Carcass Persistence and Detectability: Reducing the Uncertainty Surrounding Wildlife-Vehicle Collision Surveys.
Carcass persistence time and detectability are two main sources of uncertainty on roadkill surveys. In this study, we evaluate the influence of these uncertainties on roadkill surveys and estimates. To estimate carcass persistence time, three observers (including the driver) surveyed 114km by car on a monthly basis for two years, searching for wildlife-vehicle collisions (WVC). Each survey consisted of five consecutive days. To estimate carcass detectability, we randomly selected stretches of 500m to be also surveyed on foot by two other observers (total 292 walked stretches, 146 km walked). We expected that body size of the carcass, road type, presence of scavengers and weather conditions to be the main drivers influencing the carcass persistence times, but their relative importance was unknown. We also expected detectability to be highly dependent on body size. Overall, we recorded low median persistence times (one day) and low detectability (<10%) for all vertebrates. The results indicate that body size and landscape cover (as a surrogate of scavengers' presence) are the major drivers of carcass persistence. Detectability was lower for animals with body mass less than 100g when compared to carcass with higher body mass. We estimated that our recorded mortality rates underestimated actual values of mortality by 2-10 fold. Although persistence times were similar to previous studies, the detectability rates here described are very different from previous studies. The results suggest that detectability is the main source of bias across WVC studies. Therefore, more than persistence times, studies should carefully account for differing detectability when comparing WVC studies.
Department of Zoology, University of Brasília-UnB, Brasília, Federal District, Brazil.|Centre for Ecology, Evolution and Environmental Changes, Faculty of Sciences, University of Lisbon, Lisbon, Portugal.|IBRAM-Instituto Brasília Ambiental, Brasília, Federal District, Brazil.
Rodrigo Augusto Lima
RA
Santos
CIBIO-UE-Research Centre in Biodiversity and Genetic Resources, Pole of Évora, Research Group in Applied Ecology, University of Évora, Évora, Portugal.|UBC-Conservation Biology Lab, Department of Biology, University of Évora, Évora, Portugal.
Sara M
SM
Santos
Centre for Ecology, Evolution and Environmental Changes, Faculty of Sciences, University of Lisbon, Lisbon, Portugal.
Margarida
M
Santos-Reis
Department of Zoology, University of Brasília-UnB, Brasília, Federal District, Brazil.|IBRAM-Instituto Brasília Ambiental, Brasília, Federal District, Brazil.
Almir
A
Picanço de Figueiredo
Department of Biology, Federal University of Lavras, Lavras, Minas Gerais, Brazil.
Alex
A
Bager
Department of Zoology, University of Brasília-UnB, Brasília, Federal District, Brazil.
Ludmilla M S
LM
Aguiar
Infraestruturas de Portugal BiodiversityChair. CIBIO/InBio, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto. Campus Agrário de Vairão, Vairão, Portugal.|CEABN/InBio, Centro de Ecologia Aplicada "Professor Baeta Neves", Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal.
Fernando
F
Ascensão
D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D000818:Animals; D000835:Animals, Wild; D049628:Body Size; D002102:Cadaver; D012307:Risk Factors; D011795:Surveys and Questionnaires; D035501:Uncertainty; D014887:Weather