stress. This is the case of railway-induced mortality of Eastern box turtles
(Terrapene carolina), in the USA, that often cannot escape when trapped between
railway tracks. In a controlled experiment with 12 turtles, Kornilev et al. (2006)
showed that most turtles clearly have the ability to escape at railway crossings,
although mortality rates within the railway were still high. Notice, as well, that
when between railway tracks, turtles can quickly reach critically high body temperatures, even on relatively mild days (Kornilev et al. 2006).
How Different Is Mortality in Railways and Roads?
Only a few studies have directly compared railway and road mortality, a comparison
that is not easy because railway impacts are more difficult to detect (SCV 1996).
Considering the diversity of taxonomic groups that are frequently killed on railways,
it may be surprising that trains can cause such high mortality among some species
(see ungulates, for example), because, compared to cars, trains are often less frequent, noisier, larger and, most of the times, travel at low to medium speeds (Heske
2015; Morelli et al. 2014). However, even freight trains can sometimes reach speeds
close to 200 km/h and cannot stop quickly when encountering animals on the rails.
This obviously leads to high mortality numbers on railways that could be avoided
more easily on roads (Dorsey et al. 2015; Heske 2015). Accordingly, the number of
dead bears and moose along railways often exceed death rates along roads (Belant
1995; Boscagli 1987; Modafferi and Becker 1997; Waller and Servheen 2005). On
the other hand, for other species the railways may lead to lower mortality. For
instance, the vibrations of approaching trains can be felt along the rails and this may
give warning to some terrestrial vertebrates. This seems to be the case of snakes that
may be warned of approaching trains by vibrations transmitted through the rails or
the ballast (Heske 2015). In addition, while the traffic on roads can be simultaneously
two-way, trains approach from one direction at a time, and the width of a road is
greater than the width of a railway, decreasing the vulnerability of vertebrates that
cross railways (Heske 2015). In a study that compared mortality rates between roads
and railways, it was found that railways had notably lower mortalities of songbirds,
small mammals, and turtles when compared to those of roads (Heske 2015), suggesting that diurnal and vagile species may be more efficient at avoiding trains than
avoiding cars and trucks on busy two-way roads (Heske 2015).
Future Directions
In Spain, estimates of vertebrate mortality due to train collisions averages
36.5 vertebrates/km/year (not including high speed trains; SCV 1996). In
high-speed railways, this estimate grows to, at least, 92 vertebrates/km/year (SCV
1996). Nevertheless, in general, most of the species recorded as train casualties are
2 Current Knowledge on Wildlife Mortality in Railways
19
(Terrapene carolina), in the USA, that often cannot escape when trapped between
railway tracks. In a controlled experiment with 12 turtles, Kornilev et al. (2006)
showed that most turtles clearly have the ability to escape at railway crossings,
although mortality rates within the railway were still high. Notice, as well, that
when between railway tracks, turtles can quickly reach critically high body temperatures, even on relatively mild days (Kornilev et al. 2006).
How Different Is Mortality in Railways and Roads?
Only a few studies have directly compared railway and road mortality, a comparison
that is not easy because railway impacts are more difficult to detect (SCV 1996).
Considering the diversity of taxonomic groups that are frequently killed on railways,
it may be surprising that trains can cause such high mortality among some species
(see ungulates, for example), because, compared to cars, trains are often less frequent, noisier, larger and, most of the times, travel at low to medium speeds (Heske
2015; Morelli et al. 2014). However, even freight trains can sometimes reach speeds
close to 200 km/h and cannot stop quickly when encountering animals on the rails.
This obviously leads to high mortality numbers on railways that could be avoided
more easily on roads (Dorsey et al. 2015; Heske 2015). Accordingly, the number of
dead bears and moose along railways often exceed death rates along roads (Belant
1995; Boscagli 1987; Modafferi and Becker 1997; Waller and Servheen 2005). On
the other hand, for other species the railways may lead to lower mortality. For
instance, the vibrations of approaching trains can be felt along the rails and this may
give warning to some terrestrial vertebrates. This seems to be the case of snakes that
may be warned of approaching trains by vibrations transmitted through the rails or
the ballast (Heske 2015). In addition, while the traffic on roads can be simultaneously
two-way, trains approach from one direction at a time, and the width of a road is
greater than the width of a railway, decreasing the vulnerability of vertebrates that
cross railways (Heske 2015). In a study that compared mortality rates between roads
and railways, it was found that railways had notably lower mortalities of songbirds,
small mammals, and turtles when compared to those of roads (Heske 2015), suggesting that diurnal and vagile species may be more efficient at avoiding trains than
avoiding cars and trucks on busy two-way roads (Heske 2015).
Future Directions
In Spain, estimates of vertebrate mortality due to train collisions averages
36.5 vertebrates/km/year (not including high speed trains; SCV 1996). In
high-speed railways, this estimate grows to, at least, 92 vertebrates/km/year (SCV
1996). Nevertheless, in general, most of the species recorded as train casualties are
2 Current Knowledge on Wildlife Mortality in Railways
19