www.sciencemag.org/cgi/content/full/340/6131/483/DC1

Supplementary Materials for

Potent Social Learning and Conformity Shape a Wild Primate’s Foraging Decisions

Erica van de Waal, Christèle Borgeaud, Andrew Whiten*

*Corresponding author. E-mail: aw2@st-andrews.ac.uk

Published 26 April 2013, Science 340, 483 (2013)

DOI: 10.1126/science.1232769

This PDF file includes:

Materials and Methods Supplementary Text Figs. S1 to S4 Tables S1 to S4 Captions for movies S1 and S2 Databases References (35–39)

Other Supplementary Material for this manuscript includes the following: (available at www.sciencemag.org/cgi/content/full/340/6131/483/DC1)

Movies S1 and S2

1

Supporting Online Material:

Materials and Methods

References for Methods (35-37)

Supplementary Text

References for Supplementary Text (38-39)

Supplementary Figures S1-S4

Supplementary Tables S1-S4

Movies S1-S2

Databases

Materials and Methods

Study populations and field site

The study was conducted between August 2011 and July 2012 as part of the Inkawu

Vervet Project in a 12,000-hectares private game reserve, “Mawana”, in KwaZulu Natal, South

Africa (S 28° 00.327; E 031° 12.348).

Based on Köppen-Geiger climate classifications (35), the region has a subtropical climate

characterized by warm wet summers from November to February and mild, moist to dry winters

from May to August. From March to April, the temperatures and the precipitations decrease

slowly during autumn and the opposite occurs during spring, from September to October. The

vegetation of the study site is classed as Savannah biome, characterized by areas of grasslands

with dispersed singular or clusters of trees forming a mosaic with the typical savannah thornveld,

bushveld and thicket patches (36). Mawana supports a substantial fauna including such species

as elephant, rhinoceros, hippopotamus, giraffe, zebra and numerous species of antelope. The

common predator complement includes hyena, jackal, caracal, serval and several species of

snake and eagle.

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Subjects were vervet monkeys, Chlorocebus aethiops, in four habituated groups. During

the study, monkeys lived in stable family groups which varied from 24 to 44 individuals. Groups

were typically composed of an alpha male, subordinate males and several matrilines (females

and their offspring). Female vervets remain in their natal group all their life, while males migrate

to other groups when they are sexually mature, usually around 4 years of age. Between January

and June 2012 we recorded 10 identified males migrating between the four study groups, and

five males immigrating from unknown origins (non-habituated, neighbouring groups) as shown

in Fig.S2. Some of these males stabilized their residence in their new groups whereas others

were just seen more fleetingly and participated in only one experimental trial in their new group.

Vervet infants are born during a synchronized period of about three months after the winter. We

recorded 27 births in 2011 between 16 September and 27 December. The four study groups –

Ankhase, Baie Dankie, Noha and Lemon Tree – lived in contiguous and overlapping home

ranges along a river. Home range sizes approximated 160 hectares (37). Group compositions are

summarized in table S1.

All individuals were identified by their faces. A recognition file with portrait photographs

and specific individual features (scars, color, etc) was constructed for each group. Monkeys were

named with letter codes. Matriline membership assignment was based on behavioral data:

mothers nursing infants and adult females frequently being close to and tolerant of juveniles in

feeding and resting contexts were taken as evidence for matriline membership (genetic sampling

is being conducted and will in future deliver more detailed relationship data for all the vervets in

these populations).

Training Phase

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In an initial training phase, each group was provisioned with a plastic box (34 x 14 x 12

cm) containing soaked corn in quantities (2.5 kg. approx.) such that even subordinates could

eventually access the food, typically after dominant individuals had finished eating (Figs S3, S4).

The box was fixed on the ground in a clearing offering observers a clear view, using rope and

tent pegs. We first conducted a training session, offering normal soaked corn, to habituate the

monkeys to eating corn out of this box. Once all were eating corn we added some colored corn

