Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 January 2022 | 14(1): 20469–20477
ISSN 0974-7907
(Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.7477.14.1.20469-20477
#7477 | Received 30
May 2021 | Final received 20 November 2021 | Finally accepted 26 December 2021
Population, distribution and diet
composition of Smooth-coated Otter Lutrogale
perspicillata Geoffroy, 1826 in Hosur and
Dharmapuri Forest Divisions, India
Nagarajan Baskaran 1,
Raman Sivaraj Sundarraj
2 & Raveendranathanpillai
Sanil 3
1 Asian Nature Conservation
Foundation, Centre for Ecological Sciences, Indian Institute of Science,
Bengaluru, Karnataka 560012, India.
1 Present Address: Department of
Zoology & Wildlife Biology, A.V.C. College (Autonomous), Mannampandal, Mayiladuthurai, Tamil Nadu 609305, India.
2,3 Department of Zoology &
Wildlife Biology, Government Arts College, Udhagamandalam, Tamil Nadu 643002,
India.
1 nagarajan.baskaran@gmail.com
(corresponding author), 2 ottersundar@gmail.com, 3 sanilravi@gmail.com
Editor: Nicole Duplaix, Oregon State University, Corvallis, USA. Date of publication: 26 January 2022
(online & print)
Citation: Baskaran, N., R.S. Sundarraj & R. Sanil (2022). Population, distribution and diet
composition of Smooth-coated Otter Lutrogale perspicillata Geoffroy, 1826 in Hosur and Dharmapuri Forest
Divisions, India. Journal of Threatened Taxa 14(1): 20469–20477. https://doi.org/10.11609/jott.7477.14.1.20469-20477
Copyright: © Baskaran et al. 2022. 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: Asian
Nature Conservation Foundation, C/o. Centre for Ecological Sciences, Indian Institute of Science, Bangalore and Kenneth Anderson Nature Society, Hosur,
Tamil Nadu.
Competing interests: The authors
declare no competing interests.
Author details: Nagarajan Baskaran, Assistant Professor, teaching
MSc Wildlife Biology and BSc Zoology at the Dept. of Zoology & Wildlife
Biology, A.V.C. College (Autonomous). Research interest-—mammalian behavioural ecology.
Studying Asian Elephants since 1990 in the Eastern, and Western Ghats and Eastern
Himalayas. Member of IUCN-SSC Asian Elephant Specialist Group since 2002. Raman
Sivaraj Sundarraj—a guest
lecturer at the Dept. of Zoology & Wildlife Biology, Govt. Arts College,
Udhagamandalam. Teaching BSc & MSc Wildlife Biology. Research
Interest—entomology. Raveendranathanpillai
Sanil—Associate Professor at the Dept. of Zoology
& Wildlife Biology, Govt. Arts College, Udhagamandalam. Teaching BSc &
MSc Zoology. Research Interest—molecular biology & bio-chemistry.
Author contributions: NB—conceiving the concept,
planning & execution, data analysis & writing. RSS—data collection,
entry & preliminary analysis. RS—helping in data analysis & writing.
Acknowledgements: We are grateful to the Tamil
Nadu Forest Department for permitting this study and the Asian Nature
Conservation Foundation (ANCF) for funding. We also thank Mr. K.G. Avinash, GIS Expert, ANCF in helping us to produce the
distribution maps.
