Data Collection
We collected data on elephant casualties due to collisions with trains between 1974
and 2015, using records maintained by the Government of West Bengal (2012), the
Alipurduar Divisional Railway Manager’s office, several offices of the West Bengal
Forest Department, tea association offices, scientific reports and publications (Roy
et al. 2009; Dasgupta and Ghosh 2015), and newspaper reports. These records
include date, time, location, number of animals injured or killed, and the gender and
age groups of these animals. We also collected first-hand information on some of the
more recent accidents during our field research on elephant ecology in this region.
To estimate the distribution and relative abundance of elephants, we conducted
surveys along this railway track during three seasons in 2015: non-crop (Jan–Mar),
maize cultivation/harvest (Apr–Jul), and paddy cultivation/harvest (Aug–Dec). The
survey was done along a 150 km stretch of the 161-km railway track, excluding a
part of the Siliguri Junction–Gulma station and Rajabhatkhawa station–Alipurduar
junction, as these portions fall within human habitation areas with no elephant
presence. The surveys were conducted along the track on foot by a team consisting
of one researcher and two assistants, aiming to detect elephant signs (dung, tracks,
footprints, feeding signs), as well as direct sightings, on both sides of the track, up
to a distance of 10 m. Every sign was counted separately and thus footprints, dung,
and tracks at a particular location were counted as three separate pieces of evidence,
as in general it was not possible to determine whether these signs, most of which
were old, came from the same elephant or different ones. The paddy season survey
also included the mapping of elephant corridors, which mostly pass through tea
gardens in this region. All the evidence of elephant evidence that we detected were
GPS-referenced and plotted on Arc GIS 10.3.1. (ESRI 2014). The non-crop season
survey took 33 days, the maize season survey 22 days, and the paddy season
survey 41 days to complete.
Data Analysis
Using data on the spatial distribution of elephant signs (dung, footprints, track
signs, feeding signs), we generated a “susceptibility map” to estimate the locations
along the railway track where accidents were more likely to occur due to the
concentration of elephant activity. This map was computed using the point density
tool of Arc GIS 10.3.1 software, and the GPS locations of elephant signs. The point
density tool calculates the density of point features around a given neighborhood of
each raster cell by dividing the number of points that fall in the neighborhood by the
area of the neighborhood. In our computations, we used an output cell size of
0.001375 km
2 and search radius of 0.11458 km, based on values provided automatically by the GIS software. We also generated a “kernel density map” in
ARC GIS 10.3.1, taking into account all indirect evidence of elephants (dung,
10 Railways and Wildlife: A Case Study …
161
We collected data on elephant casualties due to collisions with trains between 1974
and 2015, using records maintained by the Government of West Bengal (2012), the
Alipurduar Divisional Railway Manager’s office, several offices of the West Bengal
Forest Department, tea association offices, scientific reports and publications (Roy
et al. 2009; Dasgupta and Ghosh 2015), and newspaper reports. These records
include date, time, location, number of animals injured or killed, and the gender and
age groups of these animals. We also collected first-hand information on some of the
more recent accidents during our field research on elephant ecology in this region.
To estimate the distribution and relative abundance of elephants, we conducted
surveys along this railway track during three seasons in 2015: non-crop (Jan–Mar),
maize cultivation/harvest (Apr–Jul), and paddy cultivation/harvest (Aug–Dec). The
survey was done along a 150 km stretch of the 161-km railway track, excluding a
part of the Siliguri Junction–Gulma station and Rajabhatkhawa station–Alipurduar
junction, as these portions fall within human habitation areas with no elephant
presence. The surveys were conducted along the track on foot by a team consisting
of one researcher and two assistants, aiming to detect elephant signs (dung, tracks,
footprints, feeding signs), as well as direct sightings, on both sides of the track, up
to a distance of 10 m. Every sign was counted separately and thus footprints, dung,
and tracks at a particular location were counted as three separate pieces of evidence,
as in general it was not possible to determine whether these signs, most of which
were old, came from the same elephant or different ones. The paddy season survey
also included the mapping of elephant corridors, which mostly pass through tea
gardens in this region. All the evidence of elephant evidence that we detected were
GPS-referenced and plotted on Arc GIS 10.3.1. (ESRI 2014). The non-crop season
survey took 33 days, the maize season survey 22 days, and the paddy season
survey 41 days to complete.
Data Analysis
Using data on the spatial distribution of elephant signs (dung, footprints, track
signs, feeding signs), we generated a “susceptibility map” to estimate the locations
along the railway track where accidents were more likely to occur due to the
concentration of elephant activity. This map was computed using the point density
tool of Arc GIS 10.3.1 software, and the GPS locations of elephant signs. The point
density tool calculates the density of point features around a given neighborhood of
each raster cell by dividing the number of points that fall in the neighborhood by the
area of the neighborhood. In our computations, we used an output cell size of
0.001375 km
2 and search radius of 0.11458 km, based on values provided automatically by the GIS software. We also generated a “kernel density map” in
ARC GIS 10.3.1, taking into account all indirect evidence of elephants (dung,
10 Railways and Wildlife: A Case Study …
161