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).