Sun bears live in the tropical and subtropical forests of Southeast Asia, ranging from northeastern India and southern China through mainland Indochina and down into the islands of Borneo and Sumatra. Their habitat revolves around one resource above all others: fruit-bearing trees. Research across multiple forest types has found that the density of fruiting trees is the single best predictor of where sun bears show up, more so than canopy height, elevation, or any other measured habitat feature. But the picture is more complicated than “dense rainforest only,” and recent fieldwork has challenged some long-held assumptions about just how picky these bears are about where they live.
The Forest Types Sun Bears Use
Sun bears are not confined to a single kind of forest. Field surveys in areas where multiple forest types sit side by side have detected sun bear signs in lowland dipterocarp forest, sub-montane and montane forest, and mixed evergreen forest. In one study area that included all three habitats, bear signs turned up on more than 60% of sampling transects across every forest type.1PLOS ONE. The Shared Preference Niche of Sympatric Asiatic Black Bears and Sun Bears in a Tropical Forest Mosaic The biggest differences showed up in montane forest, where fruit was most abundant and Asiatic black bears were detected at much higher rates, roughly six times more often than sun bears. In the lowland and mixed forests that made up about 85% of the study area, the two bear species used habitat at similar rates.
Across their broader range, sun bears occupy peat-swamp forests, mangrove fringes, and even degraded secondary growth. Their geographic distribution spans a huge swath of South and Southeast Asia, but the largest remaining populations are concentrated on Borneo, Sumatra, and in the protected forests of peninsular Malaysia, Thailand, and Myanmar. Island populations tend to be more isolated, which makes forest connectivity especially important for their long-term survival.
Why Fruiting Trees Matter More Than Anything Else
If you want to predict whether sun bears are using a patch of forest, count the fruiting trees. Of ten habitat attributes measured in a comparative study of bear habitat, fruiting tree density came out on top as the strongest predictor for sun bear occurrence.2PLOS ONE. The Shared Preference Niche of Sympatric Asiatic Black Bears and Sun Bears in a Tropical Forest Mosaic Sun bears are among the most frugivorous of all bear species, and fruit dominates their diet when it is available. During peak fruiting periods in Borneo, nearly 100% of their diet consisted of fruit, spanning an impressive 115 fruit species from 30 plant families.3Biological Journal of the Linnean Society. Frugivory in sun bears (Helarctos malayanus) is linked to El Niño-related fluctuations in fruiting phenology, East Kalimantan, Indonesia
Figs, particularly strangler figs in the genus Ficus, serve as a critical fallback food. When other fruit runs out between masting events, figs keep fruiting on a less synchronized schedule, providing a lifeline that ties sun bears to forests where these trees grow. This dependence on figs means that any habitat disturbance that removes or kills fig trees has an outsized effect on whether bears can persist in an area.
The Feast-and-Famine Cycle of Mast Fruiting
Southeast Asian dipterocarp forests do not produce fruit on a steady schedule. Instead, many tree species synchronize their fruiting in episodic “mast” events, sometimes years apart, often triggered by the droughts associated with El Niño climate cycles. A long-term study in East Kalimantan, Indonesian Borneo, documented two mast fruiting events that occurred four years apart, both tied to El Niño episodes.4Biological Journal of the Linnean Society. Frugivory in sun bears (Helarctos malayanus) is linked to El Niño-related fluctuations in fruiting phenology, East Kalimantan, Indonesia During mast periods, fruit was so abundant that it comprised almost the entirety of sun bear diets. Between masts, the bears switched to a predominantly insect-based diet, tearing into termite mounds, ant nests, and stingless bee colonies.
This dietary flexibility is what allows sun bears to inhabit forests with such wildly unpredictable food supplies. But it also means that the quality of their habitat depends on two separate resource bases: enough fruiting trees for boom times, and enough deadwood and insect colonies to sustain them during the lean years. A forest that provides only one of these is a much worse place to be a sun bear than one that provides both.
