Conteo de huellas en brechas barridas: un índice de abundancia para mamíferos
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Ecología en Bolivia
Abstract
Entre los meses de julio y noviembre de 1996 se realizaron muestreos de la fauna en cuatro sitios del Chaco, provincia Cordillera, departamento Santa Cruz (18º30' a 19º45' Sur y 62º00' a 62º45' Oeste). Se elaboró un nuevo método utilizando el conteo de huellas en brechas barridas para identificar especies y para comparar abundancia relativa entre sitios. El índice de abundancia se calcula según el total de observaciones de huellas de cada especie y el total de kilómetros de brechas barridas revisadas durante el estudio. En los cuatro sitios se observaron en total huellas de 26 especies de mamíferos silvestres, excluyendo a ratones. Según la prueba de Chi-cuadrado, la diferencia es significativa (p< 0,05) entre sitios para siete especies de mamíferos: Tolypeules matacus, Cerdocyon thous, Pseudalopex gymnocercus, Tapirus terrestris, Mazama gouazoubira, Cavia aperea y Sylvilagus brasiliensis. Empleando este método, se obtuvieron 1315 observaciones de huellas sobre 379,3 km de brechas barridas, en comparación a 260 observaciones directas en 2505 km de caminatas. El método tiene algunos problemas: depende del suelo, del tiempo y del observador, algunos animales no se pueden identificar por sus huellas, otros evitan lugares abiertos, y no sirve para animales arborícolas o acuáticos. Sin embargo es un método sencillo y práctico con el cual la gente del lugar-guardaparques o cazadores por ejemplo-pueden colectar datos y monitorear la fauna para su conservación y manejo sostenible.
Between the months of July and November 1996 researchers conducted field studies of biodiversity in four sites in the Chaco, Cordillera Province, Santa Cruz Department (18° 30' to 19° 45' South and 62° 00' to 62° 45' West). They developed a new method, track counts on swept trails, to identify species and compare relative abundance between sites. The abundance index, in kilometers per observation, is calculated from total observations of tracks of each species and total kilometers of swept trails that were monitored during the study. In total in the four sites, tracks of 26 species of wild mammals, excluding rats, were identified. A chi-square analysis indicates that differences between sites are statistically significant (p≤ 0.05) for seven species: Tolypeutes matacus, Cerdocyon thous, Pseudalopex gymnocercus, Tapirus terrestris, Mazama gouazoubira, Cavia aperea, and Sylvilagus brasiliensis. Researchers recorded 1315 observations of tracks in 379.3 km of swept trails, compared to 260 direct observations of mammals in 2505 km of censuses. The method has several drawbacks: it depends on soil types and weather, it depends on the interpretation of the observers, certain mammals cannot be identified by their tracks, certain mammals avoid open areas like trails, and it does not work for arboreal or aquatic animals. Nevertheless, it is a simple and practical method with which local people-park guards or hunters for example-can collect data and monitor wildlife for conservation and sustainable use.
Between the months of July and November 1996 researchers conducted field studies of biodiversity in four sites in the Chaco, Cordillera Province, Santa Cruz Department (18° 30' to 19° 45' South and 62° 00' to 62° 45' West). They developed a new method, track counts on swept trails, to identify species and compare relative abundance between sites. The abundance index, in kilometers per observation, is calculated from total observations of tracks of each species and total kilometers of swept trails that were monitored during the study. In total in the four sites, tracks of 26 species of wild mammals, excluding rats, were identified. A chi-square analysis indicates that differences between sites are statistically significant (p≤ 0.05) for seven species: Tolypeutes matacus, Cerdocyon thous, Pseudalopex gymnocercus, Tapirus terrestris, Mazama gouazoubira, Cavia aperea, and Sylvilagus brasiliensis. Researchers recorded 1315 observations of tracks in 379.3 km of swept trails, compared to 260 direct observations of mammals in 2505 km of censuses. The method has several drawbacks: it depends on soil types and weather, it depends on the interpretation of the observers, certain mammals cannot be identified by their tracks, certain mammals avoid open areas like trails, and it does not work for arboreal or aquatic animals. Nevertheless, it is a simple and practical method with which local people-park guards or hunters for example-can collect data and monitor wildlife for conservation and sustainable use.
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No. 30