Abstract: Living in different aquatic
ecosystems, otters play a vital role in maintaining aquatic species
assemblages, particularly fish communities. Thus their wellbeing indicates the
health of wetland ecosystems. Smooth-coated Otter Lutrogale
perspicillata, a piscivorous mustelid, is
widely distributed across Asia. Its population is declining due to habitat
transformation, pollution and hunting. This
study aimed to understand the ecological requirements of the species by assessing
its distribution and its determinants, population and diet composition along the Cauvery River in Hosur and Dharmapuri
Forest Divisions. Through monthly
extensive surveys between December 2010 and February 2011, covering 62.5 km of
Cauvery from the Karnataka border to Palar River
junction, this study identified and mapped a 31 km stretch from Dubguli (Yellolapatti) to Biligundlu (Musulumaduvu) as an otter distribution area. Comparison
of ecological parameters including bank type, water depth, river width, human
disturbance, vegetation cover and water current with the distribution pattern
of otters across 125 blocks revealed that water depth and vegetation cover
influenced otter distribution positively, while human disturbance had negative
influence (these three variables explained 54% of variation in otter
distribution). Based on direct sightings, seven different groups consisting of
36 individuals were estimated as the minimum population. The mean group size
was 3.8 ± 0.16 (range: 2–7) individuals. Twenty-one otter spraints were
analyzed to determine diet composition, revealing that otters feed on insects, molluscs, crabs, fish, frogs, reptiles and birds. Fish
constituted the bulk of otter diets. Conservation measures like reducing
anthropogenic pressures (e.g., fishing, cattle pens, tourism), increasing
awareness of sustainable fishing to stakeholders, and instituting long-term
monitoring programs are suggested for the long-term conservation of otters in
the study area.
Keywords:
Carnivora, Cauvery River, determinants, diet, group size, Hosur and
Dharmapuri Forest Divisions, Mustelidae, population,
water depth influence.
INTRODUCTION
Otters are piscivorous mustelids
belonging to the family Mustelidae and subfamily Lutrinae. Of the five species of otters found in Asia,
three occur in India: the Smooth-coated Otter Lutrogale
perspicillata (Image 1), the Eurasian Otter Lutra lutra, and
the Oriental Small-clawed Otter Aonyx cinerea (Hussain 1993; Prater 1998; Reuther 1999; Menon
2003; Raha & Hussain 2016). The Smooth-coated
Otter is distributed widely throughout India south of the Himalaya (Pocock
1949; Prater 1971; Hussain 1993) and also in Myanmar, Indonesia, Kampuchea,
Laos, Malaysia, Vietnam, southwestern China, and Brunei, with an isolated
subspecies, L. perspicillata maxwelli,
found in the marshes of southern Iraq (Mason & Macdonald 1986).
Living in different aquatic
ecosystems (Pardini 1998), otters play a major role
in maintaining aquatic species communities, particularly fish communities (Sivasothi 1995; Anoop & Hussain 2005). They are health
indicators of wetland ecosystems, being sensitive to degradation of habitat and
the food chain (Erlinge 1972). Loss of wetlands
habitat, reduction in prey species, disturbances from developmental projects
and poaching are the major threats to otter survival in India (Nagulu et al. 1999a,b; Meena 2002). The Smooth-coated Otter
is presently listed as a ‘Vulnerable’ species on the IUCN Red List (de Silva et
al. 2015), Appendix I in CITES (CoP 2019) and is
protected under Schedule II in Indian Wildlife (Protection) Act (1972). Despite
their wide distribution and vital role in the wetland ecosystem, not much
attention has been paid to understand their ecology. The existing populations
of the species and their habitat have never been systematically surveyed
throughout India (Hussain & Choudhury 1997). Systematic data on their
habitat, distribution, population, and feeding ecology are essential for
conservation planning and management of the species in India.
In southern India, the species
has been studied in Periyar Tiger Reserve, Kerala
(Anoop 2001; Anoop & Hussain 2005) and in the Cauvery River in Karnataka
(Shenoy 2005; Shenoy et al. 2006), in particular the Cauvery Wildlife
Sanctuary. This study aimed to cover the entire range of the species in Cauvery
River to evaluate the current distribution, population, group size, and
diet.
Study Area
The study was carried out along
the Cauvery River within Hosur and Dharmapuri Forest Divisions, stretching from
Ichiebara (12.198 N, 77.593 E) to the junction of Palar (11.953 N, 77.676 E), a tributary of the Cauvery
(Image 2) between December 2010 and August 2011. The river stretches over 62 km
and varies in altitude from 307 m upstream to 236 m downstream. Cauvery is a
major perennial river, the eighth largest river of the subcontinent and ranks
as a medium river on the global scale (Jayaram 2000). It provides water to most
areas in Karnataka and Tamil Nadu states. The Cauvery originates at Talakaveri (12.198 N, 77.593 E) in Kodagu district of
Karnataka in the Western Ghats at an altitude of 1,341 m. From the edge of the
Western Ghats, within sight of the Arabian Sea, to the Bay of Bengal, the river
traverses through nearly 770 km in a roughly north-west to south-east direction.
