Koompassia excelsa(Local name Mangaris) growing near the entrance gate to Tabin Wildlife Reserve in Sabah. K. excelsa is the largest bean plant (Family Leguminosae/ Fabaceae) in the world, with one giant individual recorded growing to 88 m.
A second species of Koompassia, K. malaccensis (Local name Kempas or Impas) is also common in lowland forest throughout Borneo. K. malaccensis has been recorded up to 60 m tall.
In most of Borneo’s dipterocarp forest the canopy tops out at 40-50 m so both Koompasia species are emergents , i.e. they tower above a canopy of smaller dipterocarp trees. Due to their height and prominent smooth white trunks Mangaris and Kempas are easy to recognise.
Koompassia flower morphology indicates that the pendant strings of tiny white flowers are targeted for pollination by nectar bats although bees are involved as well. The papery seeds (beans with a single wing) are wind dispersed.
The reasons for the pale trunk and the emergent height are obvious. Both nectar bats and giant honey bees Apis dorsata fly long distances at night searching for nectar sources. By providing abundant food on a prominent white trunk above the canopy Koompasias will be easy to find by nocturnal nomadic pollinators.
For the same reason giant, nomadic honey bees, Apis dorsata often build their giant hives hanging from the branches of Koompassia trees as shown above on a Koompassia malaccensis tree growing next to the canopy walkway at Sepilok.The orange arrow points to the comb of an Apis dorsata colony hanging from a Koompassia malaccensis tree next to the canopy walkway at Sepilok, Sabah.Sun Bears are expert climbers and raid beehives wherever they can. However the trunks of Koompasias are too wide, too tall and too smooth for Sun Bears to climb.This Kempas Koompassia malaccensis growing next to the Temburong river in Brunei frequently hosts the beehives of Apis dorsata. Notice the improvised ladder nailed to the trunk by locals from Kampung Batang Duri so that they can steal the honey.A fruiting Koompassia malaccensis growing next to the Belalong Canopy Walkway at Temburong in Brunei.The beans of Koompassia malaccensis are thin flat single winged beans called samaras. These beans are a favoured food of the local Hose’s Langurs which specialize in eating unripe seeds and immature leaves.
Hoses Langur (adult male) next to the Belalong Canopy Walkway, Temburong, Brunei. Koompassias benefit from the presence of active bees hives on their branches because the presence of bees deters langurs from feeding on the seeds. This may be an additional reason that Koompassia tree morphology prevents Sun Bears from climbing the trunk and raiding the beehives.Note that the leaves of K. excelsa are much smaller than the leaves of K. malaccensis as one would expect of a taller tree more subject to wind resistance above the canopy.
Koompassia excelsa growing near the Ulu Ulu Resort next to the Temburong River. A surprising fact about emergent Koompasias is that they are rarely damaged by lightning even though lightning storms are common in Borneo and often kill forest trees. Is it possible that the smooth trunk of the Koompassia covered in a thin film of water acts as lighting rod during storms thus protecting the tree ?
