Tool-use for catching ants by chimpanzees at Bossou and Monts Nimba,West Africa

The use of tools by wild chimpanzees to catch ants was studied at Bossou and Monts Nimba, south-eastern Guinée. Insect-eating by chimpanzees at Bossou appears to be opportunistic and ant-catching was seen only in certain years. The most common prey species wasDorylus (Dorylus) molestus Gerstaecker. Sixty wands for catching ants were found at Bossou. Half of them were made from Zingiberaceae or Marantaceae, the stems and long petioles of which are usually straight, and have few branches. The length of the wand was variable. The mean length of ant-catching wands (46.7 cm) was between those found at Gombe and Tai. Ants' nests were usually dug up by hand, but on one occasion a digging stick was used. Four chimpanzees who used only one hand to manipulate the wand had also been observed using a stone hammer for nut-cracking. All of them used the same hand in wand-manipulation as in nut-cracking. As reported for chimpanzees at Gombe, Mahale, and Tai, more females than males tended to catch ants with wands though the sex difference was not demonstrated statistically. Ants which climbed up the wand were directly squeezed off using the lower-lip and eaten. This is the same method as seen at Tai, but different from most episodes observed at Gombe. Juveniles and infants also caught ants using wands, however, they seemed to do this more out of curiosity than as a means of feeding. At Goera, over 15 km from Bossou and separated from it by Monts Nimba, the same characteristics of ant-catching techniques were evident from traces.