The Java Tiger (Panthera tigris sondaica)

[GuateGojira]

There is no direct evidence that Sumatran tigers forced the orangutans to live in the trees, after all, Borneo orangutans are also arboreal and that island don't have tigers (not in modern times, at least).

However, we most see the hole context of the case, in time and space. Orangutans evolved in the mainland of Asia, were tigers thrived, and latter traveled to the Islands, together with the large cat. It is also interesting that all great apes are basically arboreal, but only Orangutans pass most of they life in trees and rarely go down.

In Africa, the only great cat capable to kill great apes in the jungle is the leopard, but even they most be beware of the large males of the species, specially in the case of the gorilla. This, and the absence of the lion in the forested areas of Central Africa, are possible answer to why the African large apes are more land living in comparison with the orangutan, which lived with a great cat (tiger) that specifically live in the woods.

Other important point is that Borneo orangutans are recorded to travel more in the floor of the jungle, while those of Sumatra barely do this, living mostly in the trees. This could suggest that tigers (living or absent) do have some influence in the Orangutan behavior.

Obviously, these are just assumptions, but based in the available facts. A deeper investigation of the orangutan behavior could shed more light in the issue.
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