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The Influence of Transect Use by Local People and Reuse of Transects for Repeated Surveys on Nesting in Western Lowland Gorillas (Gorilla gorilla gorilla) and Central Chimpanzees (Pan troglodytes troglodytes) in Southeast Cameroon

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Monitoring populations of endangered species over time is necessary to guide and evaluate conservation efforts. This is particularly important for nonprotected areas that ensure connectivity between protected populations but are prone to uncontrolled hunting pressure. We investigated whether use of transects by local people and transect reuse for repeated surveys influence great ape nesting and bias results. We conducted simultaneous marked nest count surveys over 12 mo on established and newly opened transects in a nonprotected area subject to traditional heavy use by local people and recorded forest composition and signs of human activity. Chimpanzee and gorilla density estimates and encounter rates per kilometer were lower on established transects than on new ones. A generalized linear model indicated that hunting activity, distance to a regularly used forest trail, and transect type (old or new) predicted chimpanzee nest abundance, and distance to the trail and transect type predicted gorilla nest abundance, with no effect of habitat type (percentage suitable habitat) for either species. We, therefore, suggest that the difference in great ape nesting is a result of high levels of hunting by local people on established transects and forest trails. Our results support the use of repeated line transect surveys for monitoring great ape populations in many circumstances, although we advocate taking precautions in nonprotected areas, to avoid the bias imposed by use of established transects for hunting.

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  1. Arnhem, E., Dupain, J., Vercauteren, D. R., Devos, C., & Vercauteren, M. (2008). Selective logging, habitat quality and home range use by sympatric gorillas and chimpanzees: a case study from an active logging concession in Southeast Cameroon. Folia Primatologica, 79, 1–14.

  2. Basabose, A. K., & Yamagiwa, J. (2002). Factors affecting nesting site choice in chimpanzees at Tshibati, Kahuzi-Biega National Park: influence of sympatric gorillas. International Journal of Primatology, 23, 263–282.

  3. Blom, A., van Zalinge, R., Mbea, E., Heitkoninig, I. M. A., & Prins, H. H. T. (2004). Human impact on wildlife populations within a protected Central African forest. African Journal of Ecology, 42, 23–31.

  4. Buckland, S. T., Anderson, D. R., Burnham, K. P., & Laake, J. L. (1993). Distance sampling: Estimating abundance of biological populations. London: Chapman and Hall. Free download available at: http://www.ruwpa.st-and.ac.uk/distance.book/.

  5. Buckland, S. T., Anderson, D. R., Burnham, K. P., Laake, J. L., Borchers, D. L., & Thomas, L. (2001). Introduction to distance sampling. Oxford: Oxford University Press.

  6. Campbell, G., Kühl, H., N’Goran, P., & Boesch, C. (2008). Alarming decline of West African chimpanzees in Cote d’Ivoire. Current Biology, 18(19), R903/04.

  7. Carroll, R. W. (1988). Relative density, range extension, and conservation potential of the lowland gorilla (Gorilla gorilla gorilla) in the Dzanga-Sangha region of southwestern Central African Republic. Mammalia, 52(3), 309–323.

  8. Chazdon, R. L., Harvey, C. A., Komar, O., Griffith, D. M., Ferguson, B. G., et al. (2009). Beyond reserves: a research agenda for conserving biodiversity in human-modified tropical landscapes. Biotropica, 41, 142–153.

  9. Cipoletta, C. (2003). Ranging patterns of a western gorilla group (Gorilla gorilla gorilla) during habituation to humans in the Dzanga-Ndoki National Park, Central African Republic. International Journal of Primatology, 24(6), 1207–1226.

  10. Clark, C. J., Poulsen, J. R., Malonga, R., & Elkan, P. W. (2009). Logging concession can extend the conservation estate for Central African tropical forests. Conservation Biology, 23(5), 1281–1293.

  11. Dupain, J. (2001). Conservation of great apes on the periphery of the Dja Reserve. Gorilla Journal, 23, 18–20.

  12. Dupain, J., Bombome, K., & Van Elsacker, L. (2003). Les chimpanzés et les gorilles de la reserve de faune du Dja. Canopée, 24, 14–15.

  13. Dupain, J., Guislain, P., Nguengang, G. M., De Vleeschouwer, K., & Van Elsacker, L. (2004). High chimpanzee and gorilla densities in a non-protected area of the northern periphery of the Dja faunal reserve, Cameroon. Oryx, 38(2), 1–8.

  14. Ekobo, A. (1998). Large mammals and vegetation surveys in the Boumba-bek and Nki Project Area. Yaoundé: WWF-CPO.

  15. Furuichi, T., Hashimoto, C., & Tashiro, Y. (2001). Extended application of a marked-nest census method to examine seasonal changes in habitat use by chimpanzees. International Journal of Primatology, 22(6), 913–928.

