Chimpanzee Nest Construction in Southwest Cameroon Cadell N. Last1, Bernice F. Muh2, Edwin N. Alongamoh2

1Dept. of Anthropology, McMaster University 2The Environment and Rural Development Foundation (ERuDeF)

Research Question •  Why do chimpanzees (Pan troglodytes vellerosus) construct terrestrial nests in one forest block (Andu) within the Lebialem-Mone Forest Landscape (LMFL) but not in another (Bechati)?

•  Hypothesis: Nest locations (terrestrial versus arboreal) vary in relation to the density of human occupancy, frequency of hunting, and cultural perceptions of primates in the region.

Literature on Chimpanzee Nest Construction •  Primatologists have been aware of terrestrial chimpanzee nest construction since the early 1990s (e.g., Fruth and Hohmann, 1993, 1994; Boesch, 1995; Reynolds and Reynolds, 1997) •  Terrestrial nests always appear to be constructed at a lower frequency than arboreal nests (Figure 1) •  Terrestrial nests are used as both day and night nests; they are usually less complex than arboreal nests •  Chimpanzees in West, Central, and East Africa have all constructed terrestrial nests •  Explanations for terrestrial nest construction : Altitude, seasonality, high winds, lack of available nesting trees, protection from cold ground, non-human predation, human predation, human development, socio-cultural factors (Hirata, 1998; Humle and Matsuzawa, 2001; Koops, et al., 2007; Pruetz, et al., 2008)

Figure 1.1 Terrrestrial chimpanzee nest Figure 1.2 Arboreal chimpanzee nest (Andu, LMFL, Southwest Cameroon) (Bechati, LMFL, Southwest Cameroon)

The Sites •  Research was conducted within two of the six forest blocks (Andu and Bechati) of the Lebialem-Mone Forest Landscape (LMFL) in Southwest Cameroon (Figure 2) •  LMFL covers 200,000 ha of forest and has altitudes as low as 200m and as high as 2700m above sea level •  The region experiences two severely different climatic seasons: the ‘rainy season’ (April - September) and the ‘dry season’ (October – March) •  Socio-economic activities engaged in by habitants of the LMFL include farming, fishing, logging, and collection of non-timber products (http://www.erudefconservation.org/Socio-%20economics.html) •  Bechati – 5,000 human inhabitants •  Andu – 20,000 human inhabitants •  Bechati and Andu forest blocks are both home to chimpanzees (Pan troglodytes vellerosus)

Methodology •  Research was conducted in Southwest Cameroon between July 16 – August 2, 2010 •  The primate field survey in Andu and Bechati collected chimpanzee (Pan troglodytes vellerosus) and gorilla (Gorilla gorilla diehli) related data (i.e., nests, food, tools, tracks, human manufactured primate traps, and shell casings, etc...) using a recce-transect field method •  Total observation and tracking hours: approximately 80 hours per forest block

Terrestrial Nest

Arboreal Nest

Terrestrial %

Bechati 0 20 0

Andu 11 34 24

Total            11 54 17

Table 1 – Data from both forest blocks demonstrating that terrestrial nests were only found in Andu, and represent one-quarter of all nests observed. No terrestrial nests were observed in Bechati.

Chimpanzees (Pan troglodytes vellerosus) of Cameroon

Discussion Hypotheses considered: •  Seasonality : cannot explain terrestrial nests at Andu because research has shown chimpanzees construct lower nests on average during the dry season (Fruth and Hohmann, 1994). This also does not explain why there are no terrestrial nests at Bechati •  Altitude: cannot explain terrestrial nests at Andu because terrestrial nests were not located at high altitudes where high winds and lack of appropriate arboreal nesting opportunities may cause terrestrial nest construction. Terrestrial nests were found at lower altitudes surrounded by many suitable trees for arboreal nesting