How Sun Bears Use Logged Forests
One of the more surprising findings in sun bear research is that selectively logged forests are not necessarily bad habitat. In some cases, they are actually used more heavily than pristine primary forest. A study comparing sun bear activity in 14-year-old previously logged forest and adjacent primary forest in Sabah, Malaysian Borneo, found about 1.8 times the density of bear-climbed trees in the logged area.5Ecosphere. Sun bears use 14‐year‐old previously logged forest more than primary forest in Sabah, Malaysia The explanation came down to food. Logged forests had more dead wood, which supports the termites and beetle larvae that sun bears rely on between fruiting events. Stingless bees were also more common in the logged areas. Canopy closure still mattered; bears gravitated toward sections with denser canopy cover, and some parts of the logged forest had regrown enough canopy to match primary forest conditions.
Modeling work looking at future scenarios in Sabah projected that conventional selective logging would only reduce sun bear distribution by about 4%, a modest impact.6Biodiversity and Conservation. Determinants of sun bear Helarctos malayanus habitat use in Sabah, Malaysian Borneo and its predicted distribution under future forest degradation and loss Outright forest loss from industrial tree plantation expansion was a different story, reducing predicted sun bear distribution by roughly 11% under a high-loss scenario. The distinction matters: a logged forest that keeps its basic structure and tree diversity can recover enough to support sun bears, while a forest converted to monoculture plantation cannot.
Not all logging is equal, though. A comparison between a sustainably managed production forest (Deramakot) and a more heavily degraded area (Tangkulap), both in Sabah, found that sun bear presence was higher in the well-managed forest.7Forest Ecology and Management. Sustainable forest management is vital for the persistence of sun bear Helarctos malayanus populations in Sabah, Malaysian Borneo The takeaway is that the quality of logging practices, reduced-impact techniques that maintain canopy structure, leave large trees standing, and protect key food trees, determines whether a production forest remains viable sun bear habitat.
Where Sun Bears Sleep
Sun bears are largely solitary and spend a good deal of their time in the canopy, but they need resting and sleeping spots both on the ground and up in trees. A radio-tracking study in the rainforest of Borneo documented 26 bedding sites and found that the majority were fallen hollow logs.8Biological Conservation. Home range, movement and activity patterns, and bedding sites of Malayan sun bears Helarctos malayanus in the Rainforest of Borneo Other sites included standing trees with cavities, spaces underneath fallen logs or large tree roots, and tree branches high above the ground. The variety of bedding sites reflects a need for large-diameter trees and substantial deadwood, both of which disappear when forests are heavily disturbed or converted.
This is one reason that forest management recommendations for sun bear habitat consistently emphasize keeping large cavity trees intact. Even in production forests, retaining a network of old, large trees provides not just fruit but also the physical shelter that bears require. Trees with cavities large enough to accommodate a sun bear are typically old-growth specimens that take decades to develop, making them irreplaceable on any practical timeline.
Surviving on the Edge of Oil Palm
As Southeast Asian forests have been carved up by agricultural expansion, sun bears have increasingly been squeezed into small forest fragments bordered by oil palm plantations. A study tracking bears in exactly this situation, small forest patches wedged between a river and oil palm in Borneo, found that the bears adjusted their behavior in several ways.9Biodiversity and Conservation. Survival strategies of a frugivore, the sun bear, in a forest-oil palm landscape They selected areas farther from human activity, including plantations, river boat traffic, and buildings. They also shifted to being almost entirely nocturnal, avoiding daytime activity that would put them in contact with people. Within the remaining forest, they selected large trees for feeding and resting.
Perhaps most interesting, the bears did occasionally venture into the adjacent plantations to feed on oil palm fruit. This opportunistic use of plantation crops shows a degree of behavioral flexibility, but it also puts bears into conflict with plantation workers and managers. Human-bear encounters in these edge zones are one of the main drivers of direct persecution, where bears are killed or captured as agricultural pests.
A broader regional analysis found something counterintuitive: across landscapes, sun bear detections were actually higher in forests near human settlements, not lower.10Integrative Conservation. Sun Bear Ecology and Conservation: Multiscale Habitat Associations in Southeast Asia The likely explanation is that many of the remaining large forest patches in Southeast Asia happen to be close to human populations. At the local scale within those landscapes, bears avoided oil palm plantations but showed no strong negative response to general forest degradation. These findings challenged the earlier view that sun bears are strict habitat specialists that cannot tolerate any human presence. The reality appears more nuanced: they need forest, but they can cope with a surprising amount of disturbance around its edges, as long as the forest core remains.
