Food Acceptance and Social Learning Opportunities in Semi‐Free Eastern Chimpanzees (Pan troglodytes schweinfurthii)

Abstract

When confronted with novel foods, chimpanzees' responses combine a mixture of curiosity and cautiousness. Once the item is in the mouth, the initial cautiousness is followed by an aversion to bitter taste that is mediated mainly by the TAS2R gene family. For instance, variations on the TAS2R38 locus which has been studied extensively in humans have been associated with different acceptance of bitter substances. Surprisingly, while cautiousness and bitter taste aversion were selected to prevent any risk of poisoning, very few studies on novel food acceptance have included the vegetative parts of plants. Moreover, the studies were usually carried out with captive apes faced to a very restricted variety of non-toxic plants, hardly making the results representative. This study aims to replicate previous findings obtained in zoos while controlling for these limitations. We provided nine subgroups of eastern chimpanzees (Pan troglodytes schweinfurthii) living in the Ugandan sanctuary of Ngamba Island with novel plants known to be consumed by wild chimpanzees of the same subspecies, as well as domestic plants, wild sapota fruit and grey clay used by human local communities. We also genotyped their TAS2R38 gene. Our results confirm the very low genetic heterogeneity for TAS2R38 in this chimpanzee subspecies. Chimpanzees were particularly cautious towards the vegetative parts of novel plants, likely reflecting their behavioural strategy for avoiding toxic compounds. We also confirmed their higher propensity towards testing sapota and clay, reflecting their ability to expand their diet. In contrast with the results found in zoos, familiar and novel less-palatable vegetative parts of plants did not elicit many interindividual observations. This may be explained by the items presented, which could have been so novel to be considered as enrichment in captive conditions, where the apes are rarely exposed to plants.

A review of research in primate sanctuaries

“…Among the first sanctuaries to embrace collaborations with external researchers interested in primate cognition was Ngamba. Researchers from several European and American universities have travelled there to work alongside sanctuary staff and resident chimpanzees on a wide range of topics; including, social learning in ecological contexts [127,128], problem-solving of a trap-tube task [129], deception [130], quantitative abilities [131], reasoning and inference abilities [132][133][134], perspective taking [135], inhibitory control compared across the great apes and human children [136], imitation and emulation [137,138], and one study finding that dogs (Canis familiaris) but not chimpanzees comprehend imperative human pointing [139]. Work at other chimpanzee sanctuaries in Africa followed suit, emphasizing individual [140] and social learning [141] in addition to comparative cognition research involving multiple species [142][143][144].…”

The curious case of great ape curiosity and how it is shaped by sociality

“…Here, we refer to this idea as the social curiosity hypothesis . Findings from captivity show social facilitation effects on chimpanzee's reactions to new food (Forss et al, 2019; Gustafsson et al, 2016) and suggest that more socially tolerant chimpanzee groups are also better at producing new innovations (Harrison et al, 2021). Thus, if relying on social information is a pathway for apes to reduce the risks involved in being curious, we expect the levels of intrinsic curiosity to be higher in less social species, where individuals more frequently must rely on their own motivation to search new information, compared to highly social species were the predisposition to attend to social cue should be stronger.…”

L’interspécificité du pharmakôn dans le parc Kibale (Ouganda) : savoirs partagés entre humains et chimpanzés ?

“…Il est cependant impossible d'identifier le premier contact d'un chimpanzé sauvage avec une espèce végétale et nous n'avons jamais observé de chimpanzé sauvage recrachant une plante inhabituelle, comportement qui aurait pu traduire un essaierreur. Nos travaux menés en parc zoologique ou en sanctuaire ont donc apporté des informations complémentaires et ainsi révélé que des chimpanzés face à des plantes non familières de la pharmacopée française ou ougandaise sont initialement néophobes, explorant visuellement, tactilement et olfactivement la plante inconnue(Gustafsson et al 2014(Gustafsson et al , 2016. Mais dès lors qu'un individu ose gouter la plante nouvelle, la curiosité et la grande socialité des chimpanzés ont pour conséquence une observation très proche par le congénères qui approche le plus souvent leur nez de façon très proche voire au contact de la bouche du consommateur.…”