  16. Hashimoto, C. (1995). Population census of the chimpanzees in the Kalinzu Forest, Uganda: Comparison between methods with nest counts. Primates, 36, 477–488.

  17. Hutter, C. (2000). An overview of logging in Cameroon. Washington, DC: World Resources Institute.

  18. Kano, T., & Asato, R. (1994). Hunting pressure on chimpanzees and gorillas in the Motaba River area, northeastern Congo. African Study Monographs, 15, 143–162.

  19. Kühl, H., Maisels, F., Ancrenaz, M., & Williamson, E. A. (2008). Best practice guidelines for surveys and monitoring of great ape populations. Gland: IUCN SSC Primate Specialist Group (PSG).

  20. Letouzey, R. (1985). Notice de la carte phytogéographique du Cameroun au 1/500 000. Domaine de forêt dense humide toujours verte. Toulouse: Institut de la Carte Internationale de la Végétation.

  21. Marchesi, P., Marchesi, N., Fruth, B., & Boesch, C. (1995). Census and distribution of chimpanzees in Cote D’Ivoire. Primates, 36, 591–607.

  22. Matthews, E., & Matthews, A. (2004). Survey of gorillas (Gorilla gorilla gorilla) and chimpanzees (Pan troglodytes troglodytes) in Southwestern Cameroon. Primates, 45, 15–24.

  23. McNeilage, A. (1995). Mountain gorillas in the Virunga Volcanoes: Ecology and carrying capacity. Ph.D. thesis, University of Bristol.

  24. McNeilage, A., Robbins, M. M., Gray, M., Olupot, W., Babaasa, D., Bitariho, R., et al. (2006). Census of the mountain gorilla Gorilla beringei beringei population in Bwindi Impenetrable National Park, Uganda. Oryx, 40, 419–427.

  25. MINFOF. (2011). Liste des Aires Proteges Classes du Cameroun 2011, internal report.

  26. Morgan, D., & Sanz, C. (2007). Best practice guidelines for reducing the impact of commercial logging on great apes in Western Equatorial Africa. Gland: IUCN SSC Primate Specialist Group (PSG).

  27. Morgan, D., Sanz, C., Onononga, J. R., & Strindberg, S. (2006). Ape abundance and habitat use in the Goualougo Triangle, Republic of Congo. International Journal of Primatology, 27(1), 147–179.

  28. Muchaal, P. K., & Nandjui, G. (1999). Impact of village hunting on wildlife populations in the Western Dja Reserve, Cameroon. Conservation Biology, 13(2), 385–396.

  29. Ndobe, S. N. (2007). Still waiting for the benefits: An analysis of the ECOFAC’s “Mesures d’accompagnement” project on the local and indigenous communities of the Dja Biosphere Reserve, Cameroon. Report CED/FERN. Available at: http://www.fern.org/sites/fern.org/files/still%20waiting%20for%20the%20benefits.pdf.

  30. Plumptre, A. J. (2000). Monitoring mammal populations with line transect techniques in African forests. Journal of Applied Ecology, 37, 356–368.

  31. Plumptre, A. J., & Cox, D. (2006). Counting primates for conservation: primate surveys in Uganda. Primates, 47, 65–73.

  32. Plumptre, A. J., & Reynolds, V. (1994). The effect of selective logging on the primate populations in the Budongo Forest Reserve, Uganda. Journal of Applied Ecology, 31(4), 631–641.

  33. Plumptre, A. J., & Reynolds, V. (1996). Censusing chimpanzees in the Budongo Forest, Uganda. International Journal of Primatology, 17(1), 85–99.

  34. Plumptre, A. J., & Reynolds, V. (1997). Nesting behavior of chimpanzees: implications for censuses. International Journal of Primatology, 18, 475–485.

  35. Poulsen, J. R., & Clark, C. J. (2004). Densities, distributions and seasonal movements of gorillas and chimpanzees in swamp forest in Northern Congo. International Journal of Primatology, 25(2), 285–306.

  36. Rabanal, L. I., Kühl, H. S., Mundry, R., Robbins, M. M., & Boesch, C. (2010). Oil prospecting and its impact on large rainforest mammals in Loango National Park, Gabon. Biological Conservation, 143, 1017–1024.

  37. Remis, M. J. (2000). Preliminary assessment of the impacts of human activities on gorillas (Gorilla gorilla gorilla) and other wildlife at Dzanga-Sangha Reserve, Central African Republic. Oryx, 34, 56–65.

  38. Sanz, C., Morgan, D., Strindberg, S., & Onononga, J.-R. (2007). Distinguishing between the nests of sympatric chimpanzees and gorillas. Journal of Applied Ecology, 44, 263–272.

  39. Stokes, E. J. (2008). Conservation through scientific collaboration: Case study—Western-gorilla.org. In T. S. Stoinski, H. D. Steklis, & P. T. Mehlman (Eds.), Conservation in the 21st century: Gorillas as a case study (pp. 296–314). New York: Springer.

