Throughout the year, chimpanzee food is quite varied, but it is mainly vegetable material. At times, however, the Gombe Park is loaded with insects-termites, ants, caterpillars- and the chimpanzees will eat huge numbers of them. The chimpanzees’ really remarkable behavior appears when they gather termites. According to Suzuki and van Lawick-Goodall, when chimpanzees see that termites have pushed open their tunnels on the surface, they will go off to find a suitable termiting tool. A foot-long, rather thin, straight twig is best, and it may take quite a while to choose suitable sticks; then extraneous side branches and leaves must be carefully cleared off. The ape may even select and prepare several at a time, carrying them all back to the termiting hill firmly cupped in the closed palm of the hand while it knuckle-walks. The chimpanzee will lie down on its side next to the termite hill, and with skill and care, stick the twig into one of the open tunnels. The stick is wiggled, then slowly withdrawn; if it has termites adhering to it, the chimp licks them off the tool, and does it again. The job may look simple, but it takes skill to maneuver the stick through the twisting termite corridors. This is complex learned behavior, involving the manufacture of an implement.
The word “them” refer to?
leaves
cleared-off sticks
branches with leaves
vegetable