(either blue or pink) and increased the proportion of colored corn until the box contained only

colored corn and all monkeys were eating it. The two colors were chosen because they are

prominent in male vervets’ genitals and thus clearly perceptible and significant to these

monkeys. We then conducted three monthly ‘aloe-sessions’ with two adjacent, similar boxes

containing corn, one with the usual colored corn and one with the alternative color and a

repulsive, bitter taste due to soaking alongside aloe leaves (mountain aloe ‘Aloe marlothii’ was

collected in the field and the corn was soaked with the cut open leaves overnight). For two

groups the aloe-treated corn was the blue one (Lemon Tree and Noha groups), for two others, the

pink corn (Ankhase and Baie Dankie groups). The aloe training phase was stopped as soon as the

first infant tried eating some corn. This limited the training to three sessions only, by which time

very few adults were still trying the aloe-treated corn (Table S2). Both boxes were initially half

full (same total amount of corn as in earlier trials with one box only). If one of the boxes became

nearly empty it was refilled to the half way level, to ensure that monkeys would always have

access to both colors of corn and that the level of corn remained sufficient in each box to avoid

any bias due to food available.

Test Phase

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Once all infants were eating some solid and varied foods (after the first three months in

which they only nursed), the experimental testing phase was begun. This varied from four to six

months after the training phase. This variation was due to a longer period needed to identify all

infants in Lemon Tree group, as this group was less habituated than the others. The experiment

consisted of five test trials at intervals of 1, 1, 2 and 4 weeks, with two boxes containing the

same colored corn as in the earlier training phase, but now without any soaked in aloe, so that all

was palatable and edible (Table S3 A). Viewed from the camera and observers’ perspective, the

side of the pink and blue corn was alternated across test trials.

Data collection and analyses

All experiments were video recorded using a camcorder mounted on a tripod. The image

included the two boxes and approximately 1 meter on each side. In addition on each minute we

recorded who was eating at the boxes. A minimum of two observers conducted and recorded the

experiments. In the aloe training phase we recorded a total of 109 individuals that learned to

prefer one color and avoid the other (details in Table S2).

We applied a focal sampling method during the field experiments and where necessary in

supplementary video analysis to record each individual processing (eating, or spitting out) less

than, or more than, six corn grains of each color per session. Coding was unambiguous as it was

always conducted when individuals where facing the observers while eating and the color of the

corn was easily visible. Videos were additionally coded in detail for the first trial where naïve

group members (infants and immigrant males) ate for the first time, to code for order and the

duration of eating each color, identity of neighbors eating simultaneously, and what color

neighbors were eating.

5

All statistical analyses were performed using IBM SPSS 19.

References for Methods

35. M. Kottek, J. Grieser, C. Beck, B. Rudolf, F. Rubel, World Map of the Köppen-Geiger

climate classification updated. Meteorol. Z. 15, 259-263 (2006).

36. L. Mucina, M. Rutherford, The Vegetation of South Africa, Lesotho and Swaziland

(Strelitzia 19. South African National Biodiversity Institute, Pretoria, 2006)

37. S. Mercier, Food distribution and home range use in wild vervet monkeys (Cercopithecus

aethiops pygerythrus): basic data for the study of group foraging traditions (MSc thesis,

University of Neuchâtel, 2011)

Supplementary Text

(i) Supplementary Statistical Analyses

1. In the main text we note that “When each of the ten migrants first fed with no monkey higher

ranking than themselves present, their preference for the locally consumed color was even more

pronounced (choices 9/10 versus 0/11: Fisher Exact Test, p < 0.0001).” Additionally, we note

that migrants’ own earlier preferences after the training phase was almost identical, with the new

choices of 9/10 contrasting with 0/10 at the end of training (Fig. 3). Accordingly, the preferences

of all but Lekker among the migrants changed from their preferences before they migrated,

contrasting with the lack of change in any of the residents’ preferences.

2. In addition, for all the migrants who ate during their first trial without high ranking individuals

around (excluding Lekker as he was never out-ranked) the percentage of time feeding on blue

food continued to be much higher for males migrating into groups where the norm was blue

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(n=4, median 86%, interquartile range 73-94%) than pink (n=6, median 0.8%, interquartile range

0-4%) (Mann-Whitney U test, z = -2.590, p = 0.01). Males were thus consistent in their changed

preferences.