  40. Stokes, E. J., Strindberg, S., Bakabana, P. C., Elkan, P. W., Iyenguet, F. C., Madzoke, B., et al. (2010). Monitoring great ape and elephant abundance at large spatial scales: measuring effectiveness of a conservation landscape. PLoS One, 5(4), e10294.

  41. Tagg, N., Petre, C.-A., & Willie, J. (2011). Evaluating the effectiveness of a 10-year old great ape conservation project in Cameroon. Pan Africa News, 18(2), 20–23.

  42. Thomas, L., Laake, J. L., Strindberg, S., Marques, F. F. C., Buckland, S. T., Borchers, D. L., et al. (2006). Distance 5.0. Release 2. Research unit for wildlife population assessment, University of St. Andrews, U.K. Available at: www.ruwpa.st-and.ac.uk/distance/.

  43. Thomas, L., Buckland, S. T., Rexstad, E. A., Laake, J. L., Strindberg, S., Hedley, S. L., et al. (2010). Distance software: design and analysis of distance sampling surveys for estimating population size. Journal of Applied Ecology, 47, 5–14.

  44. Todd, A. F., Kühl, H. S., Cipolletta, C., & Walsh, P. D. (2008). Using dung to estimate gorilla density: modeling dung production rate. International Journal of Primatology, 29, 549–563.

  45. Tutin, C. E. G. (1996). Ranging and social structure of lowland gorillas in the Lope Reserve, Gabon. In W. C. McGrew, L. F. Marchant, & T. Nishida (Eds.), Great ape societies (pp. 58–70). Cambridge: Cambridge University Press.

  46. Tutin, C. E. G., & Fernandez, M. (1984). Nationwide census of gorilla (Gorilla g. gorilla) and chimpanzee (Pan t. troglodytes) populations in Gabon. American Journal of Primatology, 6, 313–336.

  47. van der Wal, M., & Nku, E. (1999). Large mammals of the Dja Fauna Reserve: Conservation status and threats. Yaounde: The Golden Ark Foundation/IUCN – Dja MINEF.

  48. Walsh, P. D., & White, L. J. T. (1999). What will it take to monitor forest elephants? Conservation Biology, 13, 1194–1202.

  49. Walsh, P. D., Abernethy, K. A., Bermejo, M., Beyers, R., De Wachter, P., Ella Akou, M., et al. (2003). Catastrophic ape decline in western Equatorial Africa. Nature, 422, 611–614.

  50. White, L., & Edwards, A. (Eds.). (2000). Conservation research in the African rain forests: A technical handbook. New York: Wildlife Conservation Society.

  51. Williamson, L., & Usongo, L. (1995). Recensement des populations de primates et inventaire des grand mammifères; Réserve de faune du Dja, Cameroon. Yaounde: ECOFAC – Composante Cameroon.

  52. Willie, J. (2006). Contribution à l’évaluation de l’incidence de la chasse sur les populations de céphalophes de la périphérie Nord de la Réserve de Biosphère du Dja (Est-Cameroun). Université de Dschang, Cameroun. Mémoire présenté en vue de l’obtention du diplôme d’Ingénieur des Eaux, Forêts et Chasse.

  53. Willie, J., Petre, C. A., Tagg, N., & Lens, L. (2012a). Evaluation of species richness estimators based on quantitative performance measures and sensitivity to patchiness and sample grain size. Acta Oecologica, 45, 31–41.

  54. Willie, J., Petre, C. A., Tagg, N., & Lens, L. (2012b). Density of herbaceous plants and distribution of western gorillas in different habitat types in south-east Cameroon. African Journal of Ecology. doi:10.1111/aje.12014.

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We thank the Flemish Government for core funding of PGS through the Centre for Research and Conservation of the Royal Zoological Society of Antwerp and the Ministry of Forests and Wildlife and the Ministry of Research and Innovation for permission to conduct the research. We thank Charles Yem Bamo, Fabrice Ottou Mbida, Germain Mbock, and John Carlos Nguinlong for their help during surveys, and all logistic staff of PGS and local workers in the community of Malen V for their individual invaluable contributions to this work. We also specifically acknowledge Charles-Albert Petre and Patrick Guislain and the editors and two anonymous reviewers for constructive advice.

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Correspondence to Nikki Tagg.

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Tagg, N., Willie, J. The Influence of Transect Use by Local People and Reuse of Transects for Repeated Surveys on Nesting in Western Lowland Gorillas (Gorilla gorilla gorilla) and Central Chimpanzees (Pan troglodytes troglodytes) in Southeast Cameroon. Int J Primatol 34, 554–570 (2013). https://doi.org/10.1007/s10764-013-9681-0

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  • Central chimpanzee
  • Established transects
  • Marked nest count surveys
  • Nesting
  • Transect reuse
  • Western lowland gorilla