Acta Herpetologica 11(2): 227-231, 2016 ISSN 1827-9635 (print) © Firenze University Press ISSN 1827-9643 (online) www.fupress.com/ah DOI: 10.13128/Acta_Herpetol-17922 Heavy traffic, low mortality - tram tracks as terrestrial habitat of newts Mikołaj Kaczmarski*, Jan M. Kaczmarek University of Life Sciences, Institute of Zoology, Wojska Polskiego 71c, 60-625 Poznań, Poland. * Corresponding author. E-mail: traszka. com@gmail.com Submitted on 2016, 3nd February; revised on 2016, 29th April; accepted on 2016, 10th June Editor: Adriana Bellati Abstract. Amphibian mortality caused by rail traffic has not attracted much attention in comparison to road mor- tality. Density of railways in landscape, as well as traffic intensity, is usually much lower than in case of roads. As a consequence, their overall effect on amphibian populations is tacitly assumed to be less negative. To test whether very intensive rail traffic can cause substantial mortality in population of a small amphibian, we investigated a Smooth newt Lissotriton vulgaris population located in the city of Poznań, W Poland, where tram tracks border isolated breed- ing ponds. We performed controls during the peak of autumn migratory activity along the tracks. Less than 1% of all individuals found during the survey were killed by rail traffic. Observed mortality was very low despite large num- ber of individuals present on the track and intensive tram traffic. As negative effects of traffic are low, rail or tram embankments can provide an important terrestrial habitat for small European newts. Keywords. Amphibian, Lissotriton vulgaris, mortality, railway, Smooth newt, traffic. Amphibian mortality caused by rail transport has not attracted much attention in comparison to road mortality, which is investigated by a growing number of papers (Coffin, 2007; Elzanowski et al., 2009; Glis- ta et al., 2009; Cayuela et al., 2015; Franch et al., 2015). Density of railways in landscape, as well as traffic inten- sity, is usually much lower than in case of roads. As a consequence, their overall effect on amphibian popula- tions is tacitly assumed to be less negative. Despite that, amphibians crossing the railway line suffer from mortal- ity by train collisions (Budzik and Budzik, 2013) or tur- bulence effect (Barandun, 1991). Railway infrastructure can block or hinder migration, especially in case of large newts or toads (Etienne et al., 2003). However, the struc- ture of a typical railway track could enable small, crawl- ing amphibians, like European Lissotriton newts, to move under the rails, therefore minimizing the risk of collision. On the other hand, in case of small species, dead indi- viduals are more likely to disappear quickly after death, because of scavenging (Beckmann and Shine, 2014), dry- ing (Budzik and Budzik, 2013) or physical destruction by traffic (Hels and Buchwald, 2001). As a consequence, rail traffic mortality rates for species like Lissotriton newts are likely to be underestimated, just as they are for road traffic (Elzanowski et al., 2009; Cayuela et al., 2015). To verify whether very intensive rail traffic can cause sub- stantial mortality in populations of a small amphibian, we investigated a Smooth newt Lissotriton vulgaris Lin- naeus, 1758 population located in the Poznań city, Poland (52°23’31.1”N, 16°58’33.5”E), where the breeding site is located near double tram tracks with very heavy traf- fic load. Smooth newt is considered the most widespread newt of the Old World (Arntzen et al., 2009; Sparre- boom, 2014). Although L. vulgaris is a common species, detailed analyses show that it undergoes a broad decline in Western Europe, analogous to that of other newt spe- cies (Denoël, 2012; Denoël et al., 2013). It breeds in a vast diversity of water bodies and is generally associated with different kinds of wetlands (Bell, 1977). The breed- ing sites are two small ponds (about 700 m2 and 900 m2, 228 Mikołaj Kaczmarski, Jan M. Kaczmarek respectively) completely overgrown by Phragmites austra- lis (Cav.)  Trin.  ex  Steud,  1841 within an intensively man- aged urban park (Fig. 1). Until 1960s, the studied area was the part of suburban farmland with a small river valley; urban development in 1970-1980s isolated L. vul- garis from surrounding populations. The park borders with housing estates and a forested buffer of an industrial area, containing a fish-inhabited pond that is the breed- ing site for common toads Bufo bufo Linnaeus, 1758. The double tram track is located along the southern border of the park. Daytime traffic load is ca. 20 trams/hour, peak- ing at late evening and early morning hours (over 40 trams/hour). The structure of the tram track is analogous to a typical railway track: wooden sleepers (Fig. 2C) on crushed stone aggregate (Fig. 2A, B). We performed 11 controls between 6th and 19th October 2014 (peak of autumn migratory activity). We searched for newts between 20:00 and 24:00 along the 300-m transect at the edge of the tram tracks in their section closest to the breeding ponds. We also searched for newts crossing pedestrian trails within the park and roads along park boundaries. In total, 303 individuals were noted along tram tracks in the whole survey period. We found individuals of both sexes, as well as juveniles (Table 1). Captured individu- als were measured (SVL, body mass) using digital caliper and electronic scale. However, we did not mark individu- als, so numbers are given separately for each day, with the highest number of animals observed on October 15th (68 individuals; Fig. 3). Only 3 individuals killed by tram were found during the survey period. Dead newts were found only at pedestrian crossings. Newts were observed at the edge of the track as well as between the rails (Fig. 3). No individuals were found elsewhere (forested area, park trails or roads along the park boundaries). It has already been suggested that railway tracks do not necessarily block the migration efforts of newts. No significant genetic effects were found in populations of the Alpine newt Ichtyosaura alpestris Laurenti, 1768 at both sides of the 30-year old railway, which could have been a consequence of newt migration across the track (Prunier et al., 2014). In contrast, in case of North Ameri- can salamander Ambystoma opacum Gravenhorst, 1807 a 100-years old railway led to total genetic isolation of two subpopulations divided by tracks (Bartoszek and Greenwald, 2009). Such difference could be ascribed to the time of isolation or the lesser mobility of Ambystoma opacum compared to European newts. Also, the popula- Fig. 1. Situational map showing the area of the research. 