Diversity of Snakes (Reptilia: Squamata) and Role of Environmental Factors in Their Distribution in Mizoram, Northeast India

Abstract

Survey on the fauna of snakes throughout Mizoram was made from 2007. Till the date, own field observation yields 49 species which represents almost 50% of the total species of snakes recorded from Northeast India. Out of the 5 families, occurrence is dominated by Colubridae (75.51%) followed by Elapidae (10.20%), Typhlopidae (6.12%), Viperidae (6.12%) and Boidae (2.04%). It is found that only 10 species are known to be deadly venomous. It is evident from the literatures that there is scanty information on the herpetofauna of Mizoram. Only few workers reported few species of snakes from the state. The present study provides the habitat, environment and altitudinal distribution of snakes encountered in Mizoram. Some of the present recorded specimens are rare species, new report for the state and rediscovered species from the country.

Full text

AEC-079
Diversity of Snakes (Reptilia: Squamata)
and Role of Environmental Factors in Their
Distribution in Mizoram, Northeast India
H.T. Lalremsanga1, Saipari Sailo2 and Chinliansiama1
1Department of Zoology, Mizoram University, Aizawl, Mizoram–796009, India
2Department of Environmental Science, North Eastern Hill University, Shillong, Meghalaya–764022, India
e-mail: htlrsa@yahoo.co.in,
Abstract—Survey on the fauna of snakes throughout
Mizoram was made from 2007. Till the date, own field
observation yields 49 species which represents almost 50%
of the total species of snakes recorded from Northeast
India. Out of the 5 families, occurrence is dominated by
Colubridae (75.51%) followed by Elapidae (10.20%),
Typhlopidae (6.12%), Viperidae (6.12%) and Boidae
(2.04%). It is found that only 10 species are known to be
deadly venomous. It is evident from the literatures that
there is scanty information on the herpetofauna of
Mizoram. Only few workers reported few species of
snakes from the state. The present study provides the
habitat, environment and altitudinal distribution of snakes
encountered in Mizoram. Some of the present recorded
specimens are rare species, new report for the state and
rediscovered species from the country.
Keywords: Snakes, diversity, Mizoram, Northeast India.
I. INTRODUCTION
Mizoram is a part of northeast India, an important
part of the Indo-Myanmar biodiversity hotspot, houses a
large number of flora and fauna. Mizoram with a total
geographical area of 21,081 km2 is situated in the
northeastern part of India between 21°56' - 24°31' N
Latitudes and 92°16' - 93°26' E Longitudes. The
elevation ranges from 40 m at Bairabi to 2157 m at
Phawngpui. There are 3 different seasons in Mizoram
namely the winter season (November to February),
spring (March to first part of May) and rainy season
(second part of May to October) [1]. Despite its
location, it is an area of global importance due to its
rich biodiversity, this region has remained poorly
explored, and all evidences suggest much of the
region’s biodiversity is being lost without even being
recorded [2]. Moreover, it is evident from the report
made by few workers that there is lack of information
on the herpetofauna of Mizoram. Among 3150 species
of snakes living on earth, 275 species are known from
India. So far, 102 species of snakes are recorded from
the northeast India [3]. From Mizoram, Pawar and
Birand reported 21 species [4], Harit and Ramanujam
reported 14 species [5], Mathew reported 38 [6] and our
own field observation yields 49 species excluding
subspecies which represents almost 50% of the total
species of northeast India. As it is mentioned by Marsh
et. al. that understanding patterns in the abundance and
distribution of animals is one of the major goals of
ecology [7], and also environmental variables are
known to influence species distribution in many ways
[8].This paper also deals with the influence of climatic,
ecological and topographical factors that reflects the
habitat of snakes throughout different seasons in the
state.
II. MATERIALS AND METHODS
A. Sampling Strategy
Extensive survey of snakes was made during day
and night throughout the forests, and aquatic habitats
such as streams, rivers, lakes, ponds, rice paddies,
ditches and pools in plantations by Visual Encounter
Surveys (VES) with the help of head lamps, torch light
and bamboo torch. All the 8 districts, Aizawl,
Champhai, Kolasib, Lawngtlai, Lunglei, Mamit, Saiha
and Serchhip were covered. The location
(latitudes/longitudes) and elevation of the surveyed
areas were observed with the help of Garmin (etrex)
Global Positioning System (GPS). The specimens were
photographed in their microhabitat, captured by using
snake hook or hand and kept in a bag or basket.
Altitudinal distributions above sea level (asl) are
categorized in to low elevation (<500 m), mid elevation
(>500 m and <1000 m), high elevation (>1000 m and
<1500 m) and extreme elevation (>1500 m).
B. Identification
After making careful observations, the collected
specimens were identified, morphometric and
meristematic measurements were taken and classified
using the published guides [9,10,11,12].
C. Preservation
Depending on the size of the collected material, 5-
10% formalin was used for preservation. The specimens
were catalogued and deposited in the departmental
museum of Zoology, Mizoram University. Tissue
samples were preserved in 100% alcohol for further
studies.

