Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 November 2021 | 13(13): 20072–20077
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.6937.13.13.20072-20077
#6937 | Received 26 November 2020 | Final
received 07 October 2021 | Finally accepted 19 October 2021
A rare photographic record of
Eurasian Otter Lutra lutra
with a note on its habitat from the Bhagirathi Basin, western Himalaya,
India
Ranjana Pal 1, Aashna Sharma 2, Vineet Kumar Dubey 3,
Tapajit Bhattacharya 4, Jeyaraj Antony Johnson 5, Kuppusamy
Sivakumar 6 & Sambandam Sathyakumar 7
1,2,3,5,6,7 Wildlife Institute of India, Chandrabani, Dehradun 248001, Uttarakhand, India.
4 Durgapur Government College,
Durgapur, West Bengal 713214, India.
1 ranjana.biocon@gmail.com, 2 aashna.wildlife@gmail.com,
3 vineetkrdubey@gmail.com, 4 tapajit@gmail.com , 5 jaj@wii.gov.in,
6 ksivakumar@wii.gov.in, 7 ssk@wii.gov.in (corresponding
author)
Editor: Nicole Duplaix,
Fisheries & Wildlife, Corvallis, USA. Date
of publication: 26 November 2021 (online & print)
Citation: Pal, R., A. Sharma, V.K. Dubey,
T. Bhattacharya, J.A. Johnson, K. Sivakumar & S Sathyakumar
(2021). A rare photographic record of
Eurasian Otter Lutra lutra
with a note on its habitat from the Bhagirathi Basin, western Himalaya, India. Journal of Threatened Taxa 13(13): 20072–20077. https://doi.org/10.11609/jott.6937.13.13.20072-20077
Copyright: © Pal et al. 2021. Creative Commons Attribution
4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: Department of Science
and Technology (DST), Government
of India, National Mission for Sustaining Himalayan Ecosystem (NMSHE),
Grant No.
DST/SPLICE/CCP/NMSHE/TF-2/WII/2014/[G].
Competing interests: The authors
declare no competing interests.
Acknowledgements: This work is part of project
initiated under the National Mission for Sustaining the Himalayan Ecosystem
Programme funded by the Department of Science and Technology, Government of
India under grant no. DST/SPLICE/CCP/ NMSHE/TF-2/WII/2014[G]. We are thankful
to the director and dean, Wildlife Institute of India, for their guidance and
support. We are grateful to Mr. D.V.S. Khati,
principal chief conservator of forests and chief wildlife warden, Uttarakhand,
for granting us the research permission and Mr. Shrawan
Kumar, Mr. N.B. Sharma, deputy director, Gangotri National Park, and Mr.
Sandeep Kumar, divisional forest officer, Uttarkashi, for providing necessary
support and cooperation. We thank Dr. S.A. Hussain
and Ms. Sayanti Basak for
their help in identification of the species.
Abstract: The Eurasian Otter Lutra lutra is an
elusive, solitary animal that has one of the widest distributions of all
palearctic mammals. Once widely distributed in Asia, the Eurasian Otter population
is now vulnerable to urbanization, pollution, poaching, and dam construction.
Eurasian Otter distribution in the Indian Himalayan rivers is little explored,
and information from this high-altitude riverine ecosystem is sparse. This
publication reports a rare photographic record of the Eurasian Otter which
confirms its presence in the high-altitude temperate forest of the Upper
Bhagirathi Basin, western Himalayan region. The otter was recorded during
investigations of terrestrial and aquatic fauna in the Bhagirathi Basin (7,586
km2, 500–5,000 m) of Uttarakhand State, India from October 2015 to
May 2019. Among aquatic fauna, Brown Trout were found to be abundant in high
altitude river stretches, with a catch per unit effort of 1.02 kg h–1. Additionally, 26 families of freshwater
macroinvertebrates underscored a rich diet available for the Brown Trout, which
in turn is a potential food source for the otters. The riverine ecosystem is
undergoing dramatic changes because of the increasing demand for hydropower
plants in the Bhagirathi Basin. Although mitigation measures are currently in
place for fish, the presence of otters further necessitates the need for
targeted management for high-altitude Himalayan rivers. There is an imperative
need for intensive otter surveys using methods such as camera traps in riparian
habitats along the Bhagirathi River and its tributaries.
Keywords: Anthropogenic pressures, camera trapping, hydropower
projects, otter, riverine ecosystem.