Proposed explanation: •  Human predation and development are key factors in terrestrial nest construction in Southwest Cameroon •  Chimpanzees at Bechati did not engage in terrestrial nest construction, whereas 24% of chimpanzee nests at Andu were terrestrial •  The only significant difference between the two sites is the frequency of human hunting, the density of human inhabitants, and the cultural perceptions of primates •  Bechati: organization of villages creates dense overlap with chimpanzee habitats, illegal bush meat trade still endemic, farmers view chimpanzees as a threat to agricultural development due to crop-raiding •  Andu: villages and chimpanzee populations separated, chimpanzees not hunted, agricultural expansion possible without destroying primate habitat or fear of crop-raiding •  Snare traps and shell casings found at Bechati, none at Andu (Figure 3.1) •  Human/primate landscape too dangerous for terrestrial chimpanzee nest construction at Bechati, however there is no apparent human risk in Andu (Figure 3.2)

Figure 3.1 Snare trap (Bechati, LMFL, Cameroon) Figure 3.2 Andu Palace (Andu, LMFL, Cameroon)

Future Research •  Future research on chimpanzee nest construction in the LMFL needs to focus on collecting more data on potential non-human predators (i.e., leopards) •  More data on terrestrial nests need to be collected during both the rainy and dry seasons •  The hypothesis proposed here needs to be applied to other forest blocks within the LMFL to see if it is applicable throughout the region •  Research needs to assess what socio-cultural factors play a role in terrestrial nest construction

Chimpanzee Nest Data

References Boesch, C. (1995). Innovation in Wild Chimpanzees (Pan troglodytes). International Journal of Primatology, 16(1), 1-16. Boesch, C. (2003). Is Culture a Golden Barrier Between Human and Chimpanzee? Evolutionary Anthropology, 12, 82-91. Fruth, B., & Hohmann G. (1993). Ecological and Behavioural Aspects of Nest Building in Wild Bonobos. Ethology, 94, 113-126. Fruth, B., & Hohmann G. (1994). Comparative Analyses of Nest Building Behaviour in Bonobos and Chimpanzees. In Richard Wrangham, et al. (Ed.), Chimpanzee cultures (pg. 109-128). Chicago: Harvard University Press. Fruth, B., & Hohmann G. (1996). The Great Leap Forward? In William C. McGrew, et al., (Ed.), Great Ape Societies (pg. 225-240). Cambridge :Cambridge University Press. Hirata, S., et al. (1998). Use of leaves as cushions to sit on wet ground by wild chimpanzees. American Journal of Primatology, 44(3), 215-220. Humle, T., & Matsuzawa, T. (2001). Behavioural Diversity among the Wild Chimpanzee Populations of Bossou and Neighbouring Areas, Guinea and Cote d’Ivoire, West Africa. Folia Primatology, 72, 57-68. Koops, et al. (2007). Ground-nesting by the chimpanzees of the Nimba Mountains, Guinea: environmentally or socially determined? American Journal of Primatology, 69(4), 407-419. Lebialem Highlands. 2010. Retrieved October 15, 2010, from http://www.erudefconservation.org/Lebialem%20Highlands.html Matsuzawa, T., & Yamakoshi, G. (1996). Comparison of chimpanzee material culture between Bossou and Nimba. In Anne Russon, et al. (Ed.), Reaching Into Thought: The Minds of the Great Apes (pp. 211-234). New York: Cambridge University Press. McGrew, W.C. (2004). The Cultured Chimpanzee: Reflections on Cultural Primatology. New York: Cambridge University Press. Pruetz, et al. (2008). Arboreal nesting as anti-predator adaptation by savanna chimpanzees (Pan troglodytes verus) in southeastern Senegal. American Journal of Primatology, 70(4), 393-401. Reynolds, A., & Reynolds, V. (1997). Nesting Behaviour of Chimpanzees: Implications for Censuses. International Journal of Primatology, 18(4), 475-485. Sanz, C. et al. (2007). Distinguishing between the nests of sympatric chimpanzees and gorillas. Journal of Applied Ecology, 44(2), 263-272. Socio-economics. 2010. Retrieved October 15 2010, from http://www.erudefconservation.org/Socio-%20economics.html Stewart, F.A. et al. (2007). Do chimpanzees build comfortable nests? American Journal of Primatology, 69(8), 930-939. Whiten, A. et al. (1999). Culture in Chimpanzees. Nature, 399, 682-685.

Figure 2 – Map of Southwest Cameroon showing the location of the Lebialem-Mone Forest Landscape (LMFL), with the forest blocks of Bechati (yellow arrow) and Andu (red arrow) indicated.