Sommer V.,University College London |
Buba U.,Gashaka Primate Project |
Buba U.,Taraba State University |
Jesus G.,University College London |
And 2 more authors.
Ecotropica | Year: 2012
Various populations of chimpanzees attack beehives to obtain honey, often with the help of wooden tools. However, little is known about how honey abundance in tropical habitats fluctuates with season and how chimpanzees respond to this. For a woodland-savannah habitat inhabited by the Nigeria-Cameroon chimpanzee subspecies, we analyzed monthly proportions of flowering trees and vines as a proxy for honey production. We found a stria negative correlation between flowering and rainfall, probably because pollination benefits from dry conditions. Honey-gathering behavior of the Gashaka-Kwano chimpanzee community was reconstructed from tools abandoned at extraction sites. The apes use sturdy digging sticks and more slender probes, sometimes successively as a tool set, to access honey from subterranean and tree-dwelling colonies of stingless bees and honeybees. Chimpanzees exploited beehives throughout the year. However, during the dry season, when colonies had presumably hoarded more honey, hives were targeted with a greater number of tools. This was not because chimpanzee foraging party sizes had increased. Instead, individual apes used more probes during a given honey-gathering event - suggesting that dipping remained worthwhile for longer. In this situation, as tool tips become soft and unsuitable after prolonged dipping, the chimpanzees need to source new implements that possess hard tool points. The apes did not obtain them by breaking previously used tools into fragments, as these would be too short for successful insertions. We assume this because the average length of tools did not decrease with the increased number of apes that worked a hive. This indicates that each tool is sourced individually from raw material in the surroundings of the extraction site. Chimpanzees thus adjust the use and manufacture of tools to honey abundance, reflecting that the sugary fluid is a sought-after resource. © Society for Tropical Ecology. Source
Pascual-Garrido A.,Complutense University of Madrid |
Pascual-Garrido A.,University of Oxford |
Umaru B.,Gashaka Primate Project |
Umaru B.,Taraba State University |
And 4 more authors.
American Journal of Primatology | Year: 2013
Some chimpanzee populations prey upon army ants, usually with stick tools. However, how their prey's subterranean nesting and nomadic lifestyle influence the apes' harvesting success is still poorly understood. This is particularly true for chimpanzees (Pan troglodytes ellioti) at Gashaka/Nigeria, which consume army ants (Dorylus rubellus) with much higher frequency than at other sites. We assessed various harvesting and search options theoretically available to the apes. For this, we reconstructed annual consumption patterns from feces and compared the physical characteristics of exploited ant nests with those that were not targeted. Repeated exploitation of a discovered nest is viable only in the short term, as disturbed colonies soon moved to a new site. Moreover, monitoring previously occupied nest cavities is uneconomical, as ants hardly ever re-used them. Thus, the apes have to detect new nests regularly, although colony density is relatively low (1 colony/1.3ha). Surprisingly, visual search cues seem to be of limited importance because the probability of a nest being exploited was independent of its conspicuousness (presence of excavated soil piles, concealing leaf-litter or vegetation). However, chimpanzees preferentially targeted nests in forests or at the base of food trees, that is, where the apes spend relatively more time and/or where ant colony density is highest. Taken together, our findings suggest that, instead of employing a search strategy based on visual cues or spatial memory, chimpanzee predation on army ants contains a considerable opportunistic element. © 2013 Wiley Periodicals, Inc. Source