Title Author(s) Citation Issue Date <Note> First Assessment of Chimpanzee (Pan troglodytes troglodytes) density and bedding behaviour in the Pongara National Park, Gabon Petre, Charles-Albert; Huynen, Marie-Claude; Beudels-Jamar, Roseline Pan Africa News (2007), 14(2): 22-27 2007-12 URL http://hdl.handle.net/2433/143482 Right Copyright © Pan Africa News. Type Article Textversion publisher Kyoto University 22 Pan Africa News, 14(2), December, 2007 <NOTE> First Assessment of Chimpanzee (Pan troglodytes troglodytes) density and bedding behaviour in the Pongara National Park, Gabon 23 Pan Africa News, 14(2), December, 2007 Charles-Albert Petre1, Marie-Claude Huynen1, Roseline Beudels-Jamar2 the swamp flooded forest along the south bank of the 1.Faculty of Sciences , University of Liège, Belgium firma forest. The climate is characterized by a dry season 2. Dpt. Conservation Biology, Royal Belgian Institute of Natural Sciences, Belgium Komo River. Small savannahs are dispersed into the terra from June to September and a rainy season from October to May, with a drier period in January and February. The INTRODUCTION The population size of Pan troglodytes in Equatorial Africa is estimated at 105,000 chimpanzees1. In 1984, Tutin and Fernandez2 obtained an estimation of 64,000± mean annual rainfall is 3,000 mm and the mean temperature is 26°C. The topography is relatively flat with the highest point culminating at about 40 m above sea level5. 13,000 chimpanzees for the Gabonese population, while in 2000 Walsh et al.3 observed a decline of 56% based on this previous national census. Unfortunately, those estimations are based on few studies and may not reveal the real population status. The chimpanzee population (Pan troglodytes troglodytes) of the Pongara National Park was first documented in 20064. This Park was created in 2002 especially to protect the egg-laying sites of the leatherback turtles (Dermochelys coriacea), but contains also a wide variety of mammal species, including chimpanzees. Gorillas seem to be absent, which was confirmed by the villagers inhabiting the park. METHODS Study area Pongara National Park (PNP) in Gabon is at only 15 km from Libreville, on the other bank of the Komo Estuary Fig. 2 Sampling design of the terra firma forest. (Fig. 1). This park of 929 km² is formed by the Atlantic coastal forest of the Pongara peninsula to the west, and by Transects Data were collected from January to April 2007. To assess the chimpanzee density, we opted for the Standing Crop Bed (=Nest) Count Method as the best compromise between the time and means available and the precision required for this study6,7,8. A total of 41.16 km in 17 line transects (mean length: 2.4 km; [1.8-3.3]) distant of at least 500 m from each other, were covered in the terra firma of the Pongara peninsula (Fig. 2). They were walked once following fix compass bearing adjusted on S-W 150°. All ape and human signs encountered along transects, as well Fig. 1 Pongara National Park map. as vegetation changes were noted and mapped using a 24 Pan Africa News, 14(2), December, 2007 Garmin GPSmap 60 Cx. We considered arbitrarily as a group of beds all the beds of the same age in a circle of 30 m diameter. For each group of beds, we noted the GPS coordinates, the number of beds, their perpendicular distance from the transect, their age, height, diameter, their type of construction, the tree species in which they were built, and the habitat type and characteristics of the site. Chimpanzee bed We used four ages classification based on the bed decomposition state 2: • • • • “Fresh”: the vegetation is green, sometimes with moist dung present and gorilla/chimpanzee odour, “Recent”: the vegetation is drier but the leaves remain in majority green, “Old”: the vegetation is dead but the bed shape remains distinguishable, “Very old”: no more leaves on stems and the bed is deformed and incomplete. Fig. 3 Repartition of the chimpanzees bedding sites in the study area. We