(ii) Concepts and Definitions of Conformity

The original studies of conformity in social psychology defined it primarily in terms of two

features; a disposition to copy the choices of a majority of others in a social group, and a

willingness to subjugate one’s own countervailing knowledge in matching the majority’s choice

(e.g. 28: references are to printed text). It is this original concept we follow in interpreting the

behavior of the migrant males we studied, because of clear evidence for the second criterion and

strong circumstantial evidence for the first (i.e. migrants adopted the food preference of a

majority of the group they entered, after observing these monkeys eating). However in relating

our findings to the wider literature, it is important to recognize that in the course of the recent

resurgence of interest in conformity in comparative and evolutionary psychology, variants on

what counts as conformity have emerged (32). Notably, some studies have relied primarily on

just one of the two criteria above. Thus some experiments have tested only whether a subject

tends to copy the majority choice among two options, when the subject has no prior knowledge

or preference (e.g. 31); conversely, some other experiments have tested whether a preference is

reversed by social learning, but in relation to only a single model and not the majority among a

sample of potential models (e.g. 29). In addition, evolutionary theorists modeling the effects of

conformity have highlighted a particular level of the phenomenon in which individuals show an

exaggerated tendency to follow the majority, with important effects on the stabilization of within

and between group cultural differences (23, 27). They refer to this as conformity, whereas

7

Claidière and Whiten (32) suggest it may be helpful to recognize the distinction by referring to

‘hyper-conformity’. Recent reviews survey the proliferating social psychological,

developmental, comparative and evolutionary literatures on conformity (32, 38-39).

Additional Reference for Supplementary Text

38. T. J. H. Morgan, K. N. Laland, The biological basis of conformity. Front. Neurosci. 6, 87

(Epub 2012 Jun 14, doi:10.3389/fnins.2012.00087) (2012).

39. D. B. M. Haun, E. J. C. Van Leeuwen, M. G. Edelson, Majority influence in children and

other animals. Dev. Cog. Neurosci. 3, 61-71(2013).

8

Supplementary Figures

Fig. S1.

Home ranges of the four study groups overlaid on satellite image of the area. The lines of the home range are the most outwards points of the group movement collected with a GPS logger fitted

on an adult female in each group. The color of the home range represents the color the group was trained to eat as

their local preference.

Fig. S2.

Male migrations. Six males migrated from groups preferring blue to those preferring pink; four did the reverse

and five males immigrated from unknown groups. The home ranges of the four study groups are outlined in the food

color the group was trained on. See Fig. S1 for habitat underlay.

9

Fig. S3.

Experimental set up illustrating preferential foraging.

Maize corn dyed either pink or blue was provided intermittently in two adjacent containers. Photograph shows

participants in Baie Dankie group all eating only ‘blue’, their local preference (c.f. Fig. 1 in main text).

Fig. S4.

Experimental set up illustrating that ranks affect priority of access to food.

Maize corn dyed either pink or blue was provided intermittently in two adjacent containers. Photograph shows the

dominant female and a juvenile monopolizing the local preference color, ‘blue’ and the second ranked female

waiting behind, displaying a scratching behavior often seen in conflict situations.

10

Supplementary tables

Table S1.

Group composition at start of experimental phase

Group AF AM JU IF totalBaie Dankie 12 3 19 9 43

Ankhase 6 2 (+5) 16 6 30Noha 11 2 (+5) 11 10 34

Lemon tree 7 4 (+5) 10 4 25total 36 11 (+15) 56 29 132 (+15)

Males (AM) were scored as adults once they migrated, while females (AF)

were scored as adults once they gave birth. Group members that did not fulfil

these criteria were scored as juveniles (JU), or as infants (IF) if born in 2011.

Numbers in brackets are the number of immigrant males during the whole

experimental phase.

Table S2.

Trained versus distasteful foods eaten during training phase sessions

group aloe trial Non-aloe > 6 aloe 1-6 aloe tot. aloe (avoiding ) avoid AK 1 22 5 6 11 (4) 5

2 26 4 7 11 (7) 10 3 20 0 6 6 (3) 3

total different ind. 26 5 8 13 (11) 13 BD 1 28 2 7 9 (3) 4

2 32 0 3 3 (2) 6 3 32 2 1 3 (2) 9

total different ind. 35 3 9 12 (7) 14 NH 1 24 13 5 18 (3) 3

2 20 0 4 4 (2) 4 3 10 0 0 0 0

total different ind. 24 13 5 18 (5) 5 LT 1 21 2 5 7 (2) 2 2 24 1 4 5 (4) 5 3 17 0 1 1 (1) 3

total different ind. 24 2 7 9 (6) 7 TOTAL 109 23 29 52 (29) 39

11

Responses of all participants during the three aloe training trials. Group: AK=Ankhase, BD=Baie Dankie,

LT=Lemon tree, NH=Noha. Non-aloe= total number of individuals participating in the trial and eating > 6 pieces of

corn of the non-aloe colour; > 6 aloe= number of participants that ate more than 6 pieces of aloe-treated corn; 1-6

aloe = number of participants that ate 1- 6 pieces of aloe corn; tot. aloe (avoiding) = total number of participants that

ate aloe corn, with in brackets the number of them that also avoided some aloe corn by either spitting it out or

peeling the outside of the corn; avoid= total number of participants avoiding aloe corn by either spitting it out or

peeling the outside of the corn.