266  Advances in Environmental Chemistry
Abbreviations used in this paper are ALD =
altitudinal distribution; SEA = season in which the
species is encountered; W = winter season; S = spring
and R = rainy season.
III. RESULTS AND DISCUSSION
A. Snakes Recorded During the Present Work
From the present study, it was found that 49
species of snakes belonging to 5 families were recorded
from the different parts of Mizoram. Of these, 3 species
belonging to family Typhlopidae, 1 species under
family Boidae, 37 species under family Colubridae, 5
species of Elapidae and 3 species belonging to family
Viperidae.
B. Habitat, environment and altitudinal distribution
Most of the species were collected from Aizawl
district as the state capital Aizawl is the station and the
district covered all the categorized altitudes (Table).
TABLE 1: COLLECTION SITES, ALTITUDINAL DISTRIBUTION (ALD), SEASON IN WHICH THE SPECIES IS ENCOUNTERED (SEA), BEHAVIOR
AND HABITATS OF SNAKES RECORDED FROM MIZORAM DURING THE PRESENT INVESTIGATION (SINCE 2007 ONWARDS)
Districts ALD (m asl) SEA Behavior and Habitats
I.
1 Family Typhlopidae
Ramphotyphlops
brahminus
Champhai, Mamit 40-1650 R Likely to be seen under stones; come out after rains
2. Typhlops diardii Aizawl, Saiha 47-1205 R Nocturnal; burrowing
3. Typhlops jerdoni Aizawl, Champhai,
Kolasib, Mamit 40-1500 R Burrowing; come out after rains
II.
4. Family Boidae
Python molurus bivattatus Throughout the state 40-1450 S, R Crepuscular and nocturnal; rain-forests and grassland
III.
5. Family Colubridae
Ahaetulla prasina Aizawl, Mamit 60-2000 S,R,W Diurnal; arboreal
6. Amphiesma modestum Aizawl 897 R Diurnal, found among shrubs
7. Amphiesma stolatum Aizawl, Kolasib 46-890 R Diurnal; found in paddy field
8 Amphiesma xenura Aizawl 76-870 R Nocturnal;streams and ponds
9. Blythia reticulata Aizawl 895-1176 S, R Under logs and in decaying vegetation
10. Boiga cyanae Aizawl, Mamit 187-1245 R Nocturnal; arboreal
11. Boiga ochracea Throughout 50-1400 S,R,W Nocturnal; arboreal
12. Boiga quincunciata Aizawl 945 R Nocturnal; arboreal
13. Boiga siamensis Aizawl 854-920 R,W Nocturnal; arboreal
14. Calamariapavimentata Aizawl 875-926 S, W Nocturnal; terrestrial
15. Chrysopelea ornata Aizawl, Mamit 40-920 R, W Diurnal; arboreal
16. Coelognathu radiatus Throughout 50-1500 S,R,W Diurnal; terrestrial
17. Dendrelaphis cyanochloris Aizawl, Kolasib 46-1670 R Diurnal; arboreal
18. Dendrelaphis pictus Aizawl 40-1500 R Diurnal; arboreal
19. Enhydris sieboldii Mamit 56 S Active in the early morning; burrowing into mud
