Gashaka Primate Project

Gashaka, Nigeria

Gashaka Primate Project

Gashaka, Nigeria
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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.

Pascual-Garrido A.,Gashaka Primate Project | Pascual-Garrido A.,Complutense University of Madrid | Buba U.,Taraba State University | Nodza G.,Gashaka Primate Project | Sommer V.,University College London
Folia Primatologica | Year: 2012

We investigated the acquisition of plant materials from which Nigerian chimpanzees manufacture wooden tools to harvest insects and honey from nests of army ants, honey bees and stingless bees. Slender trunks of juvenile trees and branches are most commonly used, and bendable vines rarely, probably reflecting the need to work with relatively sturdy tools to extract resources. While several tools are sometimes sourced from the same plant, there is also evidence for a depletion effect, as multiple tool sources at the same site are often spaced several metres apart. Identified tool sources belong to 27 species of at least 13 families. Honey-gathering implements are often chewed upon by chimpanzees. Interestingly, twigs of the most commonly used honey-gathering species possess antibacterial propensities and are favoured by Nigerians as chewing sticks. This suggests that extractive tools might possess associated medicinal or stimulatory properties. We do not know if chimpanzees actively select specific plant parts or species as we cannot compare observed with expected frequencies. Nevertheless, about three quarters of tools are picked from plants more than 6 m away from the extraction site, potentially indicating some degree of forward planning. Copyright © 2012 S. Karger AG, Basel.

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.

PubMed | Gashaka Primate Project and University College London
Type: | Journal: American journal of physical anthropology | Year: 2016

At some sites across Africa, chimpanzees consume army ants, often aided by plant tools, although consumption frequencies vary greatly. Other populations do not eat these insects at all, despite apparent abundance. The relative importance of this type of myrmecophagy for chimpanzee diet therefore remains unclear. We investigate if army ants constitute a preferred food or a fallback resource for chimpanzees at Gashaka, Nigeria, where army ants are consumed much more frequently than elsewhere.Long-term records on temporal variation of climate and availability of fruit as the chimpanzees preferred food are compared with rates of recovered army ant dipping wands and army ant remains in feces.Despite strict seasonality of rainfall and fruit abundance, myrmecophagy does not negatively correlate with fruit availability. Instead, army ant eating is sustained year round at high levels, with 44% of feces containing remains.Results contradict the fallback hypothesis and support the hypothesis that ants are a preferred food. Nevertheless, compared with fruit, ant-meals can normally provide only negligible amounts of nutrients. At Gashaka, however, nutritional yield may be significant, given that ant-dipping sessions provide on average 13 mg of dry weight to a chimpanzee. The species exclusively eaten here, Dorylus rubellus, might be particularly aggressive, thus resulting in greater harvesting success than elsewhere. Army ants may hence serve as a diet supplement or complement in terms of macro- or micronutrients.

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