Assessing the relative effect of road- and carcass-related factors on searcher efficiency: implications for future roadkill monitoring programmes.

Carcass counts along roads can notably underestimate the number of wildlife casualties due to several sources of bias, including observers’ inability to detect carcasses during the surveys. A wide range of road-type and carcass-related factors can affect the detection efficiency by the observers, particularly when looking for small-sized species, such as amphibians, small mammals and reptiles. To assess the relative importance of factors such as road type (in terms of width and traffic volume), observer, carcass type and its condition as well as the location of the carcass, we carried out searcher-efficiency trials on two paved two-lane roads located in central Portugal, namely on a(i) national road, with wide lanes and shoulders (daytime traffic: ~22.8 vehicles/hour); and on a(ii)secondary road, with narrow lanes and without shoulders (daytime traffic: ~2.7 vehicles/hour). Each road was divided into 12sectionscomprising 500m in length (spaced at least 250m apart) along which carcasses of passerines were randomly placed (7-10 carcasses per section). In addition, bat carcasses were also randomly placed along the National road (3-5 carcasses per section).The trials were then completed by four independent, similar experienced observers driving a vehicle at 30-40km/hour that recorded the trial carcasses detected. All observers were accompanied (on the passenger seat) by the researcher who previously placed the carcasses, to check for their presence, current status (e.g. intact, flattened, only feathers) and position on the road (e.g. left lane, center line, right shoulder, verge). Our preliminary results show that bat carcasses are far more difficult to detect (detection rate: 0.28; 95% CI: 0.18 - 0.41) than passerines (detection rate: 0.69; 95% CI: 0.62 - 0.76). Carcass position and status seems to significantly affect the detection rates of passerines at the National road, but not in the Secondary road (except if carcasses fall on road verges). In both types of roads, the observers seem to detect carcasses of passerines equally well. The same did not happen with bat carcasses, with different observers showing considerably different detection rates. On average, almost half of the carcasses (43.6%) were removed before the arrival of the first observer (i.e., ~3 hours after its placement on the asphalt). Carcass disappearance resulting from traffic or scavengers can, therefore, negatively impact the robustness of the searcher-efficiency trials and, ultimately, the accuracy of the carcass detection rates obtained. We provide suggestions to minimize this issue as well as to improve the design of carcass detection trials in future roadkill monitoring programmes.

Datos y Recursos

Cite como

Bernardino J. Bispo R. Moreira F. y Santos S. Assessing the relative effect of road- and carcass-related factors on searcher efficiency: implications for future roadkill monitoring programmes. Infrastructure & Ecology Network Europe, 2021.

Clipboard Icon
Recuperado: 05 Nov 2025 22:08:13

Metadatos
Descargar
DCAT-AP/NTI-RISP

Información básica
Tipo de recurso Texto
Fecha de creación 23-05-2025
Fecha de última modificación 23-05-2025
Mostrar histórico de cambios
Identificador de los metadatos d3af3fbe-7719-5ef3-a7dd-f7e2b2e34183
Idioma de los metadatos Español
Temáticas (NTI-RISP)
Categoría del conjunto de alto valor (HVD)
Categoría temática ISO 19115 biota
URI de palabras clave
Información bibliográfica
Nombre del autor Bernardino, J., Bispo, R., Moreira, F. y Santos, S.
Nombre del editor Infrastructure & Ecology Network Europe
Identificador alternativo ISBN: 978-972-778-182-9
Identificador del autor
Email del autor
Web del autor
Procedencia
Declaración de linaje
Perfil de Metadatos
Notas sobre la versión
Versión