et al. 2015). In some cases, structures that were not originally designed as wildlife
passes have been adapted to better allow animal crossings. For instance, culverts were
modified by the addition of a bench to facilitate wildlife crossing when the culvert is
wet (Iuell et al. 2003). In some cases, the adaptation is as easy as removing the gravel
below pairs of sleepers to create a gap to allow small vertebrates, like spotted turtles
(Clemmys guttata) in the USA, to cross under the sleepers, to where they were
funnelled by a fence (Pelletier et al. 2006). Culverts have been found to be used by
animals to bypass railways in Australia (Hunt et al. 1987) and in Spain (Yanes et al.
1995; Rodríguez et al. 1996, 1997). However, culvert dimensions or the surrounding
habitats influence their use by vertebrates (Hunt et al. 1987; Yanes et al. 1995;
Rodríguez et al. 1996, 1997). For instance, small culverts were used by small mammals, but they were unsuitable for ungulates (Rodríguez et al. 1996) and the addition
of natural vegetation and refuges such as stones increased crossing rates for small
animals (Hunt et al. 1987; Yanes et al. 1995). Not unexpectedly, longer passes have
lower crossing rates for several taxa (Hunt et al. 1987; Yanes et al. 1995).
Notice, however, that all the examples of pass monitoring reported, at the most, the
intensity of crossing, not the functional connectivity—two variables that are not necessarily coupled (Riley et al. 2006). Thus the implementation of these mitigation measures should be complemented with genetic analyses at the population level to assess
whether they contribute to the effective reduction of barrier effects (Riley et al. 2006).
Management Guidelines
In Fig. 4.1 we present in a schematic way the steps to be followed in an “Ideal
Protocol to Mitigate Railway Barrier Effects”. These include:
Forecasting Impacts
To know the wildlife status in the whole region, it is necessary to assess the impact
of potential routes, to understand the target-species ecology, as WTCs are usually
correlated with animal abundance (e.g., D’Amico et al. 2015), and the latter can
temporally and geographically change along the biological cycle (e.g., moose in
Canada or Norway; Child 1983; Gundersen et al. 1998; or sika deer Cervus nippon
in Japan; Ando 2003). Impacts can be predicted by NGS (Balkenhol and Waits
2009) or by censuses (Species Distribution Models, Clauzel et al. 2013). In addition, individual assignment tests and graph theory could be combined in landscape
analyses to identify connectivity zones that should be preserved, and computer
simulations could be run to evaluate population dynamics under several barrier
effect levels (Balkenhol and Waits 2009; Clauzel et al. 2013). Thus, by combining
these approaches, planners will be able to select the alternatives with the lowest
barrier effects on wildlife.
56
R. Barrientos and L. Borda-de-Água
passes have been adapted to better allow animal crossings. For instance, culverts were
modified by the addition of a bench to facilitate wildlife crossing when the culvert is
wet (Iuell et al. 2003). In some cases, the adaptation is as easy as removing the gravel
below pairs of sleepers to create a gap to allow small vertebrates, like spotted turtles
(Clemmys guttata) in the USA, to cross under the sleepers, to where they were
funnelled by a fence (Pelletier et al. 2006). Culverts have been found to be used by
animals to bypass railways in Australia (Hunt et al. 1987) and in Spain (Yanes et al.
1995; Rodríguez et al. 1996, 1997). However, culvert dimensions or the surrounding
habitats influence their use by vertebrates (Hunt et al. 1987; Yanes et al. 1995;
Rodríguez et al. 1996, 1997). For instance, small culverts were used by small mammals, but they were unsuitable for ungulates (Rodríguez et al. 1996) and the addition
of natural vegetation and refuges such as stones increased crossing rates for small
animals (Hunt et al. 1987; Yanes et al. 1995). Not unexpectedly, longer passes have
lower crossing rates for several taxa (Hunt et al. 1987; Yanes et al. 1995).
Notice, however, that all the examples of pass monitoring reported, at the most, the
intensity of crossing, not the functional connectivity—two variables that are not necessarily coupled (Riley et al. 2006). Thus the implementation of these mitigation measures should be complemented with genetic analyses at the population level to assess
whether they contribute to the effective reduction of barrier effects (Riley et al. 2006).
Management Guidelines
In Fig. 4.1 we present in a schematic way the steps to be followed in an “Ideal
Protocol to Mitigate Railway Barrier Effects”. These include:
Forecasting Impacts
To know the wildlife status in the whole region, it is necessary to assess the impact
of potential routes, to understand the target-species ecology, as WTCs are usually
correlated with animal abundance (e.g., D’Amico et al. 2015), and the latter can
temporally and geographically change along the biological cycle (e.g., moose in
Canada or Norway; Child 1983; Gundersen et al. 1998; or sika deer Cervus nippon
in Japan; Ando 2003). Impacts can be predicted by NGS (Balkenhol and Waits
2009) or by censuses (Species Distribution Models, Clauzel et al. 2013). In addition, individual assignment tests and graph theory could be combined in landscape
analyses to identify connectivity zones that should be preserved, and computer
simulations could be run to evaluate population dynamics under several barrier
effect levels (Balkenhol and Waits 2009; Clauzel et al. 2013). Thus, by combining
these approaches, planners will be able to select the alternatives with the lowest
barrier effects on wildlife.
56
R. Barrientos and L. Borda-de-Água