ESM 1. Chimpanzee data analyses
Insectivory tool use – presence within site
We calculated the opportunity to encounter army ants and termites (Macrotermes) for
chimpanzees at Seringbara by multiplying density of insects with chimpanzee encounter
probability (Table 1). Encounter probability was based on altitudinal overlap between
chimpanzees and insects and calculated by multiplying the proportion of chimpanzee
signs with the proportion of army ant trails and Macrotermes mounds recorded across
altitude categories [1], and summing values for each altitude category to obtain an
overall encounter likelihood value. We plotted encounter likelihood (density x
encounter probability) against presence of tool use. Tool use was present for army ants
(high encounter likelihood) and absent for Macrotermes (low encounter likelihood).
Results are presented in Fig. 1.A.
Table 1. Opportunities for insectivory tool use based on army ant and Macrotermes densities,
encounter probabilities and encounter likelihood (density x encounter probability)
Insect species
Density (per km)
Encounter probability
Encounter likelihood
Tool use
Army ants
0.08
0.16
0.013
Yes
Macrotermes
0.04
0.04
0.002
No
Nut cracking tool use – presence across sites
We calculated opportunities for chimpanzees to encounter nut trees by summing nut
tree densities for all nut tree species at a study site [1] in order to obtain an overall nut
tree density value for each site (trees/ha). We plotted nut tree densities against presence
of nut cracking across study sites. Tool use was present only at sites with relatively high
nut tree densities (>8 trees/ha). Results are presented in Fig. 1.B.
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Insectivory tool use and fruit availability – within site
We assessed the necessity for tool use in insectivory at Seringbara by plotting monthly
values for Fruit Availability Index (FAI) against % of feces with ants, a proxy for army
ant consumption (Koops et al. Under review, [1]). Army ant consumption was not
correlated with monthly availability of ripe fruit (Spearman rank correlation: rs=0.34,
N=31, P=0.06). Results are presented in Fig. 1.G.
Tool use and seasonality – across sites
We assessed the relationship between seasonality and the number of subsistence tool
use variants. Subsistence tool use variants per study site were obtained from published
material [2]. Numbers of dry months (<100 mm rainfall) were obtained from the
literature (Table 2). Number of tool use variants was not correlated with number of dry
months (Pearson correlation: r=-0.16, N=10, P=0.67). Results are presented in Fig. 1.H.
Table 2. Intensity of seasonality (number of dry months) and subsistence tool use variants for
10 chimpanzee study sites
Study site
Sub species
Dry months
Tool use variants
References
Assirik
P. t. verus
7
4
[3, 4]
Bossou
P. t. verus
4
13
[5, 6]
Taï
P. t. verus
3
11
[4, 7]
Goualougo
P. t. troglodytes
5
11
[8]
Lopé
P. t. troglodytes
3
4
[9]
Budongo
P. t. schweinfurthii
4
1
[10, 11]
Gombe
P. t. schweinfurthii
6
12
[4, 10]
Kanyawara
P. t. schweinfurthii
6
2
[4, 12]
Mahale-M
P. t. schweinfurthii
5
5
[13]
Mahale-K
P. t. schweinfurthii
5
6
[13]
2
REFERENCES
[1] Koops, K., McGrew, W.C. & Matsuzawa, T. 2013 Ecology of culture: do
environmental factors influence foraging tool use in wild chimpanzees (Pan
troglodytes verus)? Anim. Behav. 85, 175-185.
[2] Sanz, C. & Morgan, D. 2007 Chimpanzee tool technology in the Goualougo
Triangle, Republic of Congo. J. Hum. Evol. 52, 420-433.
[3] McGrew, W. & Baldwin, P.J. 1981 Chimpanzees in a hot, dry and open habitat: Mt.
Assirik, Senegal, West Africa. J. Hum. Evol. 10, 237-244.
[4] Hunt, K.D. & McGrew, W. 2002 Chimpanzees in the dry habitats of Assirik,
Senegal and Semliki Wildlife Reserve, Uganda. In Behavioural Diversity in
Chimpanzees and Bonobos (eds. C. Boesch, G. Hohmann & L.F. Marchant), pp.
35-51. Cambridge, Cambridge University Press.
[5] Yamakoshi, G. 1998 Dietary responses to fruit scarcity of wild chimpanzees at
Bossou, Guinea: possible implications for ecological importance of tool-use. Am.
J. Phys. Anthropol. 106, 283-295.
[6] Takemoto, H. 2004 Seasonal change in terrestriality of chimpanzees in relation to
microclimate in the tropical forest. Am. J. Phys. Anthropol. 124, 81-92.
[7] Boesch, C. & Boesch-Achermann, H. 2000 The chimpanzees of the Taï Forest:
behavioural ecology and evolution. Oxford, Oxford University Press.
[8] Furuichi, T., Sanz, C., Koops, K., Sakamaki, T., Ryu, H., Tokuyama, N. & Morgan,
D. In press Why do wild bonobos not use tools like chimpanzees do? Behaviour.
[9] Tutin, C.E.G., White, L.J.T. & Mackanga-Missandzou, A. 1996 Lightning strike
burns large forest tree in the Lope Reserve, Gabon. Global Ecology and
Biogeography Letters 5, 36-41.
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[10] Wallis, J. 2002 Seasonal aspects of reproduction and sexual behavior in two
chimpanzee populations: a comparison of Gombe (Tanzania) and Budongo
(Uganda). In Behavioural Diversity in Chimpanzees and Bonobos (eds. C.
Boesch, G. Hohmann & L.F. Marchant), pp. 181-191. Cambridge, Cambridge
University Press.
[11] Reynolds, V. 2005 The chimpanzees of the Budongo Forest: ecology, behavour
and conservation. Oxford, Oxford University Press.
[12] Watts, D.P. 2012 Long-Term research on chimpanzee behavioral ecology in Kibale
National Park, Uganda. In Long-Term Field Studies of Primates (eds. P.M.
Kappeler & D.P. Watts), pp. 313-338. Heidelberg, Dordrecht, London, New York,
Springer.
[13] Takasaki, H., Nishida, T., Uehara, S., Norikoshi, K., Kawanaka, K., Takahata, Y.,
Hiraiwa-Hasegawa, M., Hasegawa, T., Hayaki, H., Masui, K., et al. 1990
Summary of meteorlogical data at Mahale research camp, 1973-1988. In The
chimpanzees of the Mahale Mountains: sexual and life history strategies (ed. T.
Nishida), pp. 291-300. Tokyo, University of Tokyo Press.
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