Wild chimpanzees using tools to raid bee nests have been observed in many parts of Africa. Now observations of chimpanzees in the Congo Basin indicate that they may have developed sophisticated technical solutions to gather honey that differ from those of apes in other regions.
Dave Morgan, of the Lester E. Fisher Center for the Study and Conservation of Apes, Lincoln Park Zoo, Chicago, and Crickette Sanz, of the department of primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany, monitored 40 episodes of tool use in honey-gathering by chimpanzees in the Goualougo Triangle, Republic of Congo, between 2002 and 2006.
“Pounding [hammering with a sturdy club] was the most common and successful strategy to open beehives,” they noted in their research paper. (Watch the video below.)
Video captures courtesy Morgan and Sanz
Chimpanzees at this site, in the southern portion of Congo’s Nouabalé-Ndoki National Park, used several tools in a single tool-using episode and could also use a single tool for many different purposes. “They exhibited flexibility in responses toward progress in opening a hive and hierarchical structuring of tool sequences,” Morgan and Sanz wrote.
The results supported suggestions of regional tool-using traditions in honey-gathering, which could be shaped by variation in bee ecology across the chimpanzee range, they added.
Bees have developed effective means of protecting their hives that most often involve the fortification and concealment of their nests. Different bee species show particular nesting habits, but there is also variation in nest building within species.
Some bees build nests in tree hollows or other preexisting cavities. Others may find lodging underground, in the forest canopy, or within the nests of other insects such as ants or termites.
Certain bees also restrict or close the nest entrance when an intruder is detected.
Another form of nest defense is to pursue or sting the intruder. Bees also have alarm pheromones that mark the raider so as to direct one another to the threat, the scientists said.
“The task of the honey-gathering chimpanzee is to overcome the defensive strategies of the bees themselves, breach the protective structure of the hive, and extract the honey and larvae.”
The different defense strategies of the bees could require honey raiders to apply different combinations of tactics.
Inserting a probe into a beehive to extract honey (dipping) is the most widespread tactic used by chimpanzees in honey-gathering. Chimps may also manually detach an entire hive or a branch segment that contains a bee nest, and then use a dipping tool to extract the honey. Using a tool as a lever to widen the access point to extract honey has been observed. Less commonly seen is use of a tool to dig or pry open subterranean hives.
Pounding of beehives seems exclusive to chimpanzee populations of the Congo Basin.
Morgan and Sanz observed 40 episodes of Goualougo chimpanzees using tools to gather honey, video-recording 30 of the episodes, representing 12 different individuals. “In total, we observed eight distinct types of tool actions during video recordings of honey-gathering. Beehive pounding was the most common tool tactic, accounting for 94 percent of all tool actions and shown by 11 individuals.”
To pound, or hammer, a hive, a chimpanzee uses the end of a stout branch to hit the entrance of a beehive to gain access to honey. “The function of this tool is to weaken or break the area near the entrance of the hive to provide a larger access point,” the researchers said in their paper. “The pounding action often causes the end of the club to become blunt and smooth.”
Chimps were observed pounding a hive as many as a thousand times in a single session.
“Chimpanzees were successful in obtaining honey in half (52%) of our video-recorded observations. It was clear that they expended significant effort to open the hive and attain relatively small amounts of honey,” the scientists noted.
Most honey-gathering episodes in Goualougo involved one or two tools, but up to five tools were used by a single individual during a successful honey-gathering episode. Chimps did not use multiple tools simultaneously, but one after another in a serial fashion.
“Pounding was the most successful technique to open a hive, but chimpanzees exhibited flexible strategies and insightful problem solving in honey-gathering,” Morgan and Sanz said. “We made repeated observations of sequential use of [more than] two types of tools, which is a behavior pattern that is rarely observed in other wild ape populations.”
The rich behavioral diversity and technological traditions of wild chimpanzees has important, but often overlooked conservation value, the scientists concluded. “Each wild chimpanzee population has a distinct repertoire of tool-using behaviors, and the preservation of these technological traditions should be another consideration for long-term conservation strategies.
Tool behaviors observed in honey-gathering by wild chimpanzees
(Adapted from the research paper by Dave Morgan and Crickette Sanz)
Map showing showing where different forms of tool use by chimpanzees were observed in Africa courtesy Morgan and Sanz.
Also known as honey pound or honey hammer. Chimpanzee uses end of a stout branch to hit the entrance of beehive to gain access to honey. The function of this tool is to weaken or break the area near the entrance of the hive to provide a larger access point.
Also called honey fish or collector. Chimpanzee inserts twig or stick into entrance of hive. The stick is extracted and honey is transferred to the mouth. The function of this tool is to collect honey from the hive. Some populations have been reported to use frayed dip sticks, but dip sticks may also become frayed as a byproduct of repeated dipping into the hive.
Chimpanzee holds one end of a twig or stick tool and pushes the other end either into the hive entrance or on the area near the hive entrance. This action may be repeated several times, and the chimpanzee may visually examine or smell the end of the tool between probing. Tool function seems to be determining the presence of bees, verifying access into the hive, or testing the structural integrity of the nest.
Also known as bodkin, pry, or enlarger. Chimpanzee inserts stick tool into hive entrance and then moves the tool vigorously within the nest. Insertion of the tool into the nest and pressing against the sides of the hive structure may provide leverage to widen access to the inner chambers of the hive or break the inner structures of the hive. The sides or ends of the tool may show wear from friction with the hive entrance or inner nest chambers.
Push with foot
Chimpanzee places end of tool at hive entrance, and a foot on the other end of the tool to apply force on the hive entrance. The function of this tool is to weaken or break the area near the entrance of the hive.
Chimpanzee hits side of stick or club against hive entrance. Sides of tool show wear. Rather than focusing specifically on the hive entrance, these forceful blows with the side of the club may serve to weaken the structure of the area around the hive as well as the hive entrance.
Press and hold
Chimpanzee holds midsection of tool and places end of tool at the hive entrance, and pushes for several seconds. In addition to possibly weakening the hive structure, pressing and holding for several seconds may also provide information about the structural integrity of the hive.
Chimpanzee places end of tool at hive entrance and then rotates tool as if drilling into the nest. Tool stays in contact with nest while rotated. The function of this tool is to provide a larger access point into the hive.
Also known as brush. Chimpanzee uses leaves or leafy twig to dispel insects that mob the hive attacker. The tool is vigorously whisked or swatted at insects near the entrance of the hive or around the body of the tool user.
Also known as perforator. Chimpanzee uses a stick tool to access a subterranean beehive. Tools are used to pry soil from entrance or dig into earth. The function of the tool may be to locate the exact location of the underground hive, provide an access point to the hive, or perforate the hive structure itself to access to honey.
“If present, adult bees block the entrance with their abdomens, ready to sting. The chimpanzee then disables them with the stick to make them fall out and eats them rapidly. Afterwards, the chimpanzee opens the branch with its teeth to obtain the grubs and the honey.” (Boesch, C., & Boesch, H. (1990). Tool use and tool making in wild chimpanzees. Folia Primatologica, 54, p. 89)
Long strips of bark are used to collect honey from a beehive.