MAMMAL ROAD MORTALITY AND COST--BENEFIT ANALYSES OF MITIGATION MEASURES AIMED AT REDUCING COLLISIONS WITH CAPYBARA (Hydrochoerus hydrochaeris) IN SÃO PAULO STATE, BRAZIL

Abstract

We recorded 26 mammal species or species groups as roadkill along seven highways in São Paulo State, Brazil. Capybara (Hydrochoerus hydrochaeris)-vehicle collisions were the most frequently reported species and, because of their size and weight, they can cause substantial vehicle damage and are a serious threat to human safety. Other roadkilled species such as maned wolf (Chrysocyon brachyurus), giant anteater (Myrmecophaga tridactyla) and oncilla (Leopardus tigrinus) indicate there may also be a conservation concern that could warrant the implementation of mitigation measures aimed at reducing wildlife-vehicle collisions and providing safe crossing opportunities. For this paper we investigated a potential third argument for the implementation of mitigation measures: economics. We calculated vehicle repair costs associated with capybara-vehicle collisions based on interviews with personnel from car repair shops. In addition, we reviewed the effectiveness of wildlife fencing in combination with wildlife crossing structures in reducing collisions with large mammals. We then estimated the costs for four mitigation measures (fencing with and without three types of culverts). These data were used to conduct cost-benefit analyses over a 75-year period using discount rates of 1%, 3%, and 7% to identify the threshold values (in 2012 R$) above which the four individual mitigation measures start generating benefits in excess of costs. These threshold values were translated into the number of capybara-vehicle collisions that need to occur per kilometer per year for a mitigation measure to start generating economic benefits in excess of costs. For example, based on an analysis with average vehicle repair costs and a 3% discount rate, we calculated that with at least 5.4 capybara-vehicle collisions per kilometer per year, a combination of wildlife fencing and any of the three culvert types would be economically feasible. In addition, we calculated the total costs associated with capybara-vehicle collisions on seven major highways in São Paulo State, Brazil, and we compared these to the threshold values. Finally, we conducted more detailed cost analyses for the seven highways to illustrate that even though the costs for capybara-vehicle collisions may not justify the implementation of measures along an entire highway, specific locations along a highway can still exceed thresholds. We believe the cost-benefit model presented in this paper can be a valuable decision support tool to help select locations and implement mitigation measures. These measures improve human safety, are likely to benefit nature conservation, and are economically justified even based on very conservative cost-benefit analyses.We do stress though that the threshold values presented in this paper are based on a series of assumptions and estimates and that they should be taken as indicative values rather than exact values.