Spatio-temporal variation of roadkills show mass mortality events for amphibians in a highly trafficked road adjacent to a national park, Costa Rica

Abstract

Abstract:Roads have detrimental impacts on wildlife populations around the world. Specifically, roads pose direct and indirect threats to wildlife by limiting dispersal movements or through vehicle-related mortality. The rate of wildlife mortality varies both in time and space depending on the landscape composition and the type and use of road infrastructure. The objective of this study was to investigate spatiotemporal variation of vertebrate mortality in a 4 km segment of the 34 national road, adjacent to Carara National Park, Costa Rica. We conducted 81 roadkill surveys by car and bicycle from June 2010 to May 2011, georeferenced the locations of the kills and identified them to the lowest possible taxonomic level. We recorded a total of 4 709 road-killed animals of at least 58 species of vertebrates during the whole study. Amphibians accounted for 93.5 % of all the vertebrate losses and showed strong spatiotemporal variation of mass mortality events. Reptiles, especially snakes, were the second most affected taxon followed by mammals and birds. Relative mortality per day in the 4 km segment was 125.4 amphibians, 4.6 reptiles, 2.7 mammals, 1 bird and 0.46 undetermined. Road proximity to the border of the park, traffic volumes and lack of enforcement of speed limits may influence the high rate of roadkills found. We suggest the reinforcement of speed limits, wildlife crossing signage and the retrofitting of the existing culverts as under passes for animals to minimize vertebrate mortality at the road adjacent to Carara National Park. Rev. Biol. Trop. 65 (4): 1261-1276. Epub 2017 December 01.Key words: amphibian mass-kill, animal-vehicle collisions, conservation areas, extinction threat, tropical forest.Road networks are human extensions that facilitate transportation and economic development. However, the construction and the use of roads generate a broad range of negative effects, including habitat loss, fragmentation, the emissions of chemicals and noise pollution (reviews in Forman et al., 2003;Coffin, 2007;Van der Ree, Smith, & Grilo, 2015). Furthermore, roads may limit or preclude animal dispersal (e.g. Mader, Schell, & Kornacker, 1990;Clarke, White, & Harris, 1998;Develey & Stouffer 2001;Colchero et al., 2010;Long, Diefenbach, Wallingford, & Rosenberry, 2010) and induce mortality through vehicle-animal collisions (reviews in Forman & Alexander, 1998;Forman et al., 2003;Coffin, 2007;Van der Ree et al., 2015).Although the road-automobile system is a relatively recent source of wildlife mortality, it accounts for millions of roadkills every year in different latitudes, and may well exceed natural mortality rates in certain populations (Forman & Alexander, 1998 (Bissonette, 2002) and 80 million birds (Erickson, Johnson, & Young Jr., 2005) in the United States. These numbers illustrate the magnitude of this human induced phenomenon.The frequency at which animals of different taxonomic groups are reported to be killed on roads varies greatly. After reviewing several early roadkill studies conducted during the ...

Road Encroachment Near Protected Areas Alters the Natural Soundscape Through Traffic Noise Pollution in Costa Rica

“…Clearly, this proximity condition is expected to exacerbate the negative effects roads exert on wildlife. For instance, an estimated number of 4709 vertebrates were killed by vehicles, particularly amphibians, in Carara National Park during a year period study (Arévalo et al 2017).…”

“…The Costa Rican road network is comprised of approximately 40 000 km of roads, of which about 10 000 km are paved (Transportation National Plan of Costa Rica, 2011). Although there have been some concerns about the effects of roads on wildlife mortality (Arévalo et al, 2017;Monge-Ná-jera, 1996;Pomareda, 2012;Rojas-Chacón, 2011); there are no studies regarding road proximity, volumes of traffic or the effect of noise in protected areas in Costa Rica, to our knowledge.…”

Peer Review #1 of "Daytime driving decreases amphibian roadkill (v0.1)"

“…Moreover, amphibians are one of the most threatened vertebrate groups (Stuart et al, 2004), with nearly 40% of living amphibian species in danger of extinction (IUCN, 2011). Amphibians have several unique life-history or behavioural traits, such as seasonal migrations (e.g., from overwintering sites to aquatic breeding sites; Orlowski, 2007;Semlitsch, 2008;Hartel et al, 2009;Andrews, Nanjappa & Riley, 2015), relatively slow movement (Carr & Fahrig, 2001;Puky, 2005;Garrah, 2012;Hamer, Langton & Lesbarrères, 2015), and the tendency to remain immobile in response to oncoming vehicles (Mazerolle, 2005;Rytwinski & Fahrig, 2012;Lima et al, 2015), which make them more prone to road-kill events than most other vertebrate species when crossing roads (Hels & Buchwald, 2001;Gryz & Krauze, 2008;Matos, Sillero & Argana, 2012;Alroy, 2015;Heigl et al, 2017).Additionally, because of their small body size, they are difficult for drivers to see, which increases the number of collision events (Andrews, Nanjappa & Riley, 2015;Arévalo et al, 2017). Hence, the extensive amounts of road mortality resulting from the pervasiveness of roads have prompted road planners and ecologists to implement mitigation measures to offset the negative effects that roads have on wildlife (Costa, Ascensao & Bager, 2015).…”

“…Finally, although there are a number of studies on assessment of the influences on amphibians during certain traffic volume periods (Mazerolle, 2004;Sutherland, Dunning & Baker, 2010;Arévalo et al, 2017), few similar studies have been performed in China. For instance, Hels and Buchwald (2001) conducted a study on the peninsula of Djursland, where they examined the diurnal variations in the amphibian fraction of road kill and found that amphibian road mortality reached its highest peak after sunset, which may be attributable to their activity patterns.…”

What can we learn about wildlife killed by vehicles from a citizen science project? A comparison of scientific and amateur tropical roadkill records

“…After a 15-year hiatus, Costa Rican roadkill research revived in a variety of studies about which species were more affected, mortality rates and remediation options (e.g. Rojas, 2011;Araya-Gamboa & Salom-Pérez, 2013;Arévalo et al, 2017).…”