inhabit grassland and semi-desert areas and sometimes form large herds of several
thousand animals. Under severe climate conditions, the estimated lifespan in the
wild is 7–8 years (Batsaikhan et al. 2010). The rutting period is in winter, and
females over 2 years old usually give birth to one calf in late June or early July
(Lhagvasuren and Milner-Gulland 1997). The long-distance movements of this
species for migration or nomadism were already understood before scientific
tracking started (Jiang et al. 1998; Lhagvasuren and Milner-Gulland 1997). Since
then, analyses of gazelle movements in relation to habitat selection and environmental factors, including the presence of a railway, have brought many new findings on the ecology of this species and related conservation issues.
Using modern technology, we have been able to prove the capability of the
Mongolian gazelle to travel long distances. For instance, Argos systems and GPS
with satellite communication systems have been used to track wild ungulates in
Mongolia (Kaczensky et al. 2010). We showed that Mongolian gazelles moved
distances greater than 300 km (the maximum linear distance between two locations
traveled by one individual gazelle in a year) and changed their range seasonally (Ito
et al. 2006, 2013b). The gazelles moved more than 100 km per week during some
periods of the year, whereas the distances moved were short in other periods.
Interannual differences in the seasonal range locations among the same individuals
were also observed, which in some cases were larger than 300 km in winter,
suggesting nomadic movements rather than typical seasonal migrations between
specific locations (Ito et al. 2013b; Olson et al. 2010).
Understanding why and how animals move long distances is important both for
purely scientific purposes and for conservation. Studies on this topic have shown that
environmental factors play a pivotal role, and the normalized-difference vegetation
index (NDVI) has mainly been used as an index of the amount of live plants in
studies of the Mongolian gazelle. For instance, Leimgruber et al. (2001) showed that
the winter and the calving grounds in the eastern steppes of Mongolia (identified
based on expert knowledge of scientists and pastoralists, but not tracking data), had
the highest NDVI scores during periods when gazelles used these areas. In a study
comparing gazelle distribution and NDVI values in different seasons in the eastern
steppes, Mueller et al. (2008) showed that gazelles preferred areas with intermediate
NDVI values in the spring and autumn. Similarly, during a drought period in
September 2005, Olson et al. (2009a) reported a mega-herd of more than 200,000
gazelles in areas with a high probability of gazelle occurrence predicted by a
NDVI-based model. In the southeastern Gobi, the shifts in NDVI values between the
summer and winter ranges explained the gazelles’ seasonal movements (Ito et al.
2006), and interannual differences in the spatial distribution of NDVI explained the
interannual differences in the seasonal range of the tracked gazelles (Ito et al. 2013b).
The interannual differences in locations were much larger in winter than in summer,
likely because of the large differences in the spatial distribution of snow cover.
Avoidance of areas with deep snow cover by Mongolian gazelles was also reported
in Inner Mongolia, China (Luo et al. 2014). In addition, regional differences in the
amount of vegetation across the species’ spatial distribution also led to intraspecific
variations of their movement patterns (Imai et al. 2017).
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thousand animals. Under severe climate conditions, the estimated lifespan in the
wild is 7–8 years (Batsaikhan et al. 2010). The rutting period is in winter, and
females over 2 years old usually give birth to one calf in late June or early July
(Lhagvasuren and Milner-Gulland 1997). The long-distance movements of this
species for migration or nomadism were already understood before scientific
tracking started (Jiang et al. 1998; Lhagvasuren and Milner-Gulland 1997). Since
then, analyses of gazelle movements in relation to habitat selection and environmental factors, including the presence of a railway, have brought many new findings on the ecology of this species and related conservation issues.
Using modern technology, we have been able to prove the capability of the
Mongolian gazelle to travel long distances. For instance, Argos systems and GPS
with satellite communication systems have been used to track wild ungulates in
Mongolia (Kaczensky et al. 2010). We showed that Mongolian gazelles moved
distances greater than 300 km (the maximum linear distance between two locations
traveled by one individual gazelle in a year) and changed their range seasonally (Ito
et al. 2006, 2013b). The gazelles moved more than 100 km per week during some
periods of the year, whereas the distances moved were short in other periods.
Interannual differences in the seasonal range locations among the same individuals
were also observed, which in some cases were larger than 300 km in winter,
suggesting nomadic movements rather than typical seasonal migrations between
specific locations (Ito et al. 2013b; Olson et al. 2010).
Understanding why and how animals move long distances is important both for
purely scientific purposes and for conservation. Studies on this topic have shown that
environmental factors play a pivotal role, and the normalized-difference vegetation
index (NDVI) has mainly been used as an index of the amount of live plants in
studies of the Mongolian gazelle. For instance, Leimgruber et al. (2001) showed that
the winter and the calving grounds in the eastern steppes of Mongolia (identified
based on expert knowledge of scientists and pastoralists, but not tracking data), had
the highest NDVI scores during periods when gazelles used these areas. In a study
comparing gazelle distribution and NDVI values in different seasons in the eastern
steppes, Mueller et al. (2008) showed that gazelles preferred areas with intermediate
NDVI values in the spring and autumn. Similarly, during a drought period in
September 2005, Olson et al. (2009a) reported a mega-herd of more than 200,000
gazelles in areas with a high probability of gazelle occurrence predicted by a
NDVI-based model. In the southeastern Gobi, the shifts in NDVI values between the
summer and winter ranges explained the gazelles’ seasonal movements (Ito et al.
2006), and interannual differences in the spatial distribution of NDVI explained the
interannual differences in the seasonal range of the tracked gazelles (Ito et al. 2013b).
The interannual differences in locations were much larger in winter than in summer,
likely because of the large differences in the spatial distribution of snow cover.
Avoidance of areas with deep snow cover by Mongolian gazelles was also reported
in Inner Mongolia, China (Luo et al. 2014). In addition, regional differences in the
amount of vegetation across the species’ spatial distribution also led to intraspecific
variations of their movement patterns (Imai et al. 2017).
14 Habitat Fragmentation by Railways as a Barrier to Great …
233