Table S3 A.

Schedule of tests

1 week gap 1 week gap 2 weeks gap 4 weeks gap test trial 1 test trial 2 test trial 3 test trial 4 test trial 5

AK 23.04.2012 30.04.2012 08.05.2012 19.05.2012 14.06.2012 BD 24.04.2012 01.05.2012 07.05.2012 21.05.2012 19.06.2012 LT 04.06.2012 08.06.2012 12.06.2012 23.06.2012 10.07.2012 NH 25.04.2012 02.05.2012 09.05.2012 22.05.2012 20.06.2012

Dates of the five test trials. Group: AK=Ankhase, BD=Baie Dankie, LT=Lemon tree, NH=Noha

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Table S3 B. Test data – trained versus alternative foods eaten by all monkeys

group test norm never aloe > 6 aloe 1-6 aloe tot. aloe (avoiding ) AK 1 31 8 15 8 23 (1)

2 33 8 15 10 25 (1) 3 32 6 22 4 26 (1) 4 29 5 22 2 24 (1) 5 29 12 15 2 17 (0)

total diff individuals 35 9 22 4 26 BD 1 27 20 4 3 7 (3)

2 30 11 11 8 19 (1) 3 32 14 15 3 18 (0) 4 40 7 32 1 33 (1) 5 30 4 25 1 26 (1)

total diff individuals 40 7 32 1 33 NH 1 32 23 6 3 9 (1)

2 34 19 12 3 15 (0) 3 35 14 15 6 21 (0) 4 34 12 17 5 22 (2) 5 32 8 22 2 24 (0)

total diff individuals 37 12 22 3 25 LT 1 21 13 5 3 8 (0) 2 22 8 12 2 14 (0) 3 26 11 12 3 15 (0) 4 25 7 18 0 18 (0) 5 26 8 17 1 18 (0)

total diff individuals 27 9 18 0 18 TOTAL 139 37 94 8 102

Responses of all participants during test trials. Group: AK=Ankhase, BD=Baie Dankie, LT=Lemon Tree,

NH=Noha. Norm = number of individuals eating >6 pieces of corn of the previously non-aloe color; never aloe =

number of individuals eating only the local norm and never eating or avoiding the previously aloe-treated color; > 6

aloe = number of participants that ate more than 6 pieces of corn of the previously aloe-treated colour;1-6 aloe =

number of participants that ate 1- 6 pieces of corn of the previously aloe color; tot. aloe (avoiding) = total number of

participants that ate corn pieces of the previously aloe color, with in brackets the number of them that also avoided

some corn of the previously aloe color by either spitting it out or peeling the outside of the corn; avoid = total number of participants avoiding corn of the previously aloe color, by either spitting it out or peeling the outside of

the corn.

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Table S4 A. Test data – choices of high and lower ranked mothers

group dom/non-dom test norm never aloe > 6 aloe 1-6 aloe tot. aloe AK = 6 mothers 3 Gag-Ula-Ham/ 1 3 / 3 2 / 0 0 / 1 1 / 2 1 /3

3 Nko-Isi-Mam 2 3 / 3 2 / 0 0 / 2 1 / 1 1 / 3 3 3 / 2 2 / 0 1 / 3 0 / 0 1 / 3 4 3 / 3 3 / 0 0 / 3 0 / 0 0 / 3 5 3 / 3 3 / 1 0 / 2 0 / 0 0 / 2 total different ind. 3 / 3 1 (AF1) / 0 1 (AF3) / 3 1 / 0 2 / 3

BD = 8 mothers 3 Oul-Pri-Asi / 5 1 3 / 3 3 / 2 0 / 1 0 / 0 0 / 1

5 Num-Wie-Kai- 2 3 / 3 2 / 1 0 / 2 1 / 0 1 / 2 Ris-Vro 3 3 / 3 2 / 2 1 / 1 0 / 0 1 / 1 4 3 / 5 0 / 1 2 / 4 1 / 0 3 / 4 5 3 / 3 2 / 1 1 / 2 0 / 0 1 / 2 total different ind. 3 / 5 0 / 1 (AF13) 2 / 4 1 / 0 3 / 4

