Road kill of animals by highway traffic in the
tropical forests of Mudumalai Tiger Reserve, southern India
N. Baskaran 1 & D.
Boominathan 2
1 Bombay Natural History Society, Elephant
Project, Bear Bungalow, Kargudi, The Nilgiris, Tamil Nadu 643211, India
Present Address: Asian Elephant Research and
Conservation Centre, a Division of Asian Nature Conservation Foundation,
Innovation Centre First Floor, Indian Institute of Science, Bengaluru,
Karnataka 560012, India
2 Department of Zoology, AVC College,
Mannampandal, Mayiladuthrai, Tamil Nadu 609305, India
Present Address: World Wide Fund for Nature - India,
Nilgiris and Eastern Ghats Landscape Programme, Lamp Society Building,
Masinagudi, The Nilgiris, Tamil Nadu 643223, India
Email: 1 nagarajan.baskaran@gmail.com, 2nathan_d1@rediffmail.com
Date
of publication (online): 26 February 2010
Date
of publication (print): 26 February 2010
ISSN
0974-7907 (online) | 0974-7893 (print)
Editor: R.J. Ranjit Daniels
Editor’s Note: The paper has been included, despite the
data being 10 years old, only to highlight the magnitude of the problem - a
problem that might be many times higher at present and not really addressed.
Manuscript details:
Ms
# o2101
Received
26 November 2008
Final
received 11 February 2010
Finally
accepted 13 February 2010
Citation: Baskaran, N. &
D. Boominathan (2010). Road kill of animals by highway traffic in the tropical
forests of Mudumalai Tiger Reserve, southern India. Journal of Threatened Taxa 2(3): 753-759.
Copyright: © N. Baskaran &
D. Boominathan 2010. Creative Commons Attribution 3.0 Unported License. JoTT
allows unrestricted use of this article in any medium for non-profit purposes,
reproduction and distribution by providing adequate credit to the authors and
the source of publication.
Author Detail: Dr. N. Baskaranis presently a Sr. Scientist at the ANCF, studying Asian Elephant and its habitats across Western and Eastern
Ghats and Eastern Himalayas landscapes since 1990. Mr. D. Boominathanis presently a Sr. Project Officer in Western Ghats Landscape Program of WWF,
studying the human–elephant conflict since 2003.
Author Contribution: The
first author designed the study, compiled the data and wrote this manuscript,
while the second author conducted the field surveys of this study during his
Master of Science degree.
Acknowledgements: We are thankful to the Forest Department
of Tamil Nadu especially to Mr. P.S. Katwal IFS, former Chief Wildlife Warden
and Mr. A. Udhayan IFS, former Wildlife Warden, Mudumalai Wildlife Sanctuary
for permitting the study. We thank
Mr. A.A. Desai, Co-chairman IUCN Asian Elephant Specialist Group for his
valuable suggestion to the study. We also acknowledge the help rendered by Mr.
S. Swaminathan, Bombay Natural History Society and Mr. R. Arumugam and Dr. C.
Arivazhagan, Indian Institute of Science during the fieldwork and Mr. Avinash
K.G., Asian Nature Conservation Foundation for GIS support.
For Image & Tables –
click here
Introduction
Highways across
wildlife refuges are an intrusion and affect the wildlife and its habitats
adversely. The effects range from
habitat loss and fragmentation (Burnett 1992; Richardson et al. 1997; Carr
& Fahrig 2001) to affecting the wild animal distribution pattern (Newmark
et al. 1996), movement (Desai & Baskaran 1998), breeding density (Reijnen
et al. 1995), heterozygosity, genetic polymorphism (Reh & Seitz 1990) and
directly by mortality through collisions with vehicles (Oldham & Swan 1991;
Foster & Humphrey 1995; Das et al. 2007; Row et al. 2007; Shwiff et al. 2007; Seshadri et
al. 2009). The taxa affected
ranges from mammals (Newmark 1992; Drews 1995; Newmark et al. 1996; Richardson
et al. 1997) to birds (Reijnen et al. 1995; Drews 1995), reptiles (Rosen &
Lowe 1994; Drews 1995; Gokula 1997; Das et al. 2007) and amphibians (Reh &
Seitz 1990; Fahrig et al. 1995; Seshadri et al. 2009). More attention has been paid in North
America, Australia, Europe and Africa to assess such impacts but Asia has not
given the required attention to this aspect. In India, highways bisect many protected areas. It has been realized in recent years
that highways cause severe impact to wildlife and their habitats (Gokula 1997;
Gruisen 1998a Vijayakumar et al. 2001; Das et al. 2007). Therefore, the forest departments and
non-governmental organizations in India are protesting against the construction
of new highways and also the upgrading or widening of the existing roads in
especially protected areas.
