225
extinction because of their low densities (relative to other mammals, including their
prey species) and relatively low recruitment rates (where few animals raise offspring that survive to join the breeding population) (Kerley et al. 2003). Tigers also
require large undisturbed landscapes with ample prey to raise young and maintain
long term genetic and demographic viability (Seidensticker and McDougal 1993;
Karanth and Sunquist 1995; Carbone et al. 1999; Jhala et al. 2008). However, such
areas are contracting or becoming increasingly fragmented because of high anthropogenic pressures on natural resources. Whilst India has the world’s largest population of wild tigers, it has also suffered the highest range contraction for the species.
Poaching is mainly for the supply of organs, bones and hides that are smuggled for
use in traditional medicine, mainly into China and south-east Asia (Gratwicke et al.
2008; Nowell 2009).
Efforts to save the tiger started rather late. For example, Project Tiger was initiated in India in 1973 (GOI 2005). However, the strategies used were not time-tested
and were also often weak on scientific rigor, partly because of a general lack of
baseline information on tiger distributions (ibid). Conservation strategies for tigers
had previously focused only on protecting the species in pristine wilderness areas
and were based on the premise that estimates of tiger densities derived from signbased indices (e.g., pugmark census techniques) were adequate to provide information on the survival status of the species. However, detecting tigers through
traditional field survey methods is a challenging task. Tigers require sufficient numbers of large-bodied prey and therefore roam across large that may exceed 100s of
kilometres. They also occur in low densities and often as lone individuals, particularly in closed forests (Gittleman and Harvey 1982; Carbone et al. 2001), are cryptic
by nature and are rarely seen. As a consequence, records relating to tiger distributions and their use of habitats have been inadequate and this has severely impeded
the formulation and implementation of appropriate conservation measures (Blake
and Hedges 2004; Sanderson et al. 2006).
For these reasons, there has been an increasing and now urgent need to devise
rapid yet rigorous population analysis and viability methods with spatial and temporal observations that are repeatable across the varied landscapes that tigers occupy
(Linkie et al. 2006). It is also widely accepted that a landscape approach to tiger
conservation that takes into account the distribution and condition of habitat also
fares better than those that focus only on protecting the species. Although breeding
populations are currently found in eight Asian range states, there are few regular
empirical studies to indicate trends on a countrywide basis (Goodrich et al. 2015).
Sanderson et al. (2006) put forward the concept of establishing Tiger Conservation
Landscapes (TCLs) and estimating tiger populations across their entire range using
multiple methods; from expert opinion to land cover (e.g., vegetation) and change
assessments based on satellite sensor data. The study also highlighted that 76 TCLs
held the major tiger subpopulations in the world. An additional 543 fragments were
also identified, but they were considered too small to support long-term viable populations. 491 areas were designated as Tiger Survey Landscapes (TSL; total area of
1.1 million km
2
), where the current tiger status was unknown but the area was considered sufficiently large to support at least five tigers. The study highlighted that it
Coupling Field Sampling with Earth Observation Increases Understanding of Tiger…
extinction because of their low densities (relative to other mammals, including their
prey species) and relatively low recruitment rates (where few animals raise offspring that survive to join the breeding population) (Kerley et al. 2003). Tigers also
require large undisturbed landscapes with ample prey to raise young and maintain
long term genetic and demographic viability (Seidensticker and McDougal 1993;
Karanth and Sunquist 1995; Carbone et al. 1999; Jhala et al. 2008). However, such
areas are contracting or becoming increasingly fragmented because of high anthropogenic pressures on natural resources. Whilst India has the world’s largest population of wild tigers, it has also suffered the highest range contraction for the species.
Poaching is mainly for the supply of organs, bones and hides that are smuggled for
use in traditional medicine, mainly into China and south-east Asia (Gratwicke et al.
2008; Nowell 2009).
Efforts to save the tiger started rather late. For example, Project Tiger was initiated in India in 1973 (GOI 2005). However, the strategies used were not time-tested
and were also often weak on scientific rigor, partly because of a general lack of
baseline information on tiger distributions (ibid). Conservation strategies for tigers
had previously focused only on protecting the species in pristine wilderness areas
and were based on the premise that estimates of tiger densities derived from signbased indices (e.g., pugmark census techniques) were adequate to provide information on the survival status of the species. However, detecting tigers through
traditional field survey methods is a challenging task. Tigers require sufficient numbers of large-bodied prey and therefore roam across large that may exceed 100s of
kilometres. They also occur in low densities and often as lone individuals, particularly in closed forests (Gittleman and Harvey 1982; Carbone et al. 2001), are cryptic
by nature and are rarely seen. As a consequence, records relating to tiger distributions and their use of habitats have been inadequate and this has severely impeded
the formulation and implementation of appropriate conservation measures (Blake
and Hedges 2004; Sanderson et al. 2006).
For these reasons, there has been an increasing and now urgent need to devise
rapid yet rigorous population analysis and viability methods with spatial and temporal observations that are repeatable across the varied landscapes that tigers occupy
(Linkie et al. 2006). It is also widely accepted that a landscape approach to tiger
conservation that takes into account the distribution and condition of habitat also
fares better than those that focus only on protecting the species. Although breeding
populations are currently found in eight Asian range states, there are few regular
empirical studies to indicate trends on a countrywide basis (Goodrich et al. 2015).
Sanderson et al. (2006) put forward the concept of establishing Tiger Conservation
Landscapes (TCLs) and estimating tiger populations across their entire range using
multiple methods; from expert opinion to land cover (e.g., vegetation) and change
assessments based on satellite sensor data. The study also highlighted that 76 TCLs
held the major tiger subpopulations in the world. An additional 543 fragments were
also identified, but they were considered too small to support long-term viable populations. 491 areas were designated as Tiger Survey Landscapes (TSL; total area of
1.1 million km
2
), where the current tiger status was unknown but the area was considered sufficiently large to support at least five tigers. The study highlighted that it
Coupling Field Sampling with Earth Observation Increases Understanding of Tiger…