It passes through the Western Ghats, the Deccan Plateau and the Eastern Ghats,
crossing diverse habitats ranging from high altitude shola forests to the dry
scrub jungles of the plains (Jayaram 2000). It has 29 major tributaries and its
basin receives rainfall from the south-west and north-east monsoons with a
major share from south-west monsoon. The river basin in the study area provides
natural habitat to a diverse highly threatened mammalian species. The riparian
habitat offers an important habitat to the Smooth-coated Otter (Baskaran et al.
2010). The river basin and its adjoining areas in Hosur-Dharmapuri Forest
Divisions are subject to severe anthropogenic pressure in terms of cattle
grazing, MFP collection, fishing, tourism, and pilgrimage.
MATERIALS AND METHODS
Mapping of otter habitats
To map the distribution of otter
and its habitats, the 62.5 km of the Cauvery River falling within the study
area was marked into 125 survey blocks of 500 m and surveyed by foot on a
monthly basis from December 2010 to February 2011. During each survey, the
presence or absence of otters based on direct sightings and indirect evidence
was recorded in each block. All approachable islands within the river were also
surveyed. The indirect evidences considered for their presence include spraints
(fecal matter), tracks, holts, food remains, and scrapes (Ottino
& Giller 2004). Spraints were categorized
according to consistency and degree of bleaching, they were considered fresh
when found with moisture and strong odour, old when
intact but without moisture and odour, and very old
if disintegrated without moisture and odour. The
tracks, holts and food remains were divided into three different categories
based on moisture, appearance (disturbed/undisturbed), condition in case of
food remains (fresh/old/very old) and when found with spraints their status was
taken into account for categorization. At every sighting of otters and their
evidence, the geographical location (latitude and longitude) and the survey
block number were noted down using a global positioning system (GPS).
Superimposing the otter location geocoordinate into Google Earth map, we
established the otter distribution map.
Assessment of factors influencing
distribution
Studies on otters (Hussain & Chodhury 1997; Ottino & Giller 2004; Anoop & Hussain 2005; Shenoy et al. 2006)
show that variables such as river bank type (earthen, sandy, and rocky) river
width, water depth, water current (low and high), vegetation density and human
disturbance influence the distribution pattern of otters. The human disturbance
was rated as low for areas with infrequent disturbance by local people due to
fuel wood and MFP collection, bathing and cattle grazing, medium for areas with
frequent disturbance by local people due to fuel wood, MFP collection,
self-fishing, fire for cooking, bathing, cattle grazing and eco-tourism, and
high for areas with regular disturbance by local people due to fuel wood
collection, self/commercial fishing, MFP collection, bathing, cattle grazing and
cattle pen, tourism including seasonal pilgrimage, fire for cooking, and
discarded food. These variables were evaluated at each 500-m interval in the
survey blocks. At each survey block, the river width, water depth and water
current were evaluated at three to five locations and averaged for each block.
Within each survey block, vegetation density was assessed at 100-m intervals,
placing a 20 m2 quadrat for trees, 5 m2 quadrat shrubs,
and 1 m2 quadrat for grass species and averaged for each block. The
difference in otter abundance observed among (like river bank type: earthen,
sandy, rocky) and between categories in different variables (like water
current: low and high) were tested for statistical significance, respectively,
employing, Kruskal-Wallis H test and Mann-Whitney U-test in SPSS Version 16.0.
The influence of ecological
factors on the distribution of otters was explored using multiple regression
analysis after testing for normality. In the multiple regression framework, the
dependent variable was the otter abundance, arrived based on both direct
sighting of otter and their indirect evidences, while the independent variables
were the river bank type (earthen, sandy, and rocky), river width, water depth,
water current, vegetation density and human disturbance. At first the
relationship between the dependent variable and independent variables were
tested using scatter plots. Based on the relationship of independent variables,
the variable was entered either in linear form or non-linear form with quadratic
term. When the relationship was quadratic, both independent variable and its
square term were entered into the multiple regression models. If the quadratic
term turned out to be insignificant, it was dropped. At the end, only
significant independent variables were retained in the equation.
