Hand and mouth use during food acquisition and food processing under the experimental condition
All macaques acquired peanut either with their hand or mouth. We recorded 861 instances of FA by 76 individuals distributed across urban (N=160), semi-urban (N=553) and rural (N=148) groups. The use of hand during FA was comparable between urban and semi-urban groups, both of which were higher than the rural group (FA by hand ; Urban(P=160/160) = Semi-urban(P=551/553) > Rural(PL=141/148); χ2=23.61, df=2, p<0.0001; Cohen’s d Moderate-Low=0.426) (Fig. 1).
Extraction of nut from the shell was largely accomplished by the use of mouth and hand(s) and did not vary across the experimental groups. As a result, we focused our attention to deskinning of the extracted nut. Although, the occurrence of skin removal varied across groups (see Dhananjaya et al., 2021), monkeys removed the skin of peanuts either by using their hands, by using the tongue against mouth palate or by nibbling with their teeth while supporting the peanut with either, a single hand or both hands. From the perspective of organ use, the primary agents of peeling were the hands, the mouth and both, hand and mouth (hand-mouth). A cumulative record of 763 instances of peanut extraction was recorded, of which 197 were from the urban group, 396 were from the semi-urban group and 170 were from the rural group. Peels of peanuts were removed by exclusively using hand(s), exclusively within the mouth or a combination of hand and mouth. Use of hands to remove peel of peanut was the most widespread in the urban group, followed by the semi-urban and the least in the rural group (FP by hand:High(PH=92/197) > Moderate(PM=5/395) > Low(PL=0/170), whereas use of mouth to deskin peanut followed the reverse order (FP by mouth:Urban(PH=31/197) < Semi-urban(PM=230/395) < Rural(PL=132/170); χ2=154.28, df=2, p<0.0001; Cohen’sd High-Moderate=0.471). However, use of hand and mouth for FP was comparable between the urban and semi-urban groups and was the least in the rural group (FP by hand-mouth:Urban(PH=74/197) = Semi-urban(PM=160/395) > Rural(PL=38/170); χ2=17.32, df=2, p<0.001; Cohen’s d High-Low=0.498, Cohen’s d Moderate-Low=0.497) (Fig. 1).