Comparación de métodos para estimar el tamaño poblacional del venado de las pampas (Ozotoceros bezoarticus)
Fecha
2017
Autores
Antúnez Gómez, Berta
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ISSN de la revista
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Editor
Universidad Nacional (Costa Rica). Instituto Internacional de Manejo y Vida Silvestre
Resumen
Estimar el tamaño poblacional de animales de vida silvestre es un aspecto importante en
el manejo y conservación de las especies. Son muchos los métodos de estimación de la
abundancia que son utilizados, los cuales continúan desarrollándose para mejorar la
precisión y robustez de dichos estimados. Determinar cuáles son los mejores es una
tarea que se logra realizando comparaciones entre los diferentes métodos para conocer
cuáles son más precisos, eficaces y económicos. Esto es una labor importante sobre todo
cuando se trata de especies sujetas a algún tipo de manejo o de acciones de
conservación. Evalué diferentes métodos para estimar la abundancia poblacional del
venado de las pampas (Ozotoceros bezoarticus) reintroducido en la Reserva Natural
Iberá, provincia de Corrientes, Argentina, evaluando la precisión y los errores asociados a
cada uno de ellos. Los métodos considerados fueron: 1) transectos lineales de ancho
variable basado en distancias (método de distancias), 2) marca-reavistamiento, 3) conteo
completo en mosaicos obtenidos con un vehículo aéreo no tripulado (dron), 4) conteo
completo en videos grabados con un dron y 5) conteo completo en imágenes obtenidas
desde un avión tripulado (avioneta). El método de distancias estimó la población en 70
individuos (95% IC=43-113; EE=14,9) en el área de estudio. El estimador de marcareavistamiento calculó una población de 57 individuos (95%IC=44-71; EE=6,95). Usando
el dron, el estimado obtenido con el método de conteo completo a través de mosaicos fue
de 139 individuos (95%IC=88-189; EE=25,6) y a través de videos grabados con el dron
fue de 169 individuos (95%IC=4-333; EE=83,9). El método de la avioneta falló debido al
inconveniente de georreferenciar las imágenes obtenidas, por este motivo no se obtuvo
ningún estimado. Los métodos que presentaron mejores resultados estadísticos
referentes a la precisión, fueron los métodos terrestres. El método de distancias fue el
que estimó con menor error el número de venados de las pampas en la reserva (cercano
al valor que se conoce basado en el estimado de individuos marcados con radiocollar).
Los métodos usando dron sobrestimaron la población, sin embargo, considero que el
método de grabaciones de video con dron podría ser un método adecuado para el
seguimiento de la especie en esta zona, siempre y cuando se mejore el estimado
aumentando el tamaño de muestra. La tecnología del dron permitió realizar muestreos
con menor esfuerzo humano y tuvieron menor impacto sobre el comportamiento de los
animales. Por lo tanto, recomiendo considerar este método para el plan de monitoreo de
la población, debido a la facilidad en la detección de venados, al bajo error asociado al
doble conteo de individuos y a la rapidez en proporcionar resultados.
Estimating the population size of wild animals is an important aspect in the conservation and wildlife management. There are many methods for estimating abundance that are used, which continue to be developed to improve the robustness of these estimates. Determining which methods are better than others is a task that is achieved by making comparisons between different methods, in order to know which methods are more accurate and cost effective. This is an important task especially when dealing with species subject to some type of management or conservation criteria. I evaluated different methods to estimate the population abundance of pampas deer (Ozotoceros bezoarticus) reintroduced in the Iberá Natural Reserve, province of Corrientes, Argentina, to determine the accuracy and errors associated with each one. The methods considered were: 1) linear transects of variable width based on distances (distance method), 2) mark resight, 3) complete count with an unmanned aerial vehicle (dron) through mosaics, 4) complete count with a dron through videos and 5) full count in images obtained from an airplane. The distance method estimated the population in 70 individuals (95%CI=43-113; SE=14,9) in the study area. The mark resight estimator calculated a population of 57 individuals (95%CI=44-71; SE = 6,95). Using the dron, the estimator obtained with the complete counting method through mosaics was 139 individuals (95%CI=88-189; SE=25,6) and through videos recorded was 169 individuals (95%CI=4-333;SE=83,9). The airplane method failed, due to the inconvenience of georeferencing the obtained images and I could not calculate an estimated. The methods that presented the best statistical results concerning precision were the terrestrial methods. The distances method was the one that estimated with less error the number of pampas deer in the reserve (according to the best estimate based on known radio-tagged individual). The dron-based methods overestimated the populaton size in the study area, however, I consider that the dron method through videos would be the appropriate method for tracking the species in this area, as long as the estimation is improved by increasing the sample size. The technology of the dron allowed to make surveys with less human effort and had less impact on the behavior of the animals. Therefore, I recommend this method to implement it in the monitoring plan of the population, due to the ease in detectability of pampas deer, the low error associated with double counting and the speed in providing results.
Estimating the population size of wild animals is an important aspect in the conservation and wildlife management. There are many methods for estimating abundance that are used, which continue to be developed to improve the robustness of these estimates. Determining which methods are better than others is a task that is achieved by making comparisons between different methods, in order to know which methods are more accurate and cost effective. This is an important task especially when dealing with species subject to some type of management or conservation criteria. I evaluated different methods to estimate the population abundance of pampas deer (Ozotoceros bezoarticus) reintroduced in the Iberá Natural Reserve, province of Corrientes, Argentina, to determine the accuracy and errors associated with each one. The methods considered were: 1) linear transects of variable width based on distances (distance method), 2) mark resight, 3) complete count with an unmanned aerial vehicle (dron) through mosaics, 4) complete count with a dron through videos and 5) full count in images obtained from an airplane. The distance method estimated the population in 70 individuals (95%CI=43-113; SE=14,9) in the study area. The mark resight estimator calculated a population of 57 individuals (95%CI=44-71; SE = 6,95). Using the dron, the estimator obtained with the complete counting method through mosaics was 139 individuals (95%CI=88-189; SE=25,6) and through videos recorded was 169 individuals (95%CI=4-333;SE=83,9). The airplane method failed, due to the inconvenience of georeferencing the obtained images and I could not calculate an estimated. The methods that presented the best statistical results concerning precision were the terrestrial methods. The distances method was the one that estimated with less error the number of pampas deer in the reserve (according to the best estimate based on known radio-tagged individual). The dron-based methods overestimated the populaton size in the study area, however, I consider that the dron method through videos would be the appropriate method for tracking the species in this area, as long as the estimation is improved by increasing the sample size. The technology of the dron allowed to make surveys with less human effort and had less impact on the behavior of the animals. Therefore, I recommend this method to implement it in the monitoring plan of the population, due to the ease in detectability of pampas deer, the low error associated with double counting and the speed in providing results.
Descripción
Palabras clave
VENADO DE LAS PAMPAS, CONSERVACIÓN DE LA VIDA SILVESTRE, MANEJO DE VIDA SILVESTRE, MONITOREO AMBIENTAL
Citación
Antúnez-Gómez, B. (2017). Comparación de métodos para estimar el tamaño poblacional del venado de las pampas (Ozotoceros bezoarticus). (Tesis de Maestría en Conservación y Manejo de Vida Silvestre). Universidad Nacional