Which mammal has a false thumb to grip bamboo?

The mammal with a false thumb for gripping bamboo is the giant panda. Its so-called thumb is an enlarged wrist bone that works alongside the five true fingers on each forepaw.

This structure is a modified radial sesamoid, a small bone associated with the wrist rather than a true opposable thumb. The panda uses it like a gripping digit, helping it hold, rotate, and strip bamboo stems and leaves. A panda may spend around 10 to 16 hours a day feeding because bamboo is relatively low in nutrients.

The false thumb is an evolutionary compromise. Pandas descended from carnivorous bear ancestors, whose forepaws were not designed for grasping plants. Their wrist adaptation improved bamboo handling without completely sacrificing the ability to walk on all four limbs. Fossil evidence suggests that panda relatives had similar structures millions of years ago.

The red panda is a common mix-up because it also has a bamboo-gripping false thumb. However, red pandas are not bears and belong to their own family, Ailuridae. In this question, the canonical answer is the giant panda.