trapping and indirect evidence, such as scat identification, was used in Australia
for the first time by Hunt et al. (1987). This technique has been repeatedly
improved, as it was the first widely used method to confirm culvert/wildlife pass
usage. Due to its low costs, it is more cost-effective for short-term surveys than
modern alternatives, like video-surveillance (Ford et al. 2009; Mateus et al. 2011).
However, the use of track pads is limited to optimal conditions, as the material
employed can become useless by rain or livestock passage (Rodríguez et al. 1996,
1997; Mateus et al. 2011), and there can be track misidentification and underestimation of crossings due to track overlapping (Ford et al. 2009). Tracks in
snowy landscapes can help to estimate the qualitative crossing of certain sections
(Olsson et al. 2010), although limitations of this method regarding misidentification and track overlapping are similar to those from sandy beds.
(3) Video-surveillance. Modern technology allows the monitoring of pass usage
thanks to cameras activated by infrared motion detectors at the pass entrance
(Ford et al. 2009; Mateus et al. 2011). This method is constrained by the sensitiveness of the camera monitor sensor (Ford et al. 2009), which is especially
limiting in large passes and with small animals (Mateus et al. 2011), because
video cameras cover small areas and only animals close to the sensor are
recorded (Ford et al. 2009; García-Sánchez et al. 2010; Mateus et al. 2011).
Thus, a logical next step to evaluate the use of wildlife passes has been the
development of wireless sensor networks (García-Sánchez et al. 2010). These
are low-cost devices that, by using a camera at the entrance of the pass and an
infrared motion sensor network deployed in the surrounding area, enable the
recording of reactions of animals approaching the wildlife pass and their
eventual crossings (García-Sánchez et al. 2010).
(4) Capture-mark-recapture (hereinafter “CMR”). These are fine-scale methods as
they are individual-based, but they are intrusive, time- and budget-consuming, and
require safety measures both for the animals and the researchers working around
the transport infrastructures; all this leads to small- to modest-sized samples
(Simmons et al. 2010). Tagging must be adapted to the size and the ecology of the
target species. CMR with numbered plastic tags allowed Bhattacharya et al. (2003)
to monitor bumblebee movement across a railway, with a recapture rate of 31%
(n = 367). In France, Vandevelde et al. (2012) (see Chap. 16) used a thin-point
permanent pen to mark gatekeeper butterflies with a recapture rate of 30%
(n = 149). Alternatively, passive integrated transponders have been proven to be
useful to monitor wildlife passages. Once the animal crosses, an antenna connected
to a decoder unit installed in the pass records the individual, time, and date of
crossing (recapture rate = 50%, n = 6; Soanes et al. 2013).
Radio-tracking-based projects share some of the advantages (fine-scale,
individual-based) and disadvantages (intrusive, time- and budget-consuming) of the
previous methods, although the increasing effectiveness (e.g., satellite-based
telemetry) and decreasing price currently make radio-tracking suitable for a wide
variety of organisms (Simmons et al. 2010). Furthermore, the devices are becoming
miniaturized to the point of being a feasible alternative for some invertebrates (e.g.,
50
R. Barrientos and L. Borda-de-Água
for the first time by Hunt et al. (1987). This technique has been repeatedly
improved, as it was the first widely used method to confirm culvert/wildlife pass
usage. Due to its low costs, it is more cost-effective for short-term surveys than
modern alternatives, like video-surveillance (Ford et al. 2009; Mateus et al. 2011).
However, the use of track pads is limited to optimal conditions, as the material
employed can become useless by rain or livestock passage (Rodríguez et al. 1996,
1997; Mateus et al. 2011), and there can be track misidentification and underestimation of crossings due to track overlapping (Ford et al. 2009). Tracks in
snowy landscapes can help to estimate the qualitative crossing of certain sections
(Olsson et al. 2010), although limitations of this method regarding misidentification and track overlapping are similar to those from sandy beds.
(3) Video-surveillance. Modern technology allows the monitoring of pass usage
thanks to cameras activated by infrared motion detectors at the pass entrance
(Ford et al. 2009; Mateus et al. 2011). This method is constrained by the sensitiveness of the camera monitor sensor (Ford et al. 2009), which is especially
limiting in large passes and with small animals (Mateus et al. 2011), because
video cameras cover small areas and only animals close to the sensor are
recorded (Ford et al. 2009; García-Sánchez et al. 2010; Mateus et al. 2011).
Thus, a logical next step to evaluate the use of wildlife passes has been the
development of wireless sensor networks (García-Sánchez et al. 2010). These
are low-cost devices that, by using a camera at the entrance of the pass and an
infrared motion sensor network deployed in the surrounding area, enable the
recording of reactions of animals approaching the wildlife pass and their
eventual crossings (García-Sánchez et al. 2010).
(4) Capture-mark-recapture (hereinafter “CMR”). These are fine-scale methods as
they are individual-based, but they are intrusive, time- and budget-consuming, and
require safety measures both for the animals and the researchers working around
the transport infrastructures; all this leads to small- to modest-sized samples
(Simmons et al. 2010). Tagging must be adapted to the size and the ecology of the
target species. CMR with numbered plastic tags allowed Bhattacharya et al. (2003)
to monitor bumblebee movement across a railway, with a recapture rate of 31%
(n = 367). In France, Vandevelde et al. (2012) (see Chap. 16) used a thin-point
permanent pen to mark gatekeeper butterflies with a recapture rate of 30%
(n = 149). Alternatively, passive integrated transponders have been proven to be
useful to monitor wildlife passages. Once the animal crosses, an antenna connected
to a decoder unit installed in the pass records the individual, time, and date of
crossing (recapture rate = 50%, n = 6; Soanes et al. 2013).
Radio-tracking-based projects share some of the advantages (fine-scale,
individual-based) and disadvantages (intrusive, time- and budget-consuming) of the
previous methods, although the increasing effectiveness (e.g., satellite-based
telemetry) and decreasing price currently make radio-tracking suitable for a wide
variety of organisms (Simmons et al. 2010). Furthermore, the devices are becoming
miniaturized to the point of being a feasible alternative for some invertebrates (e.g.,
50
R. Barrientos and L. Borda-de-Água