Final answer:
The largest tree-dwelling mammal from Sumatra and Borneo is the Orangutan, specifically the species Pongo pygmaeus in Borneo and Pongo abelii in Sumatra. Orangutans significantly contribute to the biodiversity of their rainforest habitats, which are currently threatened by human activities such as deforestation for oil palm plantations.
Step-by-step explanation:
The largest tree-dwelling mammal native to Sumatra and Borneo is the Orangutan. There are two species native to these islands: Pongo pygmaeus in Borneo and Pongo abelii in Sumatra, with a third species, Pongo tapanuliensis, also present in Sumatra. Orangutans are solitary and arboreal, predominantly eating fruits. In contrast, gorillas, another type of great ape, live in Central Africa and primarily consume foliage.
Orangutans are distinct within the Asian rainforests, contributing to the region's exceptional biodiversity. However, their habitats in Sumatra and Borneo are under threat due to rainforest removal for timber extraction and oil palm plantations, which also endangers many other species in these ecosystems. The International Union for Conservation of Nature (IUCN) lists the Bornean orangutan as endangered. It is vital to understand the importance of conservation to protect these unique animals and their habitats.