distinguished two types of bed construction: • • “Tree bed”: the bed is constructed in tree, exclusively with woody materials, “Liana bed”: the bed is constructed in lianas, exclusively with woody materials. bed groups from the transect line to determine a detection function and the effective strip width (w). The « Half-Normal » model adjusted by the « Cosines » function was used to fit bed group data. In order to obtain a better Density assessment The line transect census was carried out using the method described by Tutin and Fernandez2. Assuming that every weaned chimpanzee build a new bed every night, the density of weaned individuals is: fitting of the detection function to the bed group, 5% of the data corresponding to the highest perpendicular distances were taken out9. We also reduced the density calculated by 20% to take into account the day bedding activity of the chimpanzee10,11. D = n×mean bed group size / (2wL×mean bed life span) Where n = total number of bed group; w = effective strip width; L = total transect length. RESULTS Chimpanzee density and bed distribution The DISTANCE sampling program (5.0 version) Along the transects, we encountered 51 bed groups, uses the perpendicular distances of the first bed seen of the for a total of 101 beds (Fig. 3). After the 5% data truncation, DISTANCE sampling program has calculated a Table 1 Details of the density assessment by Distance Sampling Program. Object n ESW MGS r CV(r) IC 95% (r) D CV(D) IC 95% (D) Site Nid Ind. 48 98 - 13.49 - 2.04 1.17 2.38 - 0.31 - 0.61-2.22 - 48.137 95.310 0.839 0.385 0.398 0.398 19.873-90.179 42.632-201.548 0.386-1.823 n = number of object , ESW = Effective Strip Width, MGS = mean group size; r = encounter rate (object/km), CV = coefficient of variation, IC = confidence interval, D = density (object/km²). 25 Pan Africa News, 14(2), December, 2007 density of 0.839 weaned chimpanzees/km², which 13.4 m [4-34 m]. Their mean diameter was of 50.3± 17.1 becomes 0.671 weaned chimpanzees/km² after the cm [20-130 cm], all the bed ages confounded, and reduction of 20% (Table1). 68.9±11.7 cm (n=9, [55-130 cm]) when only fresh and The clumped distribution of the bed groups shows recent beds are taking into account. Their physical at least two groups of chimpanzees, each bedding in a characteristics confirmed that all the beds were built by different habitat type. The northern chimpanzee’s group of chimpanzees, except a 130 cm wide bed which could meet the peninsula, which is the largest, beds in what we can the gorilla bed criteria. described as an old secondary forest, while the southern For the 107 arboreal beds, 92 tree identifications group beds in a dense undisturbed forest. Right down the could be done, counting for 21 species. The utilization old secondary forest is a stand of open forest with frequency for bedding varies between the tree species and Podococcus where no bed was found. is not related to the abundance of those trees in the park (0.1<P<0.2, R=0.293, N=21, Rho of Spearman) suggesting Bedding behaviour During the sampling of the terra firma forest ten additional beds were found while walking between transects and were included to determine the bedding that tree species is specifically selected by chimpanzees for bedding (Table 2). Human activity behaviour. Among the 111 beds encountered, 4 were built We found a guild of in lianas and 107 in trees, all found at a mean height of human indices in the area Table 2 List of trees used for bed construction and comparison between their frequency of utilization for bedding and their abundance in the Park. Table 3 Human indices met in the Park. Human indices N Traps 21 sampled (Table 3). Most of Fireshots 4 them can be attributed to Cases of cartridge 5 Camp of Poachers 1 poaching Machete cuts 22 Carcass of elephant 1 Chain saw noises 4 Firecamp 1 and show dichotomized a clumped Species N Utilization for bedding (%) Abundance (%) Anisophyllea purpurascens 6 6.5 3.5 Anthonota macrophylla 