Information on otters of the
high-altitude riverine ecosystems in the Indian Himalayan region is lacking.
Eurasian Otter Lutra lutra
(Linnaeus, 1758), is the only otter found in high altitude (>2,000 m)
mountain streams and rivers (Prater 1971). The
species has the widest distributions of all palearctic mammals (Corbet 1966);
however, due to human pressures, they have disappeared from most of their range
(Yoxon & Yoxon 2019).
There is lack of information about its population status in Asia, where it is
believed to be under tremendous pressure because of poaching (Roos et al.
2015). The species is classified as ‘Near Threatened’ on the IUCN Red List, and
is vulnerable to the pelt trade (Roos et al. 2015), climate change (Gupta et
al. 2020), and habitat destruction & pollution (Roos et al. 2015). It
is listed in Appendix I of CITES, and in India, is listed in Schedule II (Part
2) of the Wildlife (Protection) Act, 1972.
Scattered records across Asia are
indicative of otter distribution along all the major river systems, ranging to
the southernmost parts of Sumatra, Indonesia (Corbet & Hill 1992). However,
its distributional range in the Indian Himalayan region is still unclear, with
research suggesting that it is mostly confined to river plains and foothills
(Atkinson 1882; Hussain 2002) with the exception of a few high-altitude records
from the Trans-Himalayan regions of Ladakh and
Himachal Pradesh (Conroy et al. 1998). The earliest records of otter from the
state of Uttarakhand (Atkinson 1882) date to the 19th century, when
they were recorded from the Ramganga River and Dehradun. According to Atkinson
(1882), the Eurasian Otter was found throughout the Terai
and in all the larger streams along the Himalayan foothill. Apart from its
distribution in the Indian Himalayan region, this species has been recorded
from the northern mountainous region of Pakistan and Punatshanghchu
basin of Bhutan (Yoxon & Yoxon
2019). There are no recent confirmed records of the Eurasian Otter from Nepal (Yoxon & Yoxon 2019). Based on
their distribution records from mountainous habitats in neighbouring regions
(Image 1), their presence was long anticipated in the high-altitude river
systems of Uttarakhand state. However, studies in low elevation areas have
indicated that otters have declined drastically from most stretches of the
rivers in Uttarakhand due to habitat loss/degradation caused by hydropower
projects, anthropogenic pressures, and poaching (Nawab 2008; Chopra et al.
2014). Recent attempts to confirm otter presence in lower part of Bhagirathi
and adjacent Alaknanda basin using sign surveys
yielded no sightings or any indirect evidence of their presence, although
suitable habitats were found in both the basins (Hussain 2002; Rajvanshi et al. 2012).
Here, we report a photographic
record of Eurasian Otter from the high-altitude temperate forest of the Upper
Bhagirathi River Basin, Uttarakhand state. The study is the part of a long-term
monitoring of wild flora and fauna under the National Mission for Sustaining
the Himalayan Ecosystem (NMSHE) project (Task force IV). Surveys were carried
out in different areas of Bhagirathi Basin (7,586.71 km2), to
develop baseline information on faunal species of terrestrial and aquatic
components. Based on their records specifically from the high-elevations in
other basins of Himalaya, we also aimed to understand the habitat availability
in our study area, as well as the potential faunal composition which supports
the dietary needs of the Eurasian Otter in such landscapes. As such the camera
trapping surveys were paralleled with the aquatic habitat, fish and
macroinvertebrate faunal surveys to investigate the reasons dictating their
rare preference for the high-elevation streams and rivers of Himalaya.
Materials and Methods
The Bhagirathi is a large glacial
fed and turbulent Himalayan river that emerges from Gangotri glacier (Gaumukh), 30.9250N & 79.0820E at
an elevation of 3,812m. The valley has a broad U-shape at higher elevations
characteristic of glacial origin, but at lower elevations the river has cut a
narrow V-shaped fluvial valley. Along the 217km long river the elevation ranges
from 480m to 3,200m with an average gradient of 1.25% (Rajvanshi
et al. 2012). The basin encompasses diverse habitats: tropical and sub-tropical
forests (500–1,200 m), temperate forests (1,200–2,800 m), sub-alpine forests
(2,900–3,200 m), alpine scrub and meadows above 3,200 m (Rajwar
1993). Human habitations in the study area are confined below the elevation of
3,000 m (Image 1).