229Tram tracks as terrestrial habitat of newts tion researched by Bartoszek and Greenwald (2009) was already isolated and had relatively low number of indi- viduals, while Prunier et al. (2014) performed analysis on landscape scale with large number of interconnected pop- ulations. Another evidence for low level of isolation pro- vided by railway lines is the work of Budzik and Budzik (2013), who found no dead newts along the 45-km tran- sect along the railway line in SE Poland. Budzik and Budzik (2013) suggested that either newts disappear shortly after death due to their small body size, or they are not subject to mortality caused by rail traffic. Our results provide evidence for the latter hypothesis, as observed mortality was low compared to high number of live speci- mens and great intensity of tram traffic, much exceeding the train traffic intensity in Budzik and Budzik (2013). Dead newts were found only at pedestrian crossings, where newt movement under the tracks is impossible, and animals are forced to move over instead of under the rails. We confirmed that, in late autumn, L. vulgaris from the urban population use the tram track as their terres- trial habitat, and are not subject to extensive mortality. The timing of the controls enabled us to search for dead individuals just after the evening peak of tram traffic (and, presumably, the peak of newt activity and mortal- ity). Temperature and humidity during all controls were likely to prevent the dead individuals from quick drying. As dead individuals were collected during the night, the risk of scavenging by birds was minimal. We could not exclude the possibility of scavenging by mammals (e.g., hedgehogs, feral cats, foxes, rats), but we treat it unlikely as the controls were performed early in the night when tram and human traffic was still relatively intensive, restricting the mammalian activity. Thus, we feel that the detection probability of dead newts was higher than usually assumed for estimating road mortality (Hels and Buchwald, 2001; Elzanowski et al., 2009). Although the length of the transect was short compared to some oth- er studies (e.g., Budzik and Budzik, 2013), we stress that it was enough to cover most of the terrestrial habitat of the investigated population, as the surrounding areas are either build-up or do not provide enough shelter for the newts (Kaczmarek et al., 2014.). Therefore, we suggest that the rail aggregate consisting of sleepers and stones is a crucial winter habitat for the investigated population (Fig. 2). A large number of shelters within rail aggregate, providing humid and prey-rich terrestrial habitat, enable the persistence of a large newt population, despite iso- lation and deteriorating quality of the breeding pond. Additionally, driving trams directly scare away large Fig. 2. (A) Male Smooth newt L. vulgaris during the searching for prey among crushed stone aggregate; (B) crushed stone aggregate as newts habitat with the rail in the background; (C) female Smooth newt found feeding on earthworm on the surface of a wooden sleeper (October, 2014). Table 1. Morphometric values of L. vulgaris from 14th October. x min max SD n SVL [mm] MM 38.78 31.03 45.07 3.17 25 FF 38.82 29.67 46.11 4.36 28 JUV 22.92 19.86 27.45 2.93 7 Body mass [g] MM 1.79 1.18 2.93 0.40 25 FF 1.91 0.72 3.12 0.58 28 JUV 0.32 0.12 0.59 0.16 7 Fig. 3. Number of individuals during each day of our survey with mortality (15th October, one female; 18th October, one male and one juvenile). 230 Mikołaj Kaczmarski, Jan M. Kaczmarek predators, thus reducing predation risk. Easily warming up stone aggregate could also affect newt activity pat- tern, as active individuals were observed until the end of December (pers. comm.). Presence of juvenile individuals (up to 38% in day- samples over 20 individuals) is interesting (Fig. 3). Malmgren (2002) showed that out of the pond move- ment of juvenile newts was more random than of the adult individuals, which is in accordance with theoretical framework presented by Pittman et al. (2014). However, the majority of juveniles in Malmgren (2002) chose simi- lar direction as adults, i.e., towards the forest. Abundance of juvenile individuals on the track sug- gests that their movements are nonrandom. If juvenile newts used ‘normal’ cues, signaling the proximity of opti- mal terrestrial habitat (e.g., humidity gradient, shadow, slope axis), they should move along the old riverbed and remain within the park. Therefore, we suppose that at least some juvenile individuals follow the adults using olfactory cues (Hayward et al., 2000). In contrast to low rail traffic mortality, European newts are vulnerable to road traffic mortality (Denoël, 2012). For slow-moving newts, the probability of being killed is very high regardless of traffic intensity (Hels and Buchwald, 2001). In a setup similar to this study (500- m transect along a local road, breeding newt population migrating from pond located 300 m from the transect), the road  kills-to-spawners ratio for L. vulgaris was higher than for any other amphibian, with more than half of the population killed each year (Elzanowski et al., 2009). In such a context, rail traffic seems much less detrimental for newt populations, despite potential mortality caused by herbicide spraying (Brühl et al., 2013). It seems that in the studied population, where the managed urban green- ery does not provide a sufficient number of high-quality hibernation sites, cavities within the rail aggregate act as the key wintering habitat. It requires further investiga- tion whether the rail/tram aggregate and sleepers are a suitable all-year habitat for juvenile newts. Whereas it is indisputable that roads and railways negatively affect ani- mals, some positive effects on birds and reptiles were also reported (Morelli et al., 2014). We argue that for small, crawling amphibians like L. vulgaris the benefits from new habitats created by railway infrastructure can out- weigh the potential costs of traffic-induced mortality. ACKNOWLEDGEMENTS Animal collection was performed according to RDOS permit no. WPN-II.6401.245.2014.AG. 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