Impacts of Roads and Hunting on Central African Rainforest Mammals

Authors

  • WILLIAM F. LAURANCE,

    1. Smithsonian Tropical Research Institute, Apartado 2072, Balboa, Republic of Panamá, email laurancew@si.edu
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  • BARBARA M. CROES,

    1. Monitoring and Assessment of Biodiversity Program, National Zoological Park, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20560–0705, U.S.A.
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  • LANDRY TCHIGNOUMBA,

    1. Monitoring and Assessment of Biodiversity Program, National Zoological Park, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20560–0705, U.S.A.
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  • SALLY A. LAHM,

    1. Monitoring and Assessment of Biodiversity Program, National Zoological Park, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20560–0705, U.S.A.
    2. Institut de Recherche en Ecologie Tropicale, B.P. 180, Makokou, Gabon
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  • ALFONSO ALONSO,

    1. Monitoring and Assessment of Biodiversity Program, National Zoological Park, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20560–0705, U.S.A.
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  • MICHELLE E. LEE,

    1. Monitoring and Assessment of Biodiversity Program, National Zoological Park, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20560–0705, U.S.A.
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  • PATRICK CAMPBELL,

    1. Monitoring and Assessment of Biodiversity Program, National Zoological Park, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20560–0705, U.S.A.
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  • CLAUDE ONDZEANO

    1. Monitoring and Assessment of Biodiversity Program, National Zoological Park, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20560–0705, U.S.A.
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Abstract

Abstract: Road expansion and associated increases in hunting pressure are a rapidly growing threat to African tropical wildlife. In the rainforests of southern Gabon, we compared abundances of larger (>1 kg) mammal species at varying distances from forest roads and between hunted and unhunted treatments (comparing a 130-km2 oil concession that was almost entirely protected from hunting with nearby areas outside the concession that had moderate hunting pressure). At each of 12 study sites that were evenly divided between hunted and unhunted areas, we established standardized 1-km transects at five distances (50, 300, 600, 900, and 1200 m) from an unpaved road, and then repeatedly surveyed mammals during the 2004 dry and wet seasons. Hunting had the greatest impact on duikers (Cephalophus spp.), forest buffalo (Syncerus caffer nanus), and red river hogs (Potamochoerus porcus), which declined in abundance outside the oil concession, and lesser effects on lowland gorillas (Gorilla gorilla gorilla) and carnivores. Roads depressed abundances of duikers, sitatungas (Tragelaphus spekei gratus), and forest elephants (Loxondonta africana cyclotis), with avoidance of roads being stronger outside than inside the concession. Five monkey species showed little response to roads or hunting, whereas some rodents and pangolins increased in abundance outside the concession, possibly in response to greater forest disturbance. Our findings suggest that even moderate hunting pressure can markedly alter the structure of mammal communities in central Africa. Roads had the greatest impacts on large and small ungulates, with the magnitude of road avoidance increasing with local hunting pressure.

Abstract

Resumen: La expansión de carreteras asociada con incrementos en la presión de cacería son una amenaza creciente para la vida silvestre tropical Africana. En los bosques lluviosos del sur de Gabón, comparamos las abundancias de especies de mamíferos mayores (>1 kg) a diferentes distancias de las carreteras y entre tratamientos con y sin cacería (comparamos una concesión petrolera de 130 km2 que estaba casi totalmente protegida de la caza con áreas cercanas afuera de la concesión que tenían presión de caza moderada). En cada uno de los 12 sitios que estaban repartidos equitativamente en áreas con caza y sin caza, establecimos transectos estandarizados de 1 km a cinco distancias (50, 300, 600 900 years 1200 m) de un camino no pavimentado, y muestreamos mamíferos repetidamente durante las estaciones seca y lluviosa de 2004.La cacería tuvo el mayor impacto sobre duikers (Cephalophus spp.), búfalo de bosque (Syncerus caffer nanus) y Potamochoerus porcus, cuya abundancia declinó afuera de la concesión petrolera, y menos efectos sobre gorilas (Gorilla gorilla gorilla) y carnívoros. Los caminos deprimieron la abundancia de duikers, sitatungas (Tragelaphus spekei gratus) y elefantes (Loxondonta africana cyclotis), la evasión de caminos fue mayor afuera que adentro de la concesión. Cinco especies de monos no mostraron respuesta a los caminos o a la cacería, mientras que la abundancia de algunos roedores y pangolines aumentó afuera de la concesión, posiblemente en respuesta a una mayor perturbación del bosque. Nuestros resultados sugieren que aun la cacería moderada puede alterar significativamente la estructura de comunidades de mamíferos en África central. Las carreteras tuvieron los mayores impactos sobres ungulados grandes y pequeños, la magnitud de la evasión de caminos aumentó con la presión de cacería local.

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