station. Photo credit: LKCNHM.

The sampling regime was exhausting work given the rugged terrain of the hills surrounding the field station. Existing trails climb along steep ridges and we ascended uphill and back twice a day.

A working lunch out in the field means gathering at a natural clearing along the forest trail to get some leg rest and sustenance, typically in the form of fried rice or fried instant noodles. Photo credit: LKCNHM.

On days we planned to explore deeper into the woods, we packed our lunches and undertook a full day’s hike before heading back to the field station by dinner time.

As the sun sets, our mercury vapour lamp got put into action to survey the nocturnal insect diversity in flight. Photo credit: LKCNHM.

There was no rest for the weary come nightfall, however, as a significant number of insects are nocturnal by nature and we intended to survey these night creatures as well. We deployed our newly minted canopy light trap in the field proper, with very satisfactory results.

Wilson, our canopy light trap, performing dutifully up among the tree tops near the field station. Photo credit: LKCNHM.

Our efforts paid off when the mercury vapour lamp set up at the helipad hillock attracted swarms of flying insects. The impressive scale of insect life in the Sarawak tropical rainforests became truly evident in this visual feast of fluttering colours in all shapes and sizes.

Six-legged galore: the mercury vapour lamp on a good night was abuzz with an abundance of nocturnal insects. Photo credit: LKCNHM.

Mingshi sorting through specimens collected the previous day. Photo credit: LKCNHM.

Altogether, the samples we collected offered only a glimpse into the true diversity of insects present in these ancient forests. It will still take us the next few years to fully process the estimated 4,700 specimens we collected from the surrounding hills of Nanga Segerak.

An Old World Jerusalem cricket (Stenopelmatidae, Orthoptera), one of the largest insects in Southeast Asia. Photo credit: LKCNHM.

One of the initial finds we made is a giant among insects: a palm-sized Jerusalem/King cricket! Related to the giant wetas of New Zealand, this Old World Jerusalem cricket is one of only two species endemic to Southeast Asia. This species is a welcomed rediscovery, first discovered in Borneo in the early 1900s and not reported since then.

Specimens collected from the canopy light trap include (clockwise from top left): ant alate (Formicidae sp.), ant-mimicking beetle (Coleoptera sp.), mayfly (Ephemeroptera sp.), wasp (Ichneumonoidea sp.), fig wasps (Agaonidae sp.), and riffle beetle (Elmidae sp.). Photo credit: Bernetta Kwek.

There is no doubt that more discoveries await us! We look forward to sharing them in time to come and we extend our sincerest gratitude to our host and organiser – Sarawak Forestry Corporation, for providing the best ground coordination ever experienced by our team! We felt very fortunate to have such dedicated staff members along with us and were very well taken care of throughout the expedition.

A fond farewell to our friends at Nanga Segerak before departure. Till next time! Photo credit: LKCNHM.

As we continue our efforts in documenting the biodiversity of Southeast Asia, it is clear to us that the Sarawak tropical rainforests remain one of the least explored and richest frontiers of biological discoveries that deserves greater attention as well as protection.

At Sungei Begua (Rajang river basin), NUS researchers and accompanying local staff sample for freshwater fish against strong currents. Photo credit: LKCNHM.

This year, another team from the museum embarked on a second field expedition under the auspices of the same RIMBA-Sarawak project, exploring a different area within Lanjak Entimau Wildlife Sanctuary, with a different faunistic focus. At the time of writing this post, they have just successfully completed their field work, with their own fair share of stories to tell. Stay tuned for the next chapter of the RIMBA-Sarawak expedition project!