Hels and Buchwald 2001; Carvalho and Mira 2011), records for railways are much
rarer (van der Grift and Kuijsters 1998). Unfortunately, there are no studies that
compare detectability and persistence rates of carcasses between road and railway
surveys, so the difference in numbers remains an open question.
Considering only the studies that aimed to survey train casualties of all species,
the frequency of amphibians can reach up to 47% of all vertebrate records (Heske
2015), while the records of reptiles represent ca. 4% (Spain) and 6% (USA) of
carcasses (Heske 2015; SCV 1996). In Netherlands, for example, no carcasses of
amphibians or reptiles were ever found (van der Grift and Kuijsters 1998), while in
Spain, only reptiles were recorded (SCV 1996).
In Chicago state, USA, amphibians were the most abundant taxonomic group
recorded in train collisions (Heske 2015), mainly northern leopard frogs (Lithobates
pipiens) and American toads (Bufo americanus), common species in the region.
Mortalities of amphibians were particularly high after rain events, when these species are most active and are also frequently found dead on the roads (Heske 2015).
Budzic and Budzic (2014) conducted a survey specifically aimed to estimate
amphibian mortality on 34 km of Polish railways. They found that three species
were most affected by train accidents: the common toad (Bufo bufo), the common
frog (Rana temporaria) and the green frog (Pelophylax kl. esculentus), and most of
dead individuals (77%) were adult common toads. Although mortality rates can be
high, all three species are considered common in Europe. In fact, two of the species
affected by railway mortality (common toad and common frog), are among the most
common European amphibians, for which there is also evidence of high
road-mortality (Hels and Buchwald 2001; Matos et al. 2012; Orłowski 2007).
As in roads, the spring migration (or autumn migration, in some regions) seems
to be the period of highest amphibian mortality on railway tracks, as 87% of all
accidents occurred in that season (Budzic and Budzic 2014). Yet, railway mortality
of amphibians seems to depend on animals’ physical features (such as body size
and limb length) and should be associated with the agility of the species (Budzic
and Budzic 2014). While in the case of roads, the velocity of individuals is used as
a proxy for agility (Hels and Buchwald 2001), in the case of railway tracks, agility
relates mainly to the ability to overcome obstacles (Budzic and Budzic 2014; SCV
1996). Due to its physical features, the common toad was more likely to become
trapped between rails, indicating that this species (and others with similar physical
features) may be more vulnerable to railway mortality (Budzic and Budzic 2014).
Some species of small size may be less vulnerable because they cannot cross the rail
track (Heske 2015). However, they may be affected by railways at the level of gene
flow due to barrier effects (Holderegger and Di Giulio 2010), which may be also a
conservation problem.
Concerning reptile mortality, 13 snakes (4%) were recorded across the whole
Spanish railway network between 1990 and 1995. Only two species were identified:
the ladder snake (Elaphe scalaris) and the Montpellier snake (Malpolon monspessulanus), both common reptiles in the country (SCV 1996).
The railway bed may be lethal itself for smaller animals that can become trapped
between the rails, where they may be susceptible to predation or physiological
18
S.M. Santos et al.
rarer (van der Grift and Kuijsters 1998). Unfortunately, there are no studies that
compare detectability and persistence rates of carcasses between road and railway
surveys, so the difference in numbers remains an open question.
Considering only the studies that aimed to survey train casualties of all species,
the frequency of amphibians can reach up to 47% of all vertebrate records (Heske
2015), while the records of reptiles represent ca. 4% (Spain) and 6% (USA) of
carcasses (Heske 2015; SCV 1996). In Netherlands, for example, no carcasses of
amphibians or reptiles were ever found (van der Grift and Kuijsters 1998), while in
Spain, only reptiles were recorded (SCV 1996).
In Chicago state, USA, amphibians were the most abundant taxonomic group
recorded in train collisions (Heske 2015), mainly northern leopard frogs (Lithobates
pipiens) and American toads (Bufo americanus), common species in the region.
Mortalities of amphibians were particularly high after rain events, when these species are most active and are also frequently found dead on the roads (Heske 2015).
Budzic and Budzic (2014) conducted a survey specifically aimed to estimate
amphibian mortality on 34 km of Polish railways. They found that three species
were most affected by train accidents: the common toad (Bufo bufo), the common
frog (Rana temporaria) and the green frog (Pelophylax kl. esculentus), and most of
dead individuals (77%) were adult common toads. Although mortality rates can be
high, all three species are considered common in Europe. In fact, two of the species
affected by railway mortality (common toad and common frog), are among the most
common European amphibians, for which there is also evidence of high
road-mortality (Hels and Buchwald 2001; Matos et al. 2012; Orłowski 2007).
As in roads, the spring migration (or autumn migration, in some regions) seems
to be the period of highest amphibian mortality on railway tracks, as 87% of all
accidents occurred in that season (Budzic and Budzic 2014). Yet, railway mortality
of amphibians seems to depend on animals’ physical features (such as body size
and limb length) and should be associated with the agility of the species (Budzic
and Budzic 2014). While in the case of roads, the velocity of individuals is used as
a proxy for agility (Hels and Buchwald 2001), in the case of railway tracks, agility
relates mainly to the ability to overcome obstacles (Budzic and Budzic 2014; SCV
1996). Due to its physical features, the common toad was more likely to become
trapped between rails, indicating that this species (and others with similar physical
features) may be more vulnerable to railway mortality (Budzic and Budzic 2014).
Some species of small size may be less vulnerable because they cannot cross the rail
track (Heske 2015). However, they may be affected by railways at the level of gene
flow due to barrier effects (Holderegger and Di Giulio 2010), which may be also a
conservation problem.
Concerning reptile mortality, 13 snakes (4%) were recorded across the whole
Spanish railway network between 1990 and 1995. Only two species were identified:
the ladder snake (Elaphe scalaris) and the Montpellier snake (Malpolon monspessulanus), both common reptiles in the country (SCV 1996).
The railway bed may be lethal itself for smaller animals that can become trapped
between the rails, where they may be susceptible to predation or physiological
18
S.M. Santos et al.