Corridors with high human activities may not ease elephant connectivity:
Rupsy Khurana, Mongabay
May 9, 2022
Drawing attention to the restriction of elephant movement due to
development and infrastructure barriers, scientists studying genetic
differences between elephant populations in the country have expressed
concern over genetic differences in populations arising even over small
distances separating the megaherbivores.
In India, where a large extent of elephants lie outside protected areas,
elephants occur in the country’s north-western, east-central, north-eastern
and southern regions with the latter two holding about 80% of the elephant
population. A study conducted by Surendra Prakash Goyal and his team from
Wildlife Institute of India, suggests that these four populations are
genetically different from each other which is expected since they are
geographically separated over more than 2000 kilometres.
However, the authors flag some genetic differences within northwest,
northeast and south India populations which could be a result of limited
genetic connectivity caused by rampant development and infrastructure
Researchers collected dung samples from two sites in the northwest
(Uttarakhand and Uttar Pradesh), two in the northeast (West Bengal and
Assam), two sites in central (Odisha) and 10 in south India (Karnataka,
Kerala, Tamil Nadu). They extracted DNA from the samples and ran multiple
laboratory procedures to identify genetic clusters of Asian elephants in
Factors such as geographic distance, habitat characteristics such as
quality of forest, resource distribution such as best quality and quantity
of food, availability of water and mates, and mate choice can limit gene
flow, says Goyal. The presence of natural barriers such as rivers or
human-made barriers such as highways, concrete walls and electric fences
can also result in genetic differentiation among populations, he added.
Ill-conceived development that leads to forest loss and fragmentation
affects elephant movement across landscapes and hinders genetic
Small populations in disconnected habitat patches suffer from loss of
genetic diversity which could wipe out the entire populations from these
small patches. Inbreeding, where related individuals mate over and over
since no animals can move from or to nearby populations, increases the risk
of mortality, and susceptibility to sudden environmental changes and
diseases, suggested Rahul Dey, lead author of the study.
How Barriers Disrupt Elephant Movement Across India
The northwest range of elephants consists of the outer Himalayas, Shivaliks
and parts of Terai in Uttarakhand and Uttar Pradesh. The study found that
elephants in the Shivalik elephant reserve in Uttarakhand and Katarniaghat
wildlife sanctuary in Uttar Pradesh, only 120 km apart, face barriers to
The differences between Shivaliks and Katarniaghat populations can be
chalked up to the presence of the Torsa river. However, within Shivaliks,
highways, roads and encroachments are major drivers of the genetic
differences in elephants in Rajaji Tiger reserve and Lansdowne Division-
Corbett Tiger reserves.
Genetic clusters are expected over large distances, says Priya Davidar, an
author of the study. However, observing such patterns over a few hundred
kilometres suggests the presence of barriers to animal movement, she added.
In northeast India, elephants inhabit the forests and grasslands of
Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland and
Researchers collected samples from Baikunthapur Forest Division (northeast
West Bengal) and Jeypore reserve forest (Assam), about 650 km apart, and
concluded that the genetic makeup of the two populations was different.
In south India, elephant populations are distributed over hilly tracts of
the Western Ghats and parts of the Eastern Ghats in Kerala, Tamil Nadu,
Karnataka and Andhra Pradesh. Northern Karnataka is the northern limit of
elephant distribution in south India.
The authors found that elephants in the Nilgiri Biosphere reserve
(Nagarhole National Park, Biligiriranganatha Swamy Temple Wildlife
Sanctuary, Wayanad Wildlife Sanctuary, Sathyamangalam and Mudumalai Tiger
Reserve, Sigur and Coimbatore Forest Division) formed one cluster. Whereas
elephants in Periyar, Kalakkad Mundanthurai and Anamalai Tiger reserves
together have a different genetic makeup.
These two genetic clusters (Nilgiris and Periyar/Mudanthurai/Anamalai) are
separated by the Palghat Gap, a break in mountain chains of the Western
Ghats which acts as a natural barrier to the connectivity of elephants and
other species. However, it is alarming that there are minor differences in
the geographically connected Anamali and Periyar populations. The team
suggests that this loss of connectivity could be due to agriculture
expansion that has occurred within the last century.
