Comparative study in animal carcass survey methods on roads
Linear transport Infrastructures and energy (LTIe) are known since the 60’s as one of the major factors implied in the global biodiversity loss. LTIe network induces land fragmentation in smaller and more isolated zones in developed and more recently in developing countries. In this context, animals use to cross LTIe to satisfy their basic living needs and then are more or less often killed by the traffic or by the LTIe’s structural elements. Fauna road and rail casualties then result in economic damage and even danger for (road) users. This fact underlines the need to detect the road sections including most of the casualties (mortality hotspots). But among previous studies conclusions, the scientific knowledge is incomplete concerning methods of carcass surveys on LTIe, especially about the biases, the limits in use and the efficiency compared between different taxonomic groups. The economic and human costs generated by such accidents on LTIe with fauna urge to do an evaluation of the biases and to the strengthening of the methods used for hotspots of fauna mortality detection.
Aim of the study
Each survey method counting carcasses LTIe show limits in use, advantages and disadvantages. The aim of this study is to compare hotspots spatial distribution and carcasses numbers (in each hotspot and in each taxonomic group) obtained with the two survey methods described above, in order to identify their biases, limits of use and their possible complementarity. These analyses would allow us to strengthen and adjust these methods in order to integrate them into evaluation of the ecological permeability of most of LTIe. Thus, an evaluation of feasibility of a survey method adapted to the railway environment will be tested.
Study area - Methods:
A literature review and direct contacts with german and swiss teams managing comparable studies will be conducted. This study relies on dataset collected during an entire year (2016) using two different methods on two 40 km long road sections in the DIR Ouest road network (in Brittany, France). An ecologist from the Cerema Ouest has especially surveyed each month, all fauna carcasses among a protocol drawn by the Cerema, counting from a car driven at 40 km.h-1. These data will be compared with those collected by the DIR Ouest road patrollers who counted every days among their multiple activities. These patrollers then followed a protocol built by the Cerema Sud-Ouest and Ouest comparable to the one written by the MNHN (UMS 2006 PatriNat) for the other DIR. Statistical analyses will compare the different taxonomic groups number obtained with the two methods. The spatial distribution of LTIe casualties should form clusters including carcasses in variable numbers; comparative statistical analyses will be applied on the spatial distribution of mortality hotspots and their number of carcasses obtained with the two survey methods, analysing then the clusters of casualties with the Ripley’s K function available in Siriema and KDE+ softwares.