2 2.2 7.1 Antidesma vogelianum 1 1.1 1.7 Cola nitida 14 15.2 2.7 Coula edulis 21 22.8 3.1 Dacryodes cfr klaineana 1 1.1 3.9 Diospyros iturensis 1 1.1 2.3 Gambeya boukoukouensis 3 3.3 1.4 Irvingia gabonensis 15 16.3 3.3 Park lives in density comparable with other Gabonese and Maesobotrya klaineana 1 1.1 3.7 Central African parks more isolated from towns (Table 4). Maranthes gabunensis 7 7.3 0.4 3 3.3 1.6 We have to note, however, that certain factors may bias the Maranthes glabra Maranthes sp. 2 2.2 0.2 density calculated. Chimpanzees are known to re-use beds8 Oncoba glauca 1 1.1 0.8 which reduces the density calculated, and the bed life span Pentaclethra macrophylla 3 3.3 1.7 used Phyllocosmus calothyrsus 1 1.1 2.3 Plagiostyles africana 2 2.2 0.4 Rhabdophyllum arnoldianum 1 1.1 0.0 Scottellia sp. 3 3.3 2.7 Scyphocephalium mannii 2 2.2 1.4 then the mean bed life span might be smaller and the Staudtia gabonensis 2 2.2 1.9 density calculated higher. repartition at the surrounding of the arm of the Komo River and of the road crossing the forest from the North-East to the middle-West (Fig. 4). DISCUSSION The chimpanzee population of the Pongara National was calculated in a forest with different environmental conditions than in the Atlantic coastal forest. The higher humidity level and rainfall of the Atlantic coastal forest make the organic matter disappear faster, 26 Pan Africa News, 14(2), December, 2007 The stand of open forest with Podococcus does not seem to be favourable for bedding, which could be related in part to the physical characteristics of this type of forest. The trees are very tall with their first branches standing Table 4 Density of weaned chimpanzees in terra firma forest in different sites of Central Africa. r D Site (bed/km) (ind./km²) CAR high, the undergrowth is very open and the tree diversity Ngotto15 could be not appropriate for chimpanzees that seem to CAMEROON 1.55 0.44 (NA) Dja Reserve17 2.10 0.79 (0.60-1.04)a select trees for bed construction. This selection was Campo Forest18 NA (0.63-0.78)b 12,13 Ma’an Forest18 NA (0.8-1.0)b documented in other studies and is believed to be based on tree’s physical factors as the foliage density13 and the CONGO Odzala NP19 13.26 2.2 (1.5-3.0)b tree architecture. In our case, another factor seems to act in Lac Télé Community Reserve16 0.65 0.1 (0.0-0.1)b this tree selection: 11 of the 21 bedding tree species GABON Lopé NP20 NA NA (0.32-0.70)b Petit Loango21 NA 0.78 (0.65-0.94)b Coula edulis, Irvingia gabonensis and Cola nitida. If we Pongara NP (this study) 2.38 0.67 (NA) admit that these items are really eaten by chimpanzees of Gabonese territory2 2.05 0.49 (0-1.78)b identified are known to be part of the chimpanzee diet, e.g., the Pongara NP, the proportion of beds observed in trees identified in other sites as “food trees” rises to 71.9%, which is statistically more than the proportion expected by Values for Gabonese territory include all types of habitats. NA: not available. a: 95% confidence interval. b: mean density (minimum and maximum mean density for different habitats). chance (χ²=9.391, df=1, P<0.05). The tree selection could be then related as well to feeding. The predominant factors Libreville2,3 and despite the encounter rate of poaching that influence the bedding-site selection in the dense signs, the density we found shows that this chimpanzee evergreen forest of Pongara could be the vegetation type population has well resisted the human pressure (as well as and the edible food availability as described in the Kalinzu stochastic events since this peninsular population of 14 Forest Reserve . chimpanzee is quite geographically isolated). This Despite the postulate stating that ape populations emphasizes the urgent need to develop a management plan decline with the proximity from big towns such as for the Park, including a specific chimpanzee protection Fig. 4 Repartition of the Human indices in the study area. Pan Africa News, 14(2), December, 