Moving forward towards Kalakkad Mundanthurai Tiger reserves, the elephants
face the same fate. The Shencottah gap, a mosaic of degraded forests,
linear infrastructure and human establishments hinders elephant
Though S.P. Goyal and his team picked up some signatures of inbreeding in
northeast elephant populations, the data was based on a few samples and
might not be as robust.
Maintenance of Corridors
In the wake of splintered habitats, the preservation of critical habitat
patches and strips of suitable habitats (corridors) that link them is
indispensable for the long-term sustenance of species. Managing corridors
at a fine scale while addressing socio-ecological aspects is crucial for
animals to move and persist in a landscape.
These genetic differences at finer scales are evidence that built-up areas,
infrastructure elements (roads, railway lines etc), and encroachments of
corridors are impacting connectivity.
As per a report published in 2017, there are more than 100 elephant
corridors in elephant landscapes. Of these, 28 are in south India, 25 in
central India, 23 in northeastern India, 14 in northern West Bengal and 11
in northwestern India, yet the study reported genetic differentiation in
populations over small distances, highlighting the need for re-evaluation
and maintenance of corridors.
“Elephants are wide-ranging and corridors are crucial for them. But, there
is not that much being done to save their corridors. Our work, for
instance, on corridors in Garo Hills, shows the significant limitation to
elephant movement over small distances, if there are no forests,” says
Divya Vasudev, Senior Scientist, Conservation Initiatives. She was not
associated with the study.
Although the presence of corridors in the landscape is indubitable,
anthropogenic disturbances such as agricultural fields, tolerance by
locals, mining operations, and the absence of cover and forage in the
corridors, ultimately guide the ease of animal movement. Of these 100
elephant corridors, about 45% have some form of human-caused disturbance.
Some of these corridors are as trivial as 0-100 meters in
Chamrajanagar-Talamalai at Punjur (Karnataka). “We need better
identification of corridors, forestland that plays a critical role in
connectivity either as corridors or stepping stones and ensuring no loss of
forests in these areas,” Vasudev added. The existence of corridors with
high human pressure may not translate into effective use by animals and
hence does not ensure connectivity.
“Animal presence in the corridors connecting two habitat patches does not
mean that a corridor is functional. Elephants avoid degraded habitats,
densely populated areas, and linear infrastructure that hinder their
movement. Measuring the exchange of gene flow between two populations
connected through a corridor can help evaluate the efficiency of the
corridors in maintaining connectivity,” Sandeep Sharma, German Centre for
Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig, Germany, told
At present, only 12.9% of the corridors are totally under forest cover as
compared to 24% as per a study conducted in 2005. About 66% of the
corridors have state or national highways passing through them.
“Incorporating connectivity into the proposed amendments of the Wild Life
Protection Act, such that there is legal recognition of connectivity and
corridors, is crucial for maintaining corridors. In addition, securing
animal movement outside corridors is also crucial which would involve
stakeholders, local community members and landowners,” said Vasudev.
Though 14 proposed corridors in Odisha are still awaiting legal status,
Sharma says, “After notification, corridors need to be maintained through
law and order, proactive management plan, recognising eco-sensitive zones
around corridors and banning any new development in the area.”
The area required for the expansion of Jolly grant airport falls within the
Shivalik elephant reserve and is in proximity to Kansaro-Barkot Elephant
Corridor. In addition to human activities, climate change might trigger
loss of habitats compounding threats to Asian elephant populations in
Reeta Sharma, another author of the study emphasises that “climate change
would potentially exacerbate the current threats in combination with
anthropogenic activities, especially in east-central and north-west India.
Agricultural expansion, infrastructure development, mining and
human-elephant interactions are common problems in both areas.”
However, east-central populations require conservation prioritisation due
to the greater extent of habitat fragmentation and the predicted risk of
about 80% habitat loss, the authors emphasise. The population has lower
genetic diversity compared to north-western and southern elephant
populations, habitat is prone to frequent human-elephant interactions and
is under threat by developmental activities, says the team.
As climate change affects agricultural outcomes like crop failure, the
dependence of people on NTFP might increase, worsening the risk to
corridors since they are accessible and under no legal protection, said