NH = 10 mothers 3 Gen-Upp-Xai / 1 3 / 7 3 / 6 0 / 0 0 / 1 0 / 1

7 Par-Zar-Bog- 2 3 / 7 3 / 3 0 / 4 0 / 0 0 / 4 Tro-Rom-Lau-Jak 3 3 / 7 3 / 3 0 / 3 0 / 1 0 / 4 4 3 / 6 3 / 1 0 / 4 0 / 1 0 / 5 5 3 / 6 1 / 1 2 / 5 0 / 0 2 / 5 total different ind. 3 / 7 1(AF1)/2(AF7-AF9) 2 / 5 0 / 0 2 / 5

LT = 3 mothers 1 Dia (AF3)/ 1 1 / 1 1 / 1 0 / 0 0 / 0 0 / 0

2 Cam-Vic 2 1 / 1 1 / 0 0 / 1 0 / 0 0 / 1 3 1 / 2 1 / 1 0 / 1 0 / 0 0 / 1 4 1 / 2 1 / 0 0 / 2 0 / 0 0 /2 5 1 / 2 1 / 0 0 / 2 0 / 0 0 /2 total different ind. 1 / 2 1 (AF3) / 0 0 / 2 0 / 0 0 /2

TOTAL 10 / 17 3 /3 5 / 14 2 / 0 7 / 14 Group: AK=Ankhase, BD=Baie Dankie, LT=Lemon Tree, NH=Noha. Dom/non-dom= number of top 3 ranking

mothers / number of lower ranked mothers, with three-letter codes of females names, in brackets their actual rank if

AF ranked 1-3 were not all mothers. Norm = number of individuals eating >6 pieces of corn of the previously non-

aloe color; never aloe = number of individuals eating only the local norm and never eating or avoiding the

previously aloe-treated color; > 6 aloe = number of participants that ate more than 6 pieces of corn of the previously

aloe-treated color; 1-6 aloe = number of participants that ate 1- 6 pieces of corn of the previously aloe color; tot. aloe

(avoiding) = total number of participants that ate corn pieces of the previously aloe color with in brackets the

number of them that also avoided corn of the previously aloe color by either spitting it out or peeling the outside of

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the corn; avoid = total number of participants avoiding corn of the previously aloe color, by either spitting it out or

peeling the outside of the corn.

Table S4 B.

Fifth and final test trial – choices of high and lower ranked mothers, with Fisher Exact test

mother Never aloe

Some aloe

Dom 7 3 Non Dom 3 11

Dom / non dom = total number of top 3 ranking mother in all 4 groups / number of lower ranked mothers in all four

groups, who either never ate the previously aloe-treated food, or ate some of it. Fisher test, n = 24, p = 0.035.

Movies

Movie S1.

Migrating male, Izulu, eats some of the non local norm when out-ranked. Gelosi, another

migrating male, is monopolizing the ‘pink’ corn (local norm in this group LT); Izulu quickly

grabs some ‘blue’ corn.

Movie S2.

Migrating male, Izulu, eats the local norm when not out-ranked. The higher ranked monkey,

Gelosi, leaves the corn; Izulu now has the choice and eats ‘pink’ corn.

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Databases

Total corn eaten (g) trial 1 2 3 4 5 color norm other norm other norm other norm other norm other group

AK 2710 820 2266 1115 2030 1158 2310 780 2796 707 BD 1782 110 1654 403 1446 496 2794 1664 1840 781 NH 2033 254 2104 371 3116 445 2944 618 3186 930 LT 1942 560 2122 573 2110 849 1652 1092 1901 985

