Sun bears use 14‐year‐old previously logged forest more than primary forest in Sabah, Malaysia

Abstract

Sun bears (Helarctos malayanus), arguably the least-known bear species, are endemic to Southeast Asia and are believed to be in rapid decline due to forest loss and poaching, which are severe threats across this region. It has been asserted that, unlike other forest-dependent, omnivorous bears, sun bears are especially sensitive to changes in forest composition and canopy closure because they often feed on fruits in the canopy. We investigated habitat use of sun bears in a region of Sabah, Malaysian Borneo, containing primary forest adjacent to a 14-yr-old selectively logged forest. We used strip transects to quantify trees that sun bears climbed to forage or rest; these were easily recognized by distinctive claw marks. We found 1.8× the density of bear-climbed trees in the logged vs. the primary forest. Dead wood, a home for various insects eaten by sun bears, was more common in logged forests. Except during masting years, when fruits are exceptionally abundant in this area, sun bears commonly consume termites and bees, both of which were more common in the logged forest and had a positive effect on sun bear presence. Sun bear presence was also positively associated with canopy closure, which on average was higher in primary forest, but some portions of logged forest had very high canopy cover. The logged forest had higher vegetative greenness, which up to a point was attractive to bears, but very high greenness, likely indicative of thick underbrush, appeared to be less attractive. These results indicate that previously logged areas can be valuable habitats for sun bears, providing rich supplies of food--both fruits and insects. A number of recent biodiversity surveys using camera traps have also shown high use of logged areas by sun bears, but here we connected this use to food resources. Conservation of this species is better served by appreciating its omnivorous diet and adaptiveness to varying habitats and thus recognizing the importance of preventing logged areas from deteriorating into agriculture. We warn against focusing only on saving primary forests, and predicting declines of this species from forest cutting, without considering forest regeneration.

Understanding Species–Habitat Associations: A Case Study with the World’s Bears

“…Even photos can be misidentified as to the species, since some bears look alike [65,66]. Some kinds of bear signs can be confused with that of other species, so to avoid misidentification it may be preferable to only rely on types of signs that are definitive (e.g., claw marks on trees; [67]). However, this can lead to a bias if the more reliably identified sign occurs in certain types of habitats (Figure 3).…”

“…An alternate explanation for high rates of photo-capture under a dense canopy could be that bears tended to rest in shady areas to avoid heat stress [94]. Whereas other studies have confirmed that sun bears select for areas with high tree cover, a large number of studies have now demonstrated that sun bears are also widespread in degraded and successional forests in both the mainland and Borneo and Sumatra [67,[95][96][97][98][99]. Hwang et al also pointed to many other camera-trap studies that were not specifically directed at sun bears that have consistently shown high occupancy in forests 6-20 years after logging, and growing evidence that poaching is driving sun bear density more than habitat degradation [67,100].…”

“…This species' reliance on insects is often underappreciated. For example, Hwang et al found that sun bears used a previously logged forest more than an adjacent primary forest during a poor fruiting year because the logged forest, with more deadwood, provided a greater abundance of termites and bees [67]. Likewise, at a site in Thailand where sun bears and Asiatic black bears occur sympatrically, Steinmetz et al found that sun bears may be excluded from a habitat that provides high fruit abundance but can coexist with the larger black bears by concentrating on insects [26].…”

“…However, in years when red elderberry (Sambucus racemosa) fruited unusually early due to higher than normal spring temperatures, then coinciding with the main salmon run, bears unexpectedly departed the salmon streams to feed on these berries in the hillsides [232]. Likewise, sun bears, which clearly benefit from a bounty of diverse fruits during masting events in primary forests, nevertheless selected for a neighboring secondary forest that produced more insects when fruits were less available [67]. The same seems true for shelter: whereas sun bears often choose resting sites in the canopy of tall trees in primary forests, they use other types of trees to rest in secondary forests [97], and there is no evidence that their health or survival is reduced by doing so.…”

“…The profusion of available data in the hands of investigators who have limited experience with the species has the danger of creating what Nielsen et al [245] called a "technology trap", leading to misinterpretations and misguidance for practitioners. Studies on the ground are still needed to either verify or correct the deductions stemming from models [67].…”