to react and escape in a natural way. The proportion of wildlife escaping from the
tracks was higher, and individuals reacted faster, when the device was switched on
and, importantly, animals did not show evidence of habituation to the warning
signals (Babińska-Werka et al. 2015).
Planting trees (Tremblay and St. Clair 2009) or erecting pole barriers
(Zuberogoitia et al. 2015) in the railway corridor can reduce the WTCs of flying
animals. However, trees could attract animals as well, for perching or feeding, so
pole barriers are preferred since they have fewer side effects. An experiment with
medium- to large-sized birds in Spain showed that most birds shifted or raised the
flight when approaching the pole barrier (Zuberogoitia et al. 2015).
Habitat Management
Vegetation mowing at railway verges was successfully applied to reduce moose
WTCs in Norway, and it could have had three complementary benefits: first,
reducing the attractiveness of the verges for animals, therefore reducing foraging
close to railways (Jaren et al. 1991; Andreassen et al. 2005); second, reducing the
time spent by animals close to the railway, as they could perceive the clearing as
dangerous (Jaren et al. 1991); and, third, allow them ‘see and be seen’ rule, as
provided for both the train driver and the animal, with a greater amount of time to
react to each other and avoid a collision (Jaren et al. 1991). This technique reduced
the number of moose WTCs by half (Jaren et al. 1991; Andreassen et al. 2005). On
the contrary, Eriksson (2014) originally hypothesized that tree-clearing could be the
factor behind the increase in moose and roe deer train collisions in Sweden, as early
successional stages created after mowing provided attractive foraging opportunities
for ungulates, but she found that it had no effect on the increase of WTCs in her
“Before-After-Control-Impact”, the so-called BACI design (Eriksson 2014).
Finally, it is worth mentioning that vegetation removal may increase barrier effects
for small vertebrates, as these do not cross open spaces due to their associated high
predation risks (Hunt et al. 1987; Yanes et al. 1995).
Crossing Structures
Animals use both non-wildlife passes (i.e., those placed and designed for purposes
other than to allow wildlife crossing, like drainage culverts), or wildlife passes
specifically designed on the basis of the target species traits (small tunnels for
amphibians or small mammals; underpasses, overpasses, ecoducts or green bridges
for large mammals) (Smith et al. 2015). Large passes mimicking natural habitat are
more expensive, but they are also the most effective technique for reducing barrier
effects, commonly suitable for most species, including the most demanding ones, like
large carnivores and ungulates (Iuell et al. 2003; Clevenger and Waltho 2005; Smith
4 Railways as Barriers for Wildlife: Current Knowledge
55
tracks was higher, and individuals reacted faster, when the device was switched on
and, importantly, animals did not show evidence of habituation to the warning
signals (Babińska-Werka et al. 2015).
Planting trees (Tremblay and St. Clair 2009) or erecting pole barriers
(Zuberogoitia et al. 2015) in the railway corridor can reduce the WTCs of flying
animals. However, trees could attract animals as well, for perching or feeding, so
pole barriers are preferred since they have fewer side effects. An experiment with
medium- to large-sized birds in Spain showed that most birds shifted or raised the
flight when approaching the pole barrier (Zuberogoitia et al. 2015).
Habitat Management
Vegetation mowing at railway verges was successfully applied to reduce moose
WTCs in Norway, and it could have had three complementary benefits: first,
reducing the attractiveness of the verges for animals, therefore reducing foraging
close to railways (Jaren et al. 1991; Andreassen et al. 2005); second, reducing the
time spent by animals close to the railway, as they could perceive the clearing as
dangerous (Jaren et al. 1991); and, third, allow them ‘see and be seen’ rule, as
provided for both the train driver and the animal, with a greater amount of time to
react to each other and avoid a collision (Jaren et al. 1991). This technique reduced
the number of moose WTCs by half (Jaren et al. 1991; Andreassen et al. 2005). On
the contrary, Eriksson (2014) originally hypothesized that tree-clearing could be the
factor behind the increase in moose and roe deer train collisions in Sweden, as early
successional stages created after mowing provided attractive foraging opportunities
for ungulates, but she found that it had no effect on the increase of WTCs in her
“Before-After-Control-Impact”, the so-called BACI design (Eriksson 2014).
Finally, it is worth mentioning that vegetation removal may increase barrier effects
for small vertebrates, as these do not cross open spaces due to their associated high
predation risks (Hunt et al. 1987; Yanes et al. 1995).
Crossing Structures
Animals use both non-wildlife passes (i.e., those placed and designed for purposes
other than to allow wildlife crossing, like drainage culverts), or wildlife passes
specifically designed on the basis of the target species traits (small tunnels for
amphibians or small mammals; underpasses, overpasses, ecoducts or green bridges
for large mammals) (Smith et al. 2015). Large passes mimicking natural habitat are
more expensive, but they are also the most effective technique for reducing barrier
effects, commonly suitable for most species, including the most demanding ones, like
large carnivores and ungulates (Iuell et al. 2003; Clevenger and Waltho 2005; Smith
4 Railways as Barriers for Wildlife: Current Knowledge
55