Amphibians and Reptiles on roads in northeast Suffolk.

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AMPHIBIANS & REPTILES ON ROADS

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AMPHIBIANS AND REPTILES ON ROADS IN NORTHEAST SUFFOLK J.M.R. BAKER Summary Sightings of amphibians and reptiles were recorded over 3195 km of travel in northeast Suffolk from March to September each year from 2013 to 2020. Two hundred and ninety carcasses were recorded (9 per 100 km), one live common toad and one live grass snake. Amphibian roadkill comprised almost exclusively common toad (n = 202), followed by common frog (n = 6) and great crested newt (n = 2). Slowworm was the most abundant reptile mortality (n = 49), followed by grass snake (n = 30) and adder (n = 1). The numbers of toads peaked with the spring breeding migration, but they were killed on roads throughout the year, with a second, smaller, peak in the autumn. Reptiles were found mostly during the warmer months, probably reflecting higher activity levels during this time. Although reptile carcasses were relatively scarce, they were found at rates comparable to that of the hedgehog, a more familiar roadkill victim. Introduction Roads have a huge, mostly negative, impact on wildlife. For example, negative impacts on birds extend, on average, 700 m from roads, so that in an area with high road density such as Great Britain over 70% of land is affected (Cooke et al., 2020). Among the negative impacts of roads on wildlife (direct mortality, habitat fragmentation, pollution run-off and noise) roadkill is the most immediately apparent. Counts of wildlife killed on roads do not, however, necessarily translate into impacts on populations. In fact roadside habitat can favour some species (e.g. Cooke et al., 2020) so that in such cases high mortality may reflect greater local abundance. Nevertheless, information gained from extensive and systematic monitoring of roadkill can be useful not only in quantifying its magnitude but also in determining population trends, species distribution mapping and studies of behaviour, contaminants and disease (Schwartz et al., 2020). The current observations are primarily concerned with amphibians and reptiles (herpetofauna). These taxa are highly vulnerable to the negative effects of roads (Hels & Buchwald, 2001; Rytwinski & Fahrig, 2012) and impacts on amphibian populations extend as far as 500 m from the road (review in Beebee, 2013). With the exception of the common toad Bufo bufo, which crosses roads in large numbers during its springtime migration, resulting in mortalities concentrated at particular locations (e.g. Gittins, 1983), there is little information on herpetofaunal roadkill in Britain. This may be, at least in part, because amphibians and reptiles are relatively small animals and more easily overlooked than larger vertebrates. Nevertheless, in one of the earliest studies of road mortality, conducted on a two-mile section of the A6003, on the western outskirts of Corby, in 1959 and 1960, Hodson (1966) found that an amphibian, the common frog Rana temporaria was the most frequent non-avian casualty. The only other herpetofauna he recorded was the grass snake Natrix helvetica but at a much lower frequency (one per year). The relative scarcity of reptile roadkill in Britain is probably a further reason for the lack of data for these species. The current study is based on observations made during recreational travel (by Trans. Suffolk Nat. Soc. 56 (2020)


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