Evaluation of population and
group size
Although the presence or absence
of otters could be assessed through direct sighting of otters and their
evidence, no simple foolproof method is available for censusing river otters (Melquist & Dronkert 1987). A
number of factors influence marking intensity and hence this measure cannot be
used as a direct indicator of population size (Jefferies 1966; Krqsuuk & Conroy 1987). The Smooth-coated Otter lives
in social groups that vary in size and change with seasons (Hussain 1996; Anoop
& Hussain 2005). The population size was estimated based on the spatial
distribution of various groups, differentiated based on group size and their
movement pattern observed during the study period. In total, seven different
groups were differentiated based on group size and movement pattern and the
total number of individuals recorded within each group was taken into account
to estimate the population size in the study area. Data on group size were
recorded on each sighting of the identified groups. Mean group size was
estimated for the seven groups we identified by averaging the groups size
recorded in the multiple sightings of the respective groups. Similarly, the
mean group size for overall population was arrived averaging the group size of
all the seven groups.
Diet composition
Spraint collection: To study the diet composition of
Smooth-coater Otters, spraint analysis was used following Anoop & Hussain
(2005), as direct observation was not possible due to anthropogenic
disturbance. Spraints of the otter were collected visiting the riparian habitat
on fortnight interval. Spraints were collected in self-lock polythene covers
and labeled with different variables such as status of the spraint, microhabitat,
date, and location. The collected samples were air-dried at room temperature
and stored separately for laboratory analysis.
Reference
sample of fish collection: To identify the fish species from the spraint, a checklist of fish
presents in the Cauvery River was prepared. Different fish species were caught
from each survey block using a gas net. The fish species were identified
using standard reference books (Jayaram 1994) with the help of experts from the
Indian Institute of Science, Bengaluru. From each species, a set of scales were
collected and permanent reference slides prepared by mounting with a drop of
glycerin and seal with adhesive.
Spraint
analysis: The air-dried
spraints were weighed to nearest 0.01 g using a physical balance. From each
spraint, mucus was removed soaking it in a solution of oxidizing agent (Webb
1976). The spraint was washed with a sieve of 0.5 mm mesh and dried again. All
prey remains were segregated under a binocular microscope, assigned to food
categories and weighed. Species level identification of the fish were done
using reference slides. Other species like insects, mussels, crabs, amphibians,
reptiles, and birds were broadly segregated into order level using feathers,
teeth and other bones, insect remains, shells, etc. The buff white colour of the bone was used to identify the frogs eaten by
otters, while in the case of crab and mussel, general shape, colour and shape exoskeleton were used as key (Anoop &
Hussain 2005). The segregated food categories were air-dried and weighed using
a physical balance.
Data are
presented for each food category using three different methods: (i) Percent frequency F= number of spraints containing a
given prey category divided by total number of spraints × 100 (Jenkins et al.
1979), (ii) Relative percentage frequency R= number of occurrences of a food
category divided by total number of occurrences of all prey categories × 100
(Rowe-Rowe 1977), and (iii) Dry weight Dw= dry weight
of a given food category divided by total dry weight of all prey categories ×
100.
RESULTS
Distribution
58 direct sightings and 31
indirect indications were recorded across 125 survey blocks in the Cauvery
River. Direct sightings and indirect evidence showed that otter distribution
was restricted to the stretch from Dubguli (Yellolapatti) to Biligundlu (Musulumaduvu) downstream (Image 3). The total length of
this stretch is 31 km within this study area, no sighting or evidence of otters
was found between Anchetty stream to Uganium (around 6 km). Further, there was no direct
sighting or indirect evidence of otters in the rest of 31.5 km from Musulumaduvu to Palar indicating
restricted distribution of otter in the Hosur and Dharmapuri Forest
Divisions.