Mudumalai Tiger
Reserve with adjoining reserved forests of Nilgiri North and Sathyamangalam
forest divisions forms an important part of the Nilgiri Biosphere Reserve
(located at the tri-junction of three southern states of Karnataka, Kerala and
Tamil Nadu) (Desai & Baskaran 1996). The Mudumalai Tiger Reserve has several roads including an inter-state highway
cutting through the reserve. These
roads have been identified as the source of disturbance to wildlife both
directly (road kills including that of endangered species) (Gokula 1997) and
indirectly (noise and disturbance) (Daniel et al. 1995). Most of these observations are very subjective in nature, though
undoubtedly, these roads have an adverse impact on wild animals (Daniel et al.
1995; Gokula 1997; Desai & Baskaran 1998). However, the actual impact has not been quantified. Furthermore, there is also a proposal
to develop a highway to connect Mysore (Karnataka) and Kozhikode (Kerala)
Cities to Coimbatore City (Tamil Nadu) via Masinagudi, Anaikatty, Sigur and
Bhavanisagar. At present, there is
a road up to Sigur, but traffic level is comparatively less as this road ends
at the village.
The proposal to
divert the state highway from the Sariska Tiger Reserve in Rajasthan is a
classic example of the highway impact on wild animals in India. In less than a year, one tiger Panthera tigris and
two leopards Panthera parduswere killed by speeding vehicles on the state highway at Sariska Tiger Reserve
(Gruisen 1998a).
The present study
was carried out between December 1998 and March 1999, to evaluate the impact of
vehicular traffic on vertebrate fauna in terms of animals killed by
automobiles.
Although the
study was carried out over a decade ago, the results are still important for
the following reasons: there exists no detailed published data yet on the
effects of vehicular traffic on the vertebrate fauna for the protected areas in
the Nilgiri Biosphere Reserve, (which is part of the Nilgiri-Eastern Ghats and
one among the developed landscape in Asia) (Leimgruber et al. 2003) with high
biomass of large mammals. Further,
with the recent economic growth of the nation, the traffic intensity would have
increased substantially compared to the study period (1998–99) thus the published results would
enhance the comparison of the present effect of highway traffic on the wildlife
with the past findings to understand the current trend.
Study Area
The Mudumalai Tiger Reserve is part of the Nilgiri
Biosphere Reserve of the Western Ghats. It lies between 11032’-11042’N
& 76020’-76040’E and is situated at the junction of
three southern states, viz. Tamil Nadu, Kerala and Karnataka. The Reserve is surrounded by Bandipur
Tiger Reserve in the north, Wayanad Wildlife Sanctuary in the west and Nilgiri
North Forest Division in the east and south (Image 1) and covers an area of
321km2, with an average elevation of 900–1000m. Moyar, the perennial river of the
sanctuary flows eastwards. The
sanctuary has three marked seasons, viz. dry season (January–April),
southwest monsoon (May–August) and northeast monsoon
(September–December). The
annual rainfall varies from 600mm in the east to 2000mm in the west. Corresponding to the rainfall gradient,
the vegetation changes from thorny scrub in the east, dry deciduous in the
middle to moist and semi-evergreen forests in the west. The sanctuary with diverse vegetation
types supports a large faunal assemblage including high abundance of threatened
species like the Asian Elephant Elephas
maximus and Indian Tiger.
Methods
Selection of study roads
Three public roads located within the reserve were selected
for quantifying the road kills and these include (1) an inter-state highway
segment A–B), (2) a state highway (segment C–D), and (3) a
secondary road (segment E–F) (Image 1). The inter-state highway connects the cultural capital of
Karnataka, Mysore City, with the well-known hill station of southern India,
Udhagamandalam, popularly known as Ooty (Image 1). The inter-state highway cuts through the forest areas of
Karnataka (Bandipur Tiger Reserve) and Tamil Nadu, where it enters the
Mudumalai forest in the north at the border post of Kekkanhalla and goes beyond
the forest limits at Thorappalli. The stretch from Kekkanhalla to Thorappalli that runs through the
reserve for a total length of 16km with a relatively higher traffic intensity
was identified as the inter-state highway sampling segment. The inter-state highway branches into a
state highway at Teppakadu, leading to Udhagamandalam and beyond via
Masinagudi, a small town. The
stretch of 7km between Teppakadu and Masinagudi was identified for the state
highway sampling segment. The
third sector of 8km road that connects Masinagudi and Moyar was used as the
secondary road sampling segment. Traffic intensity is less on this road compared to the inter-state and
state highways. These three roads
are different in their surrounding habitats and microhabitats but represent
different networks of highways traverse through the reserve.
Quantification of road kills
To quantify the direct impact of roads on wild
animals, the number of road kills that occurred on three roads were counted.