When Fire and Drought Destroy the Pantry
The El Niño cycle that triggers mast fruiting also brings drought, and in the worst years that drought leads to catastrophic forest fires. The 1997–1998 El Niño event, one of the strongest on record, caused widespread fires across Borneo and Sumatra that burned millions of hectares of forest.11Ursus. Human–sun bear conflicts in East Kalimantan, Indonesian Borneo For sun bears, the damage went beyond losing forest area. Surveys comparing burned and unburned forest found that the density of sun bear food trees dropped by roughly 80% in burned areas, from about 167 fruit trees per hectare to just 37.12Biodiversity and Conservation. Impacts of El Niño related drought and forest fires on sun bear fruit resources in lowland dipterocarp forest of East Borneo Hemi-epiphytic figs, the main fallback fruit that keeps bears fed between masting events, declined by 95%. The diversity of food tree species fell by 44%.
This kind of fire damage is essentially a double blow. First, the drought itself suppresses fruiting in surviving trees. Then the fire destroys the trees themselves, including the fig species that would normally carry bears through lean periods. Recovery takes decades because dipterocarp trees grow slowly, and the fig species that sun bears depend on need existing large trees to colonize as hemi-epiphytes. A burned forest does not just have fewer bears temporarily; it may be unable to support sun bears for a generation or more.
Climate projections suggest that El Niño events could become more frequent or more intense, which would shorten the recovery time between fire-prone droughts. For sun bears, this means the margin for error in forest management keeps shrinking. Forests that burn repeatedly never get the chance to rebuild their fruit tree populations.
How Deforestation Is Reshaping Their Range
Sun bear range has contracted significantly over the past several decades, driven primarily by deforestation for agriculture, particularly oil palm and pulpwood plantations. A study tracking sun bear occupancy in and around Kerinci Seblat National Park in Sumatra found an overall decline in distribution, from an estimated occupancy of about 0.68 to 0.44 over the study period, though the confidence intervals overlapped.13Animal Conservation. Quantifying changes in sun bear distribution and their forest habitat in Sumatra The decline was not uniform. One subpopulation living in the area with the highest deforestation rate, nearly 1% of forest lost per year, saw a steep decline of about 9.4% per year. Subpopulations in areas losing forest more slowly appeared less affected.
This pattern highlights a threshold effect. Sun bears can apparently tolerate moderate levels of forest loss and degradation in their surroundings, but once deforestation exceeds a certain rate, the population starts to collapse. The Kerinci Seblat study confirmed the national park itself as a stronghold for sun bears while warning that illegal logging around its borders was eroding the buffer habitat that connects the park to other forested areas.
Protected Areas and the Value of Good Forest Management
Across their range, sun bear habitat use is consistently higher in protected areas than in unprotected production or convertible forests. Surveys in Sumatra found that habitat use was highest inside Kerinci Seblat National Park and in a connected protected forest, with progressively lower use in production forests and the lowest use in forests zoned for conversion.14Diversity and Distributions. Managing sun bears in a changing tropical landscape Protection status alone does not guarantee good habitat, since illegal logging and encroachment affect many parks, but on average the correlation is clear.