Factors influencing distribution
Otter were observed to be
significantly concentrated in river stretches with higher water depth (K-W χ2= 11.358, df= 2, P <0.01), in islands with
shrub/grass cover (K-W χ2= 40.595, df= 2, P <0.001), and in areas with lower
water current (M–W U=1098, P <0.05) and
human disturbance (K-W χ2- 33.379, df= 2, P <0.001) (Table 1). Further
comparison of otter abundance recorded in the five blocks with the ecological
factors prevailed in the respective block revealed that water depth (Coefficient±SE= 0.133 ± 0.034, P <0.001) and
vegetation cover (Coefficient±SE= 0.031 ± 0.005, P
<0.001) influenced the otter abundance positively, while the human
disturbance influenced negatively (Coefficient±SE=
-0.664 ± 0.190, P <0.01) and these three variables explained 54%
otter of the variations in distribution (Table 2).
Population and group size
The study, based on the group
size and spatial locations recorded from the 47 direct sightings,
differentiated seven different groups of otters. From these seven groups, the
study recorded a minimum of 36 individuals during the survey (Table 3). Out of
47 direct sightings of otters, the study estimated the mean group size of 3.8 ±
0.16. The minimum and maximum group size recorded was two and seven
individuals, respectively.
Diet composition
The analysis of 21 otter spraints
revealed that otters feed on prey items which include insects, molluscs, crabs, fish, frogs, reptiles, and birds. Fish
appeared most frequently in the diet of otters (Table 4). The fish species Labeo callbasu
occurred in 15 out of 21 scats, and also contributed 90% of dry weight of all the
food items, indicating importance of Labeo in
the otter diet in the study area. It is interesting to note that higher
vertebrates such as reptiles and birds seldom feature in the otter diet. In
terms of dry weight, fish accounted for 90% of otter diets (Table 4), followed
by birds (5%), frogs (2%), molluscs (1%), and crabs
(1%). Prey items such as insect and reptiles formed less than one percent of
the overall diet of otters.
DISCUSSION
Distribution of otter
This study identified 31 km of
otter habitat in the study area. The distribution of otter habitat was mapped
during the dry season, and it is likely that during the wet season otters may
expand their distribution area. Also, absence of otter signs in a particular
place does not necessarily mean otters are absent from the area, as
occasionally they may inhabit an area without depositing spraints (Jenkins
& Burrows 1980; Melquist & Hornocker 1983; Kruuk et al. 1987),
although this is infrequent (Chehebar 1985).
Nevertheless, the findings on the otter distribution area, mapped by the
present study, based on dry season observations, have vital management
implications, as it is a pinch period in which animals restrict themselves to
smaller areas due to resource limitations, which need to be protected from
human disturbance for the long-term conservation of the species.
Factors influencing distribution
The multiple regression analysis
revealed among the five ecological correlates tested, water depth, vegetation
cover influenced otter distribution positively, on the other hand, human
disturbance influenced negatively. The positive influence of vegetation cover
in the form of dense shrub/grass cover along river banks and islands on otter
distribution is likely due to the preference of such areas by otters for
excavating their holts, most of which were recorded in river stretches
associated with dense undergrowth. This has also been reported in earlier
findings (Shenoy 2002, 2005; Annob & Hussain
2005; Shenoy et al. 2006). Similarly, water depth also showed a positive
influence on otter distribution. Since the study period (December 2009–February
2010) was largely confined to the dry season, it is likely that during that
season otters in the study area preferred stretches with deep water to avoid
high temperatures. Also, Paterson & Whitfield (2000) reported that fish
distribution is closely correlated to water depth. It is important to note the
decrease in otter abundance with human disturbance through fishing, bathing,
cattle grazing, and forest product collection, which could affect the otter
distribution adversely. Direct observations of otters suggest bank edges with
sandy soil and islands of rocky outcrops and boulders provide ideal
microhabitats for feeding (Burton 1968; Channin
1985), sleeping (Channin 1985; Nolet
et al. 1993), grooming (Nolet et al. 1993), playing
(Shariff 1984), and territory marking (Green et al. 1984; Kruuk
1992). Islands and rocky outcrops in the middle of the river are safer for
aquatic species like otter to escape from threats as compared to river banks,
where anthropogenic disturbances are more and such islands are ideal if they
contain vegetation undergrowth to provide cover (Shenoy 2002). Prey
availability is probably a crucial factor influencing the distribution of the
otters follow their food abundance gradient and alter their home ranges
accordingly (Mason & Macdonald 1986). Our attempt to estimate the prey
abundance did not yield adequate data due to the reason that much of the river
stretches in the study area are with low water depth, which could not be
sampled using gill net. However, fish being the major prey of the Smooth-coated
Otters, fish must be available all the year round, if otters are to remain as
permanent residents in an area (Melquist & Hornocker 1983). Although, water depth, ground vegetation
and human disturbance explained 54% of the otter distribution in the study
area, the rest 46% could be a function of fish abundance, which is not
addressed adequately in this study.
