RT Journal Article
SR Electronic
T1 Food hardness and stone tool weight in wild primate nut-cracking
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 267542
DO 10.1101/267542
A1 Michael Haslam
YR 2018
UL http://biorxiv.org/content/early/2018/02/19/267542.abstract
AB This study presents data on average stone tool weights and the hardness of foods processed by the three known stone-tool-using primate species: Burmese long-tailed macaques (Macaca fascicularis aurea), bearded capuchins (Sapajus libidinosus) and Western chimpanzees (Pan troglodytes verus). Each of these primates uses stone hammers to crack open nuts in the wild, making them suitable for inter-species behavioural comparison. This work draws on published results to identify a distinct difference in the tool weight/food hardness curve between chimpanzees and the two monkey taxa, with the latter reaching an asymptote in mean tool weight of just over 1 kg regardless of increasing food hardness. In contrast, chimpanzees rapidly increase their tool weight in response to increasing hardness, selecting average masses over 5 kg to process the hardest nuts. Species overlap in their preference for tools of 0.8-1 kg for opening foods of hardness 2-3 kN, suggesting that this conjunction may represent a primate stone-tool-use optimum.