2007 program and a law enforcement plan that would aim at penalising illegal activities in the Park. We propose that this preliminary study serve as the basis for a chimpanzee monitoring program in Pongara NP and to extend the sampling area to the swamp forest which could shelter other groups of chimpanzees or even gorillas 15,16,17. REFERENCES 1. Oates JE 1996. African Primates: status survey and conservation action plan, revised edition. IUCN/SSC. 2. Tutin CEG, Fernandez M 1984. Nationwide census of gorilla (Gorilla g. gorilla) and chimpanzee (Pan t. troglodytes) populations in Gabon. Am J Primatol 6: 313-336. 3. Walsh PD, Abernathy KA, Bermejo M, Beyers R, De Wachter P, Akou ME, Huijbregts B, Mambounga DI, Toham AK, Kilbourn AM, Lahm SA, Latour S, Maisels F, Mbina C, Milhindou Y, Obiang SN, Effa EN, Starkey MP, Telfer P, Thibault M, Tutin CEG, White LJT, Wilkie DS 2003. Catastrophic ape decline in western equatorial Africa. Nature 1566: 1-3. 4. Latour S 2006. Recensement d’éléphants et de grands singes dans la région du Parc National de Pongara (Gabon). Rapport Technique. The Wildlife Conservation Society, Libreville. 5. Vande Weghe JP 2005. Les Parc Nationaux du Gabon. Akanda et Pongara: plages et mangroves. The Wildlife Conservation Society, New York. 6. Hashimoto C 1995. Population census of the chimpanzees in the Kalinzu forest, Uganda: comparison between methods with nest counts. Primates 36: 477-488. 7. Tutin CEG, Parnell RJ, White LTJ, Fernandez M 1995. Nest building by lowland gorilla in the Lopé Reserve, Gabon: environmental influences and implications for censusing. Int J Primatol 16(1): 73-89. 8. Plumtre AJ, Reynolds V 1996. Censusing chimpanzees in the Budongo forest, Uganda. Int J Primatol 17: 85-99. 9. Buckland ST, Anderson DR, Burnham KP, Laake JL 1993. Distance sampling: estimating abundance of biological populations. Chapman & Hall, London & New York. 10. Marchesi P, Marchesi N, Fruth B, Boesch C 1995. Census and distribution of chimpanzees in Côte d’Ivoir. Primates 36: 61-68. 11. Ham R 1998. Nationwide chimpanzee census and large mammals survey, Republic of Guinea. MAEF, Conakry. 12. Fleury-Brugière MC 2001. Estimation préliminaire de la population de chimpanzés de la zone Intégralement Protégée-Mafou du Parc National du Haut Niger; République de Guinée. Programme AGIR, République de Guinée. 13. Brownlow AR, Plumtre AJ, Reynolds V, Ward R 2001. Sources of Variation in the Nesting Behavior of Chimpanzees (Pan troglodytes schweinfurthii) in the Budongo Forest, Uganda. Am J Primatol 55: 49-55. 27 14. Furuichi T, Hashimoto C 2004. Botanical and topographical factors influencing nesting-site selection by chimpanzees in Kalinzu Forest, Uganda. Int J Primatol 25: 755-765. 15. Gautier-Hion A, Colyn M, Gautier JP 1999. Histoire naturelle des Primates d’Afrique Centrale. ECOFAC, Libreville. 16. Brugière D, Sakom D, Sinassonasibe JP 1999. Estimation des densités et analyse du comportement nidificateur des gorilles et des chimpanzés en forêt de Ngotto, RCA. ECOFAC, Bruxelles. 17. Poulsen JR, Clark CJ 2004. Densities, Distribution, ans Seasonal Movements of Gorillas and Chimpanzees in Swamp Forest in Northern Congo. Int J Primatol 25(2): 285-306. 18. Williamson L, Usongo L 1995. Réserve de faune du Dja : recensement des populations de primates et inventaires des grands mammifères. ECOFAC, Bruxelles. 19. Matthews A, Matthews A 2004. Survey of gorillas (Gorilla gorilla gorilla) and chimpanzees (Pan troglodytes troglodytes) in Southwestern Cameroon. Primates 45: 15-24. 20. Bermejo M 1999. Status and conservation of primates in Odzala National Park, Republic of Congo. Oryx 33(4): 323-331. 21. White LTJ 1994. Biomass of rain forest mammals in the Lopé Reserve, Gabon. J Anim Ecol 63: 499-512. 22. Furuichi T, Inagaki H, Angoue-Ovono S 1997. Population density of chimpanzees and gorillas in the Petit Loango Reserve, Gabon: employing a new method to distinguish between nest of the two species. Int J Primatol 18: 1029-1046.