Tool-use to obtain honey by chimpanzees at Bulindi: new record from Uganda.

Honey-gathering from bee nests has been recorded at chimpanzee (Pan troglodytes) study sites across tropical Africa. Different populations employ different strategies, ranging from simple 'smash-and grab' raids to use of sophisticated tool-sets, i.e., two or more types of tool used sequentially in a single task. In this paper I present evidence of tool-use, and the probable use of a tool-set, for honey-gathering by unhabituated chimpanzees at Bulindi, a forest-farm mosaic south of the Budongo Forest in Uganda. Between June and December 2007, 44 stick tools were found in association with 16 holes dug in the ground, corresponding to the period when stingless bees (Meliponula sp.) appeared in chimpanzee dung. In 11 cases the confirmed target was a Meliponula ground nest. Two potential tool types were distinguished: digging sticks encrusted with soil, and more slender and/or flexible sticks largely devoid of soil that may have functioned to probe the bees' narrow entry tubes. Reports of chimpanzees using tools to dig for honey have been largely confined to Central Africa. Honey-digging has not previously been reported for Ugandan chimpanzees. Similarly, use of a tool-set to obtain honey has thus far been described for wild chimpanzee populations only in Central Africa. Evidence strongly suggests that Bulindi chimpanzees also use sticks in predation on carpenter bee (Xylocopa sp.) nests, perhaps as probes to locate honey or to disable adult bees. These preliminary findings from Bulindi add to our understanding of chimpanzee technological and cultural variation. However, unprotected forests at Bulindi and elsewhere in the region are currently severely threatened by commercial logging and clearance for farming. Populations with potentially unique behavioral and technological repertoires are being lost.