The second reason for sun bear to be an arboreal mammal is that they like to rest, nap, and sleep on treetop. Obviously, they can do this equally well on forest floor, just like this —>
However, there is a problem sleeping on forest floor. If you have visited the lowland rainforest of Borneo, you probably notice the numbers of blood sucking leeches presence on the forest floor. Even though you appeared to be walking alone in the forest, you are never alone because there are always many leeches latched on you! They either feasting on your blood or trying really hard to find a vulnerable spot to enjoy a bloody meal.
So being a warm-blooded large mammal live in the rainforest that always wet and rain, the sun bear is better to stay up high off the ground when they take a break from their daily routine foraging for food or traveling on the ground. There is no better way to illustrate how sun bear have done it by showing photos taken by Chandra Dewana Boer at Wehea forest, East Kalimantan, Indonesia Borneo.
Sun bears are also known to be prey upon by reticulated pythons (huge snake that can grow up to 10 m long! seriously, I am not kidding ) and tigers in Mainland Asia and in Sumatra. In order to escape from a surprise attack by these predators, sun bear make nest and sleep high on tree. Earlier I have posted a rare video of Batik the sun bear making a tree nest. Below is another video of her sleeping high, about 35 m above the ground on her tree nest she made and slowly climb down from the tree. If she did not wear a radio-collar, I would never have guessed and found her so high off the ground in the thick canopy of Bornean rainforest.