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.

Habitat or matrix: which is more relevant to predict road-kill of vertebrates?

“…The highway manager agreed to install some fences and signs where were many capybaras killed by vehicle collision (Bueno et al, 2013). Fences are cheaper than underpasses, especially because they were installed some hundred of meters near the river blocking capybaras when they tried to cross the road (Huijser et al, 2013). Some preliminary analysis showed that capybaras road-kill events were reduced in this small stretch of the highway.…”

“…A few large mammals (although smaller than large North American and European mammals) were killed by collision with vehicles, such as Hydrochoerus hydrochaeris, Cerdocyon thous and Chrysocyon brachyurus, and could cause serious accidents, including loss of human lives or substantial material damages for the driver (Huijser et al, 2013). Chrysocyon brachyurus is the only species considered near threatened for the IUCN Red List (IUCN, 2013), and thus is a conservation concern, in addition to be a security issue for drivers.…”

“…We believe that there are two main approaches to increase the relevance of road ecology in Brazil and provide the basis for negotiation with government and private companies to get mitigation measures done: security and conservation. Some large animals that may cause more severe accidents with many human causalities and financial damages, such as capybaras, should be used as flagship species for security approach (Bueno et al, 2013;Huijser et al, 2013;Simberloff, 1998). The conservation approach should be used, particularly near protected areas, focusing in biodiversity loss with a community level of analysis, and thus including as many species as possible in mitigation measures.…”

A perspectiva da mídia online sobre os acidentes entre veículos e animais em rodovias brasileiras: uma questão de segurança?

“…As passagens de fauna juntamente com alambrados para direcionar os animais para esses dutos impossibilitam que eles atravessem a pista de rolamento, ao mesmo tempo possibilitam a travessia pelos ecodutos, aumentando as chances de manter o fluxo gênico e a viabilidade das populações (Corlatti et al, 2009;Laurance et al, 2009;Holderegger & Di Giulio, 2010). O custo-benefício da construção das passagens em relação às cercas foi estimado para colisões entre veículos e capivaras, considerando apenas o custo médio do reparo do veículo, não incluindo custos associados a ferimentos e a fatalidades humanas, reboque, assistência médica no local do acidente, investigação do acidente e à remoção da carcaça do animal da rodovia (Huijser et al, 2013). Nos trechos das rodovias paulistas estudadas, onde o número de colisões entre veículos e capivaras foi mais alto, cercas e passagens de fauna por baixo da rodovia são economicamente atrativas (Huijser et al, 2013).…”

“…O custo-benefício da construção das passagens em relação às cercas foi estimado para colisões entre veículos e capivaras, considerando apenas o custo médio do reparo do veículo, não incluindo custos associados a ferimentos e a fatalidades humanas, reboque, assistência médica no local do acidente, investigação do acidente e à remoção da carcaça do animal da rodovia (Huijser et al, 2013). Nos trechos das rodovias paulistas estudadas, onde o número de colisões entre veículos e capivaras foi mais alto, cercas e passagens de fauna por baixo da rodovia são economicamente atrativas (Huijser et al, 2013). A alta morbidade das colisões entre veículos e capivaras indica que os custos de atendimento médico com os feridos e os prejuízos relacionados à perda de vidas humanas foram subestimados por Huijser et al (2013).…”