These forest-dwelling elephants are smaller and darker than their savanna relatives and have smaller and characteristically rounded ears. The upper lip and nose are elongated into a trunk that is more hairy than that of the savanna elephants'. The trunk serves multiple functions, from acting as a dextrous 5th limb to a sound producer and amplifier, and an important method of touch between individuals. The trunk of the African species ends in two opposing processes (or lips), which differs from that of the Asian elephant (Elephas maximus), whose trunk ends in a single process. The other characteristic elephant feature, the modified upper incisors known as tusks, are generally almost straight and downwardly pointing in the forest elephant, rather than curving forward as they are in the savanna species. They are also a more yellow or brownish colour; these strong tusks are used to push through the dense undergrowth of their habitat. Bull elephants (mature males) are sometimes known to have exceptionally long tusks that reach almost to the ground.