20. Liopeltis frenatus Aizawl 610-1830 R Diurnal; terrestrial
21. Liopeltis stoliczkae Aizawl 870-890 R Diurnal; terrestrial
22. Lycodon jara Aizawl, Mamit 40-870 R Nocturnal; terrestrial
23. Lycodon zawi Aizawl, Saiha 40-1200 S, R Nocturnal; mostly found near streams
24. Oligodon albocinctus Throughout 60-1500 S, R Crepuscular; under leaf litter, rocks, logs and loose soil
25. Oligodon cinereus Saiha 765 R, W Nocturnal; terrestrial
26. Oligodon cyclurus Mamit, Saiha 40-956 R Nocturnal; terrestrial
27. Oligodon dorsalis Aizawl 350-970 S, R Diurnal; terrestrial
28. Oreocryptophis porphyracea Aizawl, Serchhip 910-1200 R Crepuscular; terrestrial
29. Orthriophis taeniurus Aizawl 975 R Active by day and night; forest edges near water
30. Pareas monticolus Aizawl, Kolasib 300-910 S, R Crepuscular; found among leaves near water
31. Psammodynastes pulverulentus Aizawl, champhai 50-1583 S, R, W Diurnal; found in moist forest edges
32. Pseudoxenedon macrops Aizawl 470-890 R, W Diurnal; terrestrial
33. Ptyas korros Aizawl 40-2000 R Diurnal; terrestrial and arboreal
34. Ptyas mucosa Aizawl, Mamit 40-2100 R Diurnal; inhabitsopen forests
35. Rhabdophis himalayanus Mamit, Champhai 70-2000 R, W Diurnal; terrestrial
36. Rhabdophis subminiatus Throughout 50-1200 S,R,W Diurnal; terrestrial, forest marshy edges
37. Rhabdops bicolor Aizawl 175-975 R Diurnal; terrestrial
38. Rhadinophisprasina Aizawl 375-1200 R Diurnal; arboreal
39. Sibynophis collaris Aizawl, Kolasib 870-1500 R Probably active by day and night; montane
40. Sinonatrixpercarinata Aizawl 186 R Nocturnal; vegetation around water bodies
41. Xenochrophispiscator Throughout 40-975 R Active by day and night; in and around water bodies.
IV
42. Family Elapidae
Bungarus fasciatus Aizawl, Kolasib,
Mamit, Saiha 103-675 R Nocturnal; lives close to water
43. Bungarus niger Aizawl, Mamit,
Lungei 390-1250 R Nocturnal; terrestrial, prefer rocky places and leaf litter
44. Naja kaouthia Throughout 40-1500 S, R Nocturnal andcrepuscular; inhabit primary and secondary forests
45. Ophiophagus hannah Throughout 40-1500 S, R Diurnal; primary and second-dary forests close to water
46.
Sinomicrurus
macclellandi Aizawl, Kolasib 46-1030 S, R Nocturnal and crepuscular; hilly forested area
V.
47. Family Viperidae
Cryptelytrops erythrurus Throughout 40-1380 S,R,W Nocturnal; arboreal
48. Ovophis monticola Throughout 500-2000 S, R Nocturnal; terrestrial
49. Popeia popeiorum Aizawl, Mamit 340-1450 R Nocturnal; montane