Population and group size
Although no data is available
from southern region for comparison, a detailed survey on population conducted
along a 425-km stretch of the Chambal River in a sanctuary reports 29 otters
during 1988 and 14 in 1992 (Hussain & Choudhury 1997). The present report
of 36 otters for the entire stretch of 62 km surveyed (from Ichiebara
on the upstream of Cauvery River to the junction of Palar
in the downstream) represents a healthy population. Since the study covered the
Cauvery River stretch in the upstream only from Tamil Nadu boundary, it is
likely the same river further up in Karnataka region could also be supporting
Smooth-coated Otters and thus actual population may be larger than reported
here. Overall, the study estimates a mean group size of 3.9 individuals based on
47 sightings. The mean group size was marginally higher during February (4.3
individuals) compared to January (3.4 individuals). In National Chambal
Sanctuary, India, Hussain (1996) estimated a mean group size of 4.6 individuals
based on larger sample size (n= 422). The present finding of 3.9
individuals per group is comparable to those from Hussain (1996). The smaller
group size in the present study could be attributed to the short-term nature
representing only the dry season and the absence of wet season data in which
the group size reported to be larger (Hussain 1993).
Diet composition
Fish constituted the major prey
items during the study, both in terms of frequency of occurrence and dry
weight. When occurrence of a food item is high, that food is important for the
dependent species (Knudsen & Hale 1968). Similar to the present study, fish
were identified as the stable food of Smooth-coated Otters elsewhere in
southern India (Balasubramanian 1989; Anoop & Hussain 2005). Although the
otters are mainly piscivorous animals, in the present study area they also feed
on a variety of other prey items like insects, molluscans, crabs, reptiles,
frogs, and birds as reported elsewhere (Anoop & Hussain 2005). Similar to
the present study, Norris (1974) found the occurrence of freshwater mussels as
part of the otter diet. Otters rarely preyed on birds, although reported
elsewhere from other parts of India (Anoop & Hussain 2005). A similar trend
in diet composition has been reported for the Eurasian Otter Lutra lutra L. (Ottino & Giller 2004).
Conclusions
and recommendations
The study shows that
Smooth-coated Otters are distributed along the Cauvery River from Dubguli (Yellolapatti) upstream,
to Biligundlu (Musulumaduvu)
downstream. While water depth and vegetation cover influenced the otter
distribution positively, human disturbance influenced it negatively. The study
estimated 36 individuals as the minimum population of otter in the area and
showed that otters feed on insects, molluscs, crabs,
fishes, frogs, reptiles, and birds with fish as the principal component. As the
survival of otters depend on the fish population in the area, protection of
fish fauna of Cauvery River and the riverine system are essential for the
long-term conservation of the otters. Unfortunately, there is tremendous
pressure on fish fauna in the study area from local people due to commercial
fishing, which needs to be reduced to a sustainable level as the first step for
conservation of otters. Apart from fishing, the riparian habitats also
experience other kinds of anthropogenic pressure, including over grazing by
scrub cattle, cattle-pen and non-timber forest produce collections and
disturbances. Pollution from seasonal
pilgrimage and regular tourism as reported in Baskaran et al. (2010), which
should be regulated/ stopped for the conservation of riparian habitats of the
Cauvery River and its dependent species like smooth-coated otters. Increased
awareness of sustainable fishing by the community and long-term monitoring will
also benefit the otters’ survival.