Outside protected areas, the management regime determines how useful a forest is for sun bears. The comparison between Deramakot (sustainably managed with reduced-impact logging) and Tangkulap (heavily degraded) in Sabah showed that the well-managed production forest actually supported higher sun bear presence than the degraded protected area.15Forest Ecology and Management. Sustainable forest management is vital for the persistence of sun bear Helarctos malayanus populations in Sabah, Malaysian Borneo The practical message is that good logging practices, maintaining canopy cover, protecting large trees and fig trees, and controlling poaching, can turn production forests into functional sun bear habitat. The bedding-site research from Borneo reached the same practical conclusion, recommending that well-designed logging operations maintain large cavity trees and fig trees specifically to benefit sun bears.16Biological Conservation. Home range, movement and activity patterns, and bedding sites of Malayan sun bears Helarctos malayanus in the Rainforest of Borneo
Connectivity Between Forest Patches
Even where individual forest patches are large enough to support sun bears, isolation can undermine long-term viability. Sun bears need to move between forest areas to find food during lean periods, to find mates, and to maintain genetic diversity across populations. Habitat corridors, strips or stepping stones of forest connecting larger blocks, are a standard conservation tool for addressing this problem. But designing corridors for sun bears is not straightforward. Research on multispecies corridor planning in tropical mammal communities has found that corridors built for one species may be less efficient for another.17PubMed. Evaluating multispecies landscape connectivity in a threatened tropical mammal community A corridor optimized for tigers, for example, might not overlap well with the paths sun bears would use, since the two species respond to different habitat features and move at different scales.
For sun bears specifically, the features that make a corridor usable are the same ones that define good habitat: fruiting trees, canopy cover, and some deadwood for insect foraging. A narrow strip of young secondary forest without large trees may function as a corridor for some wildlife but be essentially useless for a sun bear that needs to feed and rest along the way. Conservation planners in Borneo and Sumatra are increasingly trying to maintain or restore forested connections between protected areas, recognizing that isolated parks, no matter how well managed, cannot sustain sun bear populations indefinitely if animals cannot move between them.
How Tolerant of Disturbance Are Sun Bears, Really
The emerging picture of sun bear habitat use has shifted over the past two decades. Earlier assessments described sun bears as primary-forest specialists sensitive to any form of degradation. More recent evidence paints a more flexible animal. Regional-scale camera-trap surveys found no strong negative response to forest degradation at local scales, and the bears tolerated human proximity better than expected.18Integrative Conservation. Sun Bear Ecology and Conservation: Multiscale Habitat Associations in Southeast Asia Logged forests sometimes supported higher bear activity than primary forest.19Ecosphere. Sun bears use 14‐year‐old previously logged forest more than primary forest in Sabah, Malaysia Bears in fragmented landscapes behaviorally adapted by becoming nocturnal and exploiting plantation crops.
None of this means sun bears are fine with rampant deforestation. The key distinction is between forest degradation and forest loss. A selectively logged forest that retains its basic structure, including large trees, canopy cover, and a diversity of fruiting species, can bounce back enough to serve as sun bear habitat within a couple of decades. A forest that is cleared entirely and replaced with oil palm or industrial timber plantation is gone as sun bear habitat, full stop. Modeling in Sabah predicted that selective logging would cause only a small reduction in sun bear distribution, while outright forest conversion caused nearly three times as much loss.20Biodiversity and Conservation. Determinants of sun bear Helarctos malayanus habitat use in Sabah, Malaysian Borneo and its predicted distribution under future forest degradation and loss The difference between a forest that has been thinned and a forest that has been erased is the difference between a habitat that still works and one that does not.
The Insect Side of the Menu
Because so much attention goes to fruit, it is easy to overlook the other half of the sun bear diet: insects. During the long intervals between mast fruiting events, termites, ants, beetle larvae, and stingless bee colonies become the primary food source. Field surveys found insect-feeding signs on about half of transects in lowland forests, with raided stingless bee nests and excavated termite mounds among the most common signs.21PLOS ONE. The Shared Preference Niche of Sympatric Asiatic Black Bears and Sun Bears in a Tropical Forest Mosaic Sun bears left more insect-feeding signs than Asiatic black bears in the same forests, suggesting they lean more heavily on this food source.
The availability of insect prey is directly tied to deadwood. Fallen logs, rotting stumps, and standing dead trees host termite and beetle communities that sun bears excavate with their long, curved claws. Logged forests often have more deadwood than primary forests, which is part of why logged areas can attract sun bears. The connection between deadwood and bear activity was explicitly documented in the Sabah study comparing logged and primary forest, where dead wood abundance helped explain higher bear use of the logged areas.22Ecosphere. Sun bears use 14‐year‐old previously logged forest more than primary forest in Sabah, Malaysia Forest management practices that remove deadwood or “clean up” logged areas after harvest may inadvertently strip out a food source that bears depend on for survival between fruiting seasons.