The study was restricted to amphibians, reptiles, birds and mammals. To quantify the road kills, the three
roads were surveyed systematically between 0600 and 0900 hr twice a month at
fortnightly intervals for four months from December 1998 to March 1999. In addition, using opportunistic
sampling method, data on road kills (mostly mammals) were also collected during
incidental visits and based on the information received from other researchers,
department staff and local people. At every sighting of a road kill, information such as place, species
name, number and status of the kill was recorded. The status of the kill was classified into two categories,
such as fresh (killed within the last 24 hours) and old (killed more than 24
hours earlier) based on the condition of the carcass such as tissue and skin
texture (soft/hard), and blood conditions. After recording the above details, the carcass was removed
from the road and if unidentified, it was preserved in formalin for later
identification. A total of 128, 56
and 64 km distances were walked respectively, on the inter-state highway, state
highway and secondary road during the study period. Data on road kills collected on fortnightly and
opportunistic sampling methods from the three roads during the study period
were collated separately to arrive at the total number of road kills recorded
in each sampling method.
Results
Road kills
In total, 180 road kills belonging to 40 species were
recorded both during periodic transect survey and opportunistic sampling
methods (Table 1). Of the 180 road
kills, 99 were recorded through fortnightly surveys of the three roads (248km)
over four months. The remaining 81
road kills were recorded through opportunistic sampling. Among the 180 road
kills, amphibians were the most affected accounting for 53%, followed by
reptiles (22%) and mammals (18%). Birds were least affected by vehicular traffic and comprised 7% of the
total kills. In terms of the
number of species, reptiles (16 species) stood topmost followed by mammals (13
species) (Table 1). These figures
are probably an underestimate given that an unknown proportion of animals hit
by vehicles are either eaten by carrion feeders or died in the nearby
vegetation without being recorded. Among the road kills recorded, the Common Indian Toad Dattaphrynus melanostictus was the
most susceptible species for the vehicular traffic (Table 2), which accounted
for over 50% of the total road kills. It is important to note that vehicles killed endangered carnivores such
as an adult Leopard and a Palm Civet Paradoxurus
hermaphroditus during the four-month study period. Reptiles such as the Common Wolf Snake Lycodon aulicus,
Common Garden Lizard Calotes
versicolor, birds such as Indian Myna Acridotheres tristis,
Spotted Dove Streptopelia
chinensis, Yellow-throated Sparrow Petronia xanthocollis and Common Indian NightjarCaprimulgus asiaticus,
and mammals such as mouse Mussp. were the most affected species. Among larger mammals, primates such as the Crested Grey Langur Semnopithecus priamand Bonnet Macaque Macaca
radiata were highly affected, accounting for nine kills during
the study period.
To understand the effect of highway stretches,
especially those running parallel to a water source, on the wild animals, the
number of road kills recorded in a sub-section of a given road (inter-state
highway) running parallel to the river Moyar (between Teppakadu and Kargudi of
3.2km) was compared with a sub-section of the same road traversing away from
water bodies (between Bidarhalla and Thorappalli of 5.1km) with similar
adjoining major habitat conditions (Image 1). The sub-section of the road traversing parallel to water
sources (between Teppakadu and Kargudi: 7.1 kills/km) experienced a significantly
more number of road kills/km than the sub-section of the same road traversing
away from water bodies (between Bidarhalla and Thorappalli: 1.8 kills/km) (X2 = 4.00, df = 1, P < 0.05) with no variation in species
composition. The results indicate
that highways located parallel to water sources in a nature reserve are more
detrimental to wild animals than those away from water areas.
Discussion
The data on road
kills revealed that vehicular traffic killed a minimum of 180 individuals of
vertebrate fauna amphibian, reptile, bird and mammals of the reserve in four
months. A study on road
mortalities of snakes in Mudumalai carried out over six months (Gokula 1997)
shows that out of seven species of snakes, the Common Vine Snake Ahaetulla nasutus was
the most affected (12 out of 23 snake road kills) and estimated at 0.25
snakes/km in 24 hours. In
contrast, our study recorded 13 species of (27 individual) snakes with the
Common Wolf Snake as the most affected species (seven road kills) in the
four-month period. The difference
could be attributed to the variation in sampling period, effort and the survey
area. The most affected vertebrate
fauna in the present study was amphibians (53%) followed by reptiles (22%),
mammals (18%) and birds (7%). The
higher road mortality of amphibians and reptiles could be attributed to their
slow mobility, not reacting quickly to vehicles and the fact that drivers are
less likely to notice these animals because of ignorance. Among the reptile road kills, snakes
(13 out of 16 species) accounted for the highest (67%). A similar finding has been made by Das
et al. (2007) at Kaziranga National Park, northeastern India who attributed the
slow movement and use of roads as substrate for thermo-regulation by snakes for
the higher mortality. Rosen &
Lowe (1994) estimated ten to hundreds of millions of snakes having been killed
by automobiles in the United States and reasoned that resting or coiling of snakes
on the road surface especially during spring season for warmth is a
contributing factor to the high road mortality of snakes. Lower susceptibility of birds to
vehicular hits could be due to their ability to fly fast.