Table 1. Distribution pattern of
smooth-coated otter in relation to ecological factors along Cauvery River in
Hosur and Dharmapuri Forest Divisions, Eastern Ghats.
Factor |
Category (n) |
Otter abundance mean ± se |
Kruskal–Wallis (χ2) / *Mann–Whitney U |
df |
P |
Bank type |
Earthen (37) |
0.41 ± 0.180 |
1.36 |
2 |
0.507 |
Sandy (45) |
0.84 ± 0.270 |
||||
Stony (43) |
0.51 ± 0.271 |
||||
Water depth |
Low (26) |
0.12 ± 0.085 |
11.358 |
2 |
0.003 |
Medium (58) |
0.40 ± 0.165 |
||||
High (41) |
1.20 ± 0.355 |
||||
River width |
Low (30) |
0.93 ± 0.437 |
0.715 |
2 |
0.699 |
Medium (65) |
0.58 ± 0.178 |
||||
High (30) |
0.30 ± 0.153 |
||||
Vegetation |
Low (17) |
0.0 |
40.595 |
2 |
0.000 |
Medium (59) |
0.0 |
||||
High (49) |
1.53 ± 0.329 |
||||
Water current |
Low (29) |
1.10 ± 0.410 |
*10.98 |
|
0.01 |
High (96) |
0.45 ± 0140 |
||||
Human disturbance |
Low (28) |
2.32 ± 0.520 |
33.379 |
2 |
0.000 |
Medium (57) |
0.18 ± 0.062 |
||||
High (40) |
0.0 |
Table 2. Regression equation
model to explore the influence of ecological factors on the distribution
pattern of Smooth-coated Otter along Cauvery River in Hosur and Dharmapuri
Forest Divisions, Eastern Ghats.
Variable |
Coefficient
± Std. error |
P |
model (R2) |
F |
model
(p) |
Constant |
0.348 ±
0.523 |
0.507 |
0.545 |
33.616 |
0.000 |
Water
depth |
0.133 ±
0.034 |
0.000 |
|||
Human
disturbance |
-0.664 ± 0.190 |
0.001 |
|||
Vegetation
cover |
0.031 ±
0.005 |
0.000 |
Table 3. Population size and
group size of Smooth-coated Otter estimated based on seven different groups
occupying the study area during December 2009–March 2010.
Group ID |
Survey blocks used |
Total number of individuals |
Group size mean ± SE |
1 |
12 to 15 |
5 |
4.0 ± 0.45 |
2 |
18 to 25 |
4 |
3.3 ±0.18 |
3 |
33 to 37 |
5 |
4.2 ± 0.37 |
4 |
45 to 49 |
5 |
3.7 ± 0.67 |
5 |
52 to 57 |
7 |
5.5 ± 0.96 |
6 |
62 to 68 |
5 |
3.5 ± 0.21 |
7 |
71 to 74 |
5 |
3.7 ± 0.33 |
Total |
12 to 74 |
36 |
3.8 ± 0.16 |
Table 4. Frequency of occurrence
of various prey items identified from Smooth-coated Otter spraints in the study
area December 2009–March 2010.
Prey items |
Occurrence |
Dry weight (%) |
|
Percent frequency |
Relative percent frequency |
||
Insects |
9.5 |
4.5 |
0.10 |
Molluscs |
9.5 |
4.5 |
1.12 |
Crab |
4.8 |
2.3 |
1.40 |
Pisces |
|
|
|
Labeo callbasu |
71.4 |
34.1 |
89.80 |
Channa argus |
9.5 |
4.5 |
|
Masatcembalus sp. |
14.3 |
6.8 |
|
Tor khudree |
9.5 |
4.5 |
|
Notopterus notopterus |
4.8 |
2.3 |
|
Unidentified fish |
33.3 |
15.9 |
|
Frog |
28.6 |
13.6 |
2.20 |
Reptile |
9.5 |
4.5 |
0.40 |
Birds |
4.8 |
2.3 |
4.70 |
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