Diversity of Snakes (Reptilia: Squamata) and Role of Environmental Factors in Their Distribution in Mizoram  267
Interestingly, species richness as well as abundance
is highly influenced by topography and altitudinal
gradients. Number of species recorded decreases as the
elevation gradients descended. High elevated cold
climatic condition do not favors the occurrence of lower
organisms which served as suitable foods for cold
blooded reptiles. The physical conditions of an
organism’s environment, temperature, light, moisture
and the food resources it contains primarily determine
the distribution of the organism in space and time [13].
Fig. 1: Species Richness against Elevation Gradients
It is indicated from the data that the appearance and
abundance of snakes during the study period was highly
influenced by the rainfall. This may be due to increase
in temperature (21oC to 31oC) at the onset of monsoon
rainfall which further triggered the appearance of their
prey (eg., frogs, lizards, birds, small mammals etc.).
Only few species were encountered during cold winter
(11oC to 23oC) where most of them undergone for
hibernation due to their poikilothermic activity.
C. New Records for the State
From the present survey, it was found that 14
species of snakes (Amphiesma modestum, Blythia
reticulata, Boiga cyanae, B. quincunciata, B. siamensis,
Calamaria pavimentata, Enhydris sieboldii, Liopeltis
frenatus, L. stoliczkae, Oligodon dorsalis, Orthriophis
taeniurus, Pareas monticolus, Sinonatrix percarinata and
Popeia popeiorum) are not recorded by earlier workers.
This provides new information on the extension range
of the above species in their distribution.
D. Rediscovered and Rare Species
Male and female specimens of Calamaria
pavimentata collected around Tanhril, Aizawl are the
only valid specimens of this snake throughout the
country. A single specimen of Enhydris sieboldii
captured from Langkaih river in the western part of
Mizoram is the only available specimen ever collected
from the whole northeastern India. The 3 specimens
ofLiopeltis stoliczkae collected from MZU campus are
an addition to the only 5 known specimens deposited in
the BMNH (Natural History Museum, London, Great
Britain) about 60 years ago. Other rare species includes
Python molurus bivattatus, Amphiesma xenura,
Lycodon zawi, Rhadinophis prasina, Bungarus niger,
Ophiophagus hannah and Sinomicrurus macclellandi.
E. Venomous Snakes
Out of these documented snakes, the venom of only
10 species, like 5 Elapidae (Bungarus fasciatus, B.
niger, Naja kaouthia, Ophiophagus hannah and
Sinomicrurus macclellandi), 3 Viperidae (Cryptelytrops
erythrurus, Ovophis monticola and Popeia popeiorum)
and 2 Colubrids (Rhabdophis subminiatusand R.
himalayanus) are known to be dangerous for human
while other colubrids, like Ahaetulla prasina, Boiga
cyanae, B. ochracea,B. quincunciata, B. siamensis and
Psammodynastes pulverulentus are provided with toxic
saliva which are mildly venomous.
IV. CONCLUSION
The present study revealed the current status on the
distribution of snakes ranging from very low to high
elevated level collected from different parts of all the
eight districts of Mizoram. Our own field observation
yields 49 species of snakes in Mizoram, of which 14
species are known to new records for the state. Out of
the 5 families, occurrence is dominated by Colubridae
(75.51%) followed by Elapidae (10.20%), Typhlopidae
(6.12%), Viperidae (6.12%) and Boidae (2.04%).
Besides the present records, additional8 species, like
Boiga gokool, B. multifasciata, B. trigonata, Lycodon
aulicus, Oigodon melanozonotus, Trachischium
monticolum, Trimerusus albolabris and Daboia russelli
were also reported by Mathew [6] without material
examined (except for Trimerusus albolabris with
museum no.V1/ERS/ZSI/9287 collected from
Bilkhawthlir, Kolasib district). Moreover, the
occurrence of reticulated python (Python reticulatus)
was confirmed from the skin moult retrieved from
Ngengpui river, Ngengpui WL Sin 1999 [4]. In future,
it is necessary to confirm the presence of the above
species in Mizoram as reported by other workers by
collecting in hand or documenting them with the help of
photographs. It is also indicated that the appearance and
presence of snakes is highly influenced by
environmental factors, like rainfall, temperature and
altitudinal variance that nourished their habitats in
terms of foods and shelters. Some species shows their
occurrence throughout the state is due to the fact that
those species with broad niches are expectedto be more
widespread because they may tolerate a greater variety
of habitat conditions [14]. The permission for collecting
the herpetofauna throughout Mizoram issued by the
Chief Wildlife Warden, department of Environment and
Forest, Govt. of Mizoram is acknowledged.

268  Advances in Environmental Chemistry
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