Data on the seasonal distribution
of mammal species were collected using camera traps (Cuddeback
C1, WI, USA) from October 2015 to March 2019 broadly covering two seasons: summer
and winter. Camera trapping was carried out in two stages. In the first stage
(October 2015–September 2017), preliminary survey for all the mammals was
carried out along the elevation gradient of 500 m to 5,200 m. At each site,
camera traps were deployed in locations likely to be used by animals inside the
forest, alpine meadows, along the river beds and other such microhabitats (Sathyakumar et al.
2013). In the second stage (October 2017 to March 2019), camera traps
exercise was carried out only in the high elevation habitats (2500 m to 5200 m)
targeting Snow Leopard Panthera uncia, Leopard Panthera
pardus, and their prey species. To survey evenly
across the various habitats, we divided the basin into 16 x 16 km grids, which
corresponds to the average home range of the largest mammal in the area, the
Himalayan Brown Bear Ursus arctos isabellinus. We
subdivided these cells into 4 × 4 km (first stage) and 3 x 3 km cells (second
stage) deployed camera traps in 3–6 of these smaller cells within each 16 x 16
cell. A total of 318 locations were sampled during this period (Image 1).
Simultaneously, fish and
macroinvertebrate sampling was also conducted in the river stretches of
Bhagirathi Basin. Rivers were sampled from March 2016 to December 2018 at every
500 m for the higher-order streams (4th and higher) and 200 m
interval for the lower order streams (3rd and lower). This method
was followed to target equivalent representation of all streams, as the lower
order streams often did not extend more than 500 m in length (Sharma et al.
2021). In total, 38.92 km of river stretch was sampled with a total of 51
sampling points spanning across the Bhagirathi River and three of its major
tributaries Kakori, Jalandhari,
and Sian using cast nets for fishes and D-frame dip net for
macroinvertebrates. The catch per unit effort (CPUE) of the cast net was
calculated by dividing the catch of each sampling site by the number of hours
fished (Morgan & Burgess 2005). The fishes were caught and released
post-sampling. The water quality parameters were recorded using a
multi-parameter water monitoring kit, while the microhabitat characterization
was done based on Bain & Stevenson (1999).
Results
Camera trapping effort (78,828
trap nights) across the basin resulted in 28,257 captures of different mammal
species. Excluding Eurasian Otter, a total of 39 species of mammals were
recorded during the survey belonging to 13 families in five orders (Pal et al.
2020). A solitary otter was likely first photo-captured on 25 September
2018 at 1352 h, although the species could not be definitively identified as
the capture was too close to the camera. Another photo of an individual was
captured on 14 February 2019 at 0546 h (Image 2). Based on the characteristic
features such as the conical tail, lighter underside, the bare and black
rhinarium with a W-shaped upper margin, the otter species was confirmed as the
Eurasian Otter (Hussain 2013; Menon 2014). Along with photographic capture we
also captured a 30-sec video recording, where the otter was observed moving on
snow. The species is known to survive in extreme cold conditions and has
previously been reported at an elevation of 3,700 m in the Himalaya (Prater 1971) and up to 4,120 m in Tibet (Mason &
Macdonald 1986).
An image of the Eurasian Otter
was captured near the Dabrani region, which is the
confluence point of Jaulighad, and Songhad tributaries with Bhagirathi River. It was captured
at an elevation of 2,700 m near the bank of Jualighad
approximately two km away from its confluence with the main river. The area
is characterized by highly rugged mountainous terrain (Image 2). The river
forms a deep constricted V-shaped valley in Dabrani
together with a high runoff and steep gradient. The area where the otter was
captured is characterized by big rocks, boulder fields, and deep crevices. Such
habitats are considered as ideal denning and breeding sites for the Eurasian
Otters (Hussain 2013). Dense bankside vegetation is also an important
determinant of otter’s presence as crucial resting sites (Kruuk
2006). The vegetation in the area where otter was photocaptured
is a dense temperate riverine habitat with steep slopes covered with conifer-
broadleaved mixed forests characterized by the presence of tree species such
as Alnus nepalensis, Betula
alnoides, and Cedrus
deodara. The habitat in the upstream river
changes to sub-alpine where species such as Rhododendron sp. and Pinus
wallichiana are found. Other mammals
recorded from the same location are common leopard, Himalayan Goral Nemorhaedus goral, Himalayan Tahr Hemitragus jemlahicus, Himalayan Serow Capricornis thar,
Himalayan Langur Semnopithecus schistaceus, and Yellow-throated Marten Martes flavigula.