Among the
amphibian road kills recorded in the present investigation, Duttaphrynus melanostictuswas the most affected (98%), as reported in another study in the Anamalai Hills
(Vijayakumar et al. 2001). Our
results, though arguably due to the higher ‘relative abundance’ of this
species, here in this area, perfectly accord with Vijayakumar et al. (2001),
wherein the family Bufonidae, represented solely by D. melanostictus constituted up to almost half
(46.6%, n =
144) of total amphibian road kills in Anaimalai Hills, which is present ca. 150
airline km southwest of our study area. The foraging nature of these toads, which are very fond of gathering
near street lamps and vehicle head lights to feast on insects (Daniels 2005) coupled with their highly eurytopic
and human commensally traits (Daniel 2002; Daniels 2005) could also be the possible
reasons for their higher susceptibility of becoming road kill victims. Among the mammalian fauna, the Bonnet
Macaque and Crested Grey Langur come close to the road to beg from tourists
leading to higher incidents of mortality due to highway traffic, as reported
for Yellow Baboons in Mikumi National park, Tanzania (Drews 1995). Sometimes the sudden movement of langur
across the road also contributes to high mortality of this species (N. Baskaran
pers. comm.). Most of the
mammalian road kills recorded in the present study are nocturnal (mouse,
bandicoot, Black-naped Hare, Sambar, Leopard, Palm Civet and bat) species that
could have been killed while crossing the roads, as they get blinded by the
vehicle’s headlights. Besides an
adult leopard, a leopard cub at Mudumalai Tiger Reserve in February 1998 and an
adult tiger at Bandipur, were killed by speeding vehicles in 2006 (N. Baskaran
pers. obs.). Though these figures
seem to be very small compared to other species, such loss is unbearable
considering their low population density. There are several places where large cats have been killed by highway
traffic in India. In Sariska Tiger
Reserve, Rajasthan, one tigress and two leopards were killed by highway traffic
in a year (Gruisen 1998a) and several leopards in a two-month period in Corbett
National Park, Uttar Pradesh (Gruisen 1998b). Similarly, in Florida, collision with motor vehicles is a
major cause of mortality of the endangered Florida Panther Puma concolor coryi, accounting for
49% of the documented deaths (Maehr et al. 1991). In Africa, endangered species such as the African Elephant Loxodonta africana (n = 2), Wild dog Lycaon pictus (n = 3) and Panthera leo krugeri (n = 1) were killed by
vehicles during a period of 19 months (Drews 1995). These reports indicate that such problems are increasing in
recent years.
The present study
is preliminary in nature as it was a short term study and has some caveats like
actual rate of mortality per day and seasonal variability on the rate of road
kill which could not be worked out. A more detailed year round study will enable us to understand better the
impact of vehicular traffic. Nevertheless, this study indicates that roads have a high impact on
wildlife.
Conclusions and Recommendations
The
present study shows that highways have adverse impact on wildlife including
endangered species. During the
four-month study, a leopard was killed by highway traffic apart from other
endangered species. Earlier
records indicate that Tiger, Leopard, Sloth Bear, Leopard Cat, Small Indian
Civet and Gaur have been killed by vehicular traffic. We make the following recommendations apart from simple
measures like speed limits, breakers and adequate signposts at the roadsides of
the reserve:
-
It is not advisable to permit any changes in the existing highways that would
increase the traffic load or speed limit as such changes will increase road
kill rate further. Additionally,
the proposed new highway to Coimbatore via Masinagudi, Sigur, Bhavanisagar should not
be developed as alternative highways already exist (from Kozhikode to
Coimbatore via Palghat and Mysore to Coimbatore via Chamarajnagara and Hasanur)
and the new highway would increase the traffic load, both in Mudumalai and
Bandipur Tiger Reserves.
-
Including the first author’s experience in Mudumalai since 1990 on an elephant
ecology long-term study (Daniel et al. 1995), we have come across a large
number of road kills in addition to the fact that wild animals including
elephants have to wait for long hours due to vehicular traffic to access the
water source especially between Teppakadu and Kargudi. Here the highway runs parallel to Moyar
River. We suggest the construction
of fly-overs for vehicular traffic across the traditional footpaths of wild animals
(Kalhalla, Nadu–camp and Kargudi watchtower) leading to Moyar River to
reduce the road kill rate as well as to improve the access of the water source
to wild animals.
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