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HOW MANY WILD MAMMALS ARE ROADKILLED PER YEAR IN SAO PAULO STATE, BRAZIL? AN ESTIMATE BASED ON ROADKILL DATA COLLECTED BY TOLL ROAD COMPANIES.
For wildlife species, roads have two main impacts: the barrier effect and direct death of animals through wildlife-vehicle collisions. Many studies have estimated roadkill numbers for different animal groups along roads with different characteristics and over different time periods. In this study, we analyzed medium- and large-sized mammal roadkill data from 18 toll road companies in São Paulo State, Brazil, and then extrapolated the roadkill patterns for the entire system of paved roads in the State. To estimate mammal mortality along two-lane public roads, we used roadkill data (n = 993) collected by toll road companies before they duplicated the roads from 2 to 4-lanes to estimate the number of mammal roadkills for all paved roads in São Paulo State. Over 10 years of roadkill monitoring on toll roads (2005-2014), 37,744 mammals were roadkilled, with a total of 32 medium- to large-sized species (average number of roadkilled individuals per year = 3,774 ± 1,159; min = 1,932; max = 5,369; 0.6 individuals roadkilled/km/year). The most roadkilled species were common and generalist mammals adapted to human-modified landscapes (HMLs) (80% of the data), but also high roadkill numbers of threatened and endangered species (4.3% of the data), which present a serious concern for conservation. Most of the reported roadkills occurred during the nocturnal period (66.03%, n = 14,189) and in rainy months (55.55%, n = 15,318). Mammal roadkills tended to increase between 2009 and 2014 (R2 = 0.614; p = 0.065), with an average increase of 313.5 individuals per year. Extrapolating the results for the entire São Paulo State, resulted in an average estimate of 39,605 medium- and large-sized mammals roadkilled per year. It is recommendable to make a caveat for specific species that were under or overestimated in this study. Our findings permit to direct studies with specific species in order to understand the extinction risk of mammal populations and to subsidize the development of more precise action plans.
Roadkill, mammal, roads, São Paulo state, estimate
We thank the Wildlife Ecology, Management and Conservation Lab (LEMaC), Forest Science Department (Escola Superior de Agricultura “Luiz de Queiroz”, Universidade de São Paulo), the Interdisciplinary Program in Applied Ecology (PPGI-EA), and the São Paulo Research Foundation (Fundação de Amparo à Pesquisa do Estado de São Paulo) for the visiting professor grant for Dr. Marcel Huijser (FAPESP grant 2017/01686-4). We thank the National Council of Technological and Scientific Development (CNPq) for the productivity fellowship granted to KMPMBF (#308503/2014-7 and 308632/2018-4) and we also thank ARTESP to provide roadkill data from toll road companies in São Paulo state.
Biologia da Conservação
FERNANDA DELBORGO ABRA, MARCEL PIETER HUIJSER, MARCELO MAGIOLI, ALEX BOVO, KATIA FERRAZ