Adapted for a semi-aquatic life,
Eurasian Otters are primarily piscivorous with fish contributing 80% of their
diet (Webb 1975; Ruiz-Olmo & Palazon
1997). Throughout our surveys we found the exotic Brown Trout Salmo trutta to be the only fish species inhabiting
elevations above 2,500 m, with a CPUE of 1.02 kg h–1 ranging between
0.22 to 2.65 kg hr-1 across all the sampling locations. As accounted
for in our surveys, the high elevation streams (>2,500 m) of Bhagirathi
Basin comprise 26 families of macroinvertebrates most of which belong to the
Order Trichoptera, which is considered as a major
diet of the Brown Trout (Fochetti et al. 2003). This
underscores a habitat rich in diet for sustenance of the Brown Trout, which in
turn could be a potential food source for the Eurasian Otter in the high
elevation river stretches. The aquatic
habitat in the high-elevation basin was characterized with dissolved oxygen
(8.65±0.59 mg/l) and total dissolved solids (44.72±20.02 ppm) with a low water
temperature (7.55±3.09 °C) across the sampling duration supporting the
sustenance of Brown Trout. The water flow was recorded to be swift across the
width of the river ranging between 1.5 to 4.4 ms-1 with a
microhabitat predominantly defined by fast flowing cascades, runs and rapids.
Further, the Eurasian Otters are known to move large distances (adult male:
38.8±23.4; adult female: 18.7±3.5 km) (Durbin 1998; Green et al. 1984; Kruuk et al. 1993; Kruuk 1995)
along the length of the river (which possibly include lower elevations). As
such, other studies documenting the presence of fish species such as Pseudecheneis sulcata,
Tor tor, Schizothorax
richardsonii, Opsarius bendelisis and loaches of the genus Schistura
possibly indicate a rich ichthyofaunal diet for the Eurasian Otter (Rajvanshi et at. 2012). It thus makes it evident that the
potential food available for Eurasian Otter has been identified along the
stretches of Bhagirathi River and necessitates the need for more surveys to
document Eurasian Otters in the Himalayan region.
Discussion
In a four year effort, Otters
were recorded only twice. Although a large network of camera traps was used in
the study, very few were deployed near rivers or streams. Of 318 cameras
deployed in the basin, only five cameras placed within 1 km distance from the
river or stream. Otters may have been present in deep gorge areas, but as the
sites were inaccessible they could not be sampled. Otter presence often goes
unnoticed because of their elusive, solitary, and nocturnal habits. We
recommend more dedicated surveys using camera traps to understand the status
and distribution of Eurasian Otter in the region. A large chain of tributaries
supports Bhagirathi; most of them are still in pristine conditions.
Additionally, their presence should be explored in the similar habitat in other
catchments of Uttarakhand. There is an urgent need to understand the scattered
population of Eurasian Otter in order to effectively protect this species.
Removal of bank side-vegetation, construction of dams, draining of wetlands,
aquaculture, and associated human-made impacts are some of the potential
threats to Eurasian Otters (Roos et al. 2015). Dams have further been
implicated in the decline of the Eurasian Otter (Foster-Turley et al. 1990;
Macdonald & Mason 1994).
Currently the Bhagirathi River is
dammed at 11 locations (Image 1), which has changed the hydro geomorphology of
the river. The river has been altered drastically from a swiftly flowing
stretch (due to steep gradient) into a vast stretch of semi stagnant water with
a characteristic flat gradient and large volumes of water (Agarwal et al.
2018). Fish diversity in Bhagirathi River is also currently declining and is
threatened by blockage of migration routes, disconnection of the river and
floodplain, changes in flow regime, change in physiochemical attributes
(Agarwal et al. 2018). Destructive fishing practices in the lower order
tributaries of the Bhagirathi, which are potential spawning grounds and nursery
sites for many cold-water fish, are risking the viability of the fish
populations imperative for the otter’s diet. In addition to the existing
pressures on the aquatic ecosystem, there are four more dams commissioned, one
under construction and one proposed hydropower project in Bhagirathi River,
which will potentially affect 70% of river length (Chopra et al. 2014). While
mitigation strategies are currently being adapted to reduce impact on fish,
otter presence further necessitates targeted management for the high-altitude
Himalayan rivers. Mitigation strategies need to be revised to include a wider
range of flora & fauna and consider the impact on the riparian ecosystem.
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