Number of infants eating local norm or other color at 1st trial color

groups local norm other

AK 6 0 BD 7 1 NH 10 0 LT 3 0 total 26 1

Number of infants eating without their mother and keeping learned preference

eat without mother yes no N infants 23 4

Resident males

group ID 1st eaten BD Pi norm BD Ru norm BD Oo norm AK Sa norm AK Ys norm NH Du norm NH Mi norm LT Ha norm LT Ne norm LT Vo norm LT Ja norm

total 11 all norm

16

Migrating males

group 1st test ID origin

1st eaten

out-ranked

if not out-

ranked

total time eating norm color later when not out-

ranked (s)

total time eating other color later when not out-

ranked (s) AK 1 EL LT norm No 880 59 AK 1 Th LT norm No 180 0 AK 2 Ar LT other Yes norm 70 34 AK 3 Qu NH norm Yes 0 0 AK 3 Bo ? norm No 44 12 NH 1 Au ? other Yes norm 279 12 NH 2 Er BD norm No 83 0 NH 2 Le BD other No other - - NH 3 Gr BD norm No 320 61 NH 4 Ch ? norm Yes 0 0 LT 1 Mf AK norm No 0 0 LT 1 Ge AK other Yes norm 672 11 LT 2 Sh ? other Yes norm 101 0 LT 3 Am ? norm No 0 0 LT 3 Iz AK norm No 78 0

17

References and Notes 1. S. Kawamura, The process of sub-culture propagation among Japanese macaques. Primates 2,

43 (1959). doi:10.1007/BF01666110

2. R. A. Hinde, J. Fisher, Further observations on the opening of milk bottles by birds. Br. Birds 44, 393 (1951).

3. A. Whiten, The second inheritance system of chimpanzees and humans. Nature 437, 52 (2005). doi:10.1038/nature04023 Medline

4. T. Slagsvold, K. L. Wiebe, Social learning in birds and its role in shaping a foraging niche. Phil. Trans. R. Soc. B. 366, 969 (2011). doi:10.1098/rstb.2010.0343 Medline

5. A. Thornton, T. Clutton-Brock, Social learning and the development of individual and group behaviour in mammal societies. Phil. Trans. R. Soc. B. 366, 978 (2011). doi:10.1098/rstb.2010.0312 Medline

6. L. Rendell et al., Why copy others? Insights from the social learning strategies tournament. Science 328, 208 (2010). doi:10.1126/science.1184719 Medline

7. A. Whiten et al., Cultures in chimpanzees. Nature 399, 682 (1999). doi:10.1038/21415 Medline

8. L. Rendell, H. Whitehead, Culture in whales and dolphins. Behav. Brain Sci. 24, 309, discussion 324 (2001). doi:10.1017/S0140525X0100396X Medline

9. C. P. van Schaik et al., Orangutan cultures and the evolution of material culture. Science 299, 102 (2003). doi:10.1126/science.1078004 Medline

10. A. Whiten, A. Mesoudi, Review. Establishing an experimental science of culture: Animal social diffusion experiments. Phil. Trans. R. Soc. B. 363, 3477 (2008). doi:10.1098/rstb.2008.0134 Medline

11. A. Whiten et al., Transmission of multiple traditions within and between chimpanzee groups. Curr. Biol. 17, 1038 (2007). doi:10.1016/j.cub.2007.05.031 Medline

12. M. Battesti, C. Moreno, D. Joly, F. Mery, Spread of social information and dynamics of social transmission within Drosophila groups. Curr. Biol. 22, 309 (2012). doi:10.1016/j.cub.2011.12.050 Medline

13. K. N. Laland, N. Atton, M. M. Webster, From fish to fashion: Experimental and theoretical insights into the evolution of culture. Phil. Trans. R. Soc. B. 366, 958 (2011). doi:10.1098/rstb.2010.0328 Medline

14. A. Whiten, V. Horner, F. B. de Waal, Conformity to cultural norms of tool use in chimpanzees. Nature 437, 737 (2005). doi:10.1038/nature04047 Medline

15. A. Thornton, A. Malapert, Experimental evidence for social transmission of food acquisition techniques in wild meerkats. Anim. Behav. 78, 255 (2009). doi:10.1016/j.anbehav.2009.04.021

16. E. van de Waal, N. Renevey, C. M. Favre, R. Bshary, Selective attention to philopatric models causes directed social learning in wild vervet monkeys. Proc. Biol. Sci. 277, 2105 (2010). doi:10.1098/rspb.2009.2260 Medline

18

17. R. L. Kendal et al., Evidence for social learning in wild lemurs (Lemur catta). Learn. Behav. 38, 220 (2010). doi:10.3758/LB.38.3.220 Medline

18. A. V. Schnoell, C. Fichtel, Wild redfronted lemurs (Eulemur rufifrons) use social information to learn new foraging techniques. Anim. Cogn. 15, 505 (2012). doi:10.1007/s10071-012-0477-y Medline

19. R. L. Kendal, B. G. Galef, C. P. van Schaik, Social learning research outside the laboratory: How and why? Learn. Behav. 38, 187 (2010) (special issue). doi:10.3758/LB.38.3.187 Medline

20. M. Dindo, B. Thierry, A. Whiten, Social diffusion of novel foraging methods in brown capuchin monkeys (Cebus apella). Proc. Biol. Sci. 275, 187 (2008). doi:10.1098/rspb.2007.1318 Medline

21. L. M. Hopper, S. J. Schapiro, S. P. Lambeth, S. F. Brosnan, Chimpanzees’ socially maintained food preferences indicate both conservatism and conformity. Anim. Behav. 81, 1195 (2011). doi:10.1016/j.anbehav.2011.03.002

22. Materials and methods are available as supplementary materials in Science Online.

23. P. J. Richerson, R. Boyd, Not by Genes Alone (Univ. of Chicago Press, Chicago, 2005).

24. A. Whiten, R. A. Hinde, K. N. Laland, C. B. Stringer, Culture evolves. Philos. Trans. R. Soc. B. 366, 938 (2011). doi:10.1098/rstb.2010.0372 Medline

25. L. G. Dean, R. L. Kendal, S. J. Schapiro, B. Thierry, K. N. Laland, Identification of the social and cognitive processes underlying human cumulative culture. Science 335, 1114 (2012). doi:10.1126/science.1213969 Medline

26. M. Pagel, Evolution: Adapted to culture. Nature 482, 297 (2012). doi:10.1038/482297a Medline

27. J. Henrich, R. Boyd, The evolution of conformist transmission and the emergence of between-group differences. Evol. Hum. Behav. 19, 215 (1998). doi:10.1016/S1090-5138(98)00018-X

28. S. E. Asch, Studies of independence and conformity. 1. A minority of one against a unanimous majority. Psychol. Monogr. 70, 1 (1956). doi:10.1037/h0093718

29. B. G. Galef, E. E. Whiskin, ‘Conformity’ in Norway rats? Anim. Behav. 75, 2035 (2008). doi:10.1016/j.anbehav.2007.11.012

30. T. W. Pike, K. N. Laland, Conformist learning in nine-spined sticklebacks’ foraging decisions. Biol. Lett. 6, 466 (2010). doi:10.1098/rsbl.2009.1014 Medline

31. D. B. M. Haun, Y. Rekers, M. Tomasello, Majority-biased transmission in chimpanzees and human children, but not orangutans. Curr. Biol. 22, 727 (2012). doi:10.1016/j.cub.2012.03.006 Medline

32. N. Claidière, A. Whiten, Integrating the study of conformity and culture in humans and nonhuman animals. Psychol. Bull. 138, 126 (2012). doi:10.1037/a0025868 Medline

33. S. Perry, Conformism in the food processing techniques of white-faced capuchin monkeys (Cebus capucinus). Anim. Cogn. 12, 705 (2009). doi:10.1007/s10071-009-0230-3 Medline

19

34. C. P. van Schaik, Animal culture: Chimpanzee conformity? Curr. Biol. 22, R402 (2012). doi:10.1016/j.cub.2012.04.001 Medline

35. M. Kottek, J. Grieser, C. Beck, B. Rudolf, F. Rubel, World Map of the Köppen-Geiger climate classification updated. Meteorol. Z. 15, 259 (2006). doi:10.1127/0941-2948/2006/0130

36. L. Mucina, M. Rutherford, The Vegetation of South Africa, Lesotho and Swaziland (Strelitzia 19. South African National Biodiversity Institute, Pretoria, 2006).

37. S. Mercier, Food Distribution and Home Range Use in Wild Vervet Monkeys (Cercopithecus aethiops pygerythrus): Basic Data for the Study of Group Foraging Traditions, thesis, Univ. of Neuchâtel (2011).

38. T. J. H. Morgan, K. N. Laland, The biological basis of conformity. Front. Neurosci. 6, 87 (2012). doi:10.3389/fnins.2012.00087

39. D. B. M. Haun, E. J. C. van Leeuwen, M. G. Edelson, Majority influence in children and other animals. Dev. Cogn. Neurosci. 3, 61 (2013). doi:10.1016/j.dcn.2012.09.003 Medline