Hydrus enhydris Schneider, 1799 Historiae Amphibiorum, 1:245. Type locality: "Indiae orientalis;"
[Based upon an illustration of Mutta Pam in Russell, Indian Serpents, p. 35, pl. 30, 1796.]
Hydrus atrocaeruleus Shaw, 1802 General Zoology, 3:567, 1802 [Based upon
an illustration of Mutta Pam, in Russell, Indian
Serpents, p. 35, pl. 30, 1796.]
Enhydris caerulea Sonni and Latreille, 1801 Histoire naturelle des reptiles, 4:202,
1801 [Based upon an illustration of Mutta Pam in Russell, Indian Serpents, p. 35, pl. 30, 1796.]
Coluber pythonissa Daudin, 1803d Histoire naturelle…des
reptiles…de Buffon, rédigée par Sonnini, 7:202, [Based upon
an illustration of "Mutta Pam" Russell, Indian Serpents, p. 35, pl. 30,
1796.]
Homalopsis aer Boie, 1826b Isis von Oken, column 214. Type locality:
"Java." Holotype: Paris Museum. Collector: M. Oppel.
Potamophis lusingtonii Cantor, 1836 Transactions of the Medical
and Physical Society 7:139. Type locality: India.
Coluber aer - Eydoux and Gervais, 1837 Magasin de Zoologie Journal, 3, pl. 16, figures
2-3.
Homalopsis olivaceus Cantor, 1839 Proceedings of the
Zoological Society of London, p. 55. Type locality: Bengal. Holotype: based upon a
colored sketch in Bodleian Library.
Hypsirhina trilineata Gray, 1842 Zoological Miscellany p. 66. Type
locality: "China." Holotype: BMNH 1946.1.7.22. [The type is a female
with 21 scale rows at midbody. The bottle also bears the following information
“Ular Aer, Hypsirhina aer, India,
111.25.3.b.”]
Hypsirhina furcata Gray 1842 Zoological Miscellany, p. 66. Type
locality: "India." Syntypes: BMNH 1946.1.21.67-68. [The syntypes are
two neonates with 21 scale rows at midbody, and are un-remarkable.]
Hypsirhina bilineata Gray 1842 Zoological Miscellany, p. 66. Type
locality: "China." Holotype: BMNH 1946.1.5.31. [This is a male Enhydris enhydris with 21 scale rows at midbody.]
Hypsirhina aer - Gray 1849 Catalogue of the Specimens of Snakes in the
Collection of the British Museum, p. 72.
Homalopsis enhydris - Cantor, 1847 Catalogue Malay Reptiles, p. 99.
Hypsirhina enhydris - Duméril, Bibron,
and Duméril, 1854 Érpétologie
Générale...Reptiles, 7:946
Hypsirhina albolineata Morice, 1875c Coup d'Oeil sur la Fauna de
la Cochinchine Francaise, p. 58. Type locality: Vietnam. Syntypes: MHNL
42000343(2). The syntypes are two neonate specimens bleached white from light
and chemicals, both are females and have 21 scale rows at midbody.
Hypsirhina enhydris bilineata – Lampe
and Lindholm, 1902 Jahrbuch des Nassauischen Vereins für Naturkunde, 55:31.
Helicops indicus Annandale, 1905 Journal of the Asiatic Society of Bengal,
p. 211. Type locality: Bengal. Holotype: Calcutta Museum.
Enhydris enhydris - Barbour, 1912 Memoires of the Museum of
Comparative Zoology 44(1):122.
Etymology: Like the genus, this species is
named for its highly aquatic life style; enhydris
is Greek for water snake.
Common
Names: Wall
(1912) wrote about the history of the common names for this taxon.
Our
first introduction to H. enhydris is
through Russell who under the name "Mutta pam" figured and remarked
upon a specimen in 1796 which had been captured in an Eel trap in the Lake of
Ankapilly (North of the Godavery, near Vizagapatam). Three years later
Schneider alluded to it in his History of
Amphibians, under the name Hydrus
enhydris....Schneider's Water Snake suggests itself, reserving Russell's
name to designate the other common water snake alluded to by him and to which
Schneider also stands as godfather. I refer to Cerberus rhynchops....
The names mentioned by Russell are
the only ones known to me in India. These "Mutta pam," mud snake, and
"Ally pam" are presumably in use in the Vizagapatam District. In most
places in India I expect it would come under that very comprehensive title
"pani ka samp." Günther mentions "oular ayer" as the name
by which it is known to the natives in Java, and Flower says – ‘In Siam it is
called ‘Ngu‑pla’’ or fish snake, in common with other homalopsids.
Later, Wall (1924) called it
“Schneider's Water Snake.” Gharpurey (1944) undoubtedly drawing on Walls’
comments wrote, "On the east coast round about Vizagapatam it is called
Mutta pam or Ally pam, which means a mud snake." And, in his account he
calls it "Schneider's Water Snake." Whitaker (1978) reported its
English name in India as the “Common Smooth Water Snake.”
Das (1998) listed the common names
for this species in five different Indian languages. Assamese: Meni (=cow/buffalo [feminine], possibly
in allusion to innocence [for being non-venomous]. Bengali: Huria (=?); Kanametuli (=blind earth dweller); Paina shap (=water snake). Nepali: Mach giddhee (= fish brain). Tamil: Alai pambu (= surf snake); Mutta
pambu (=egg snake). Telugu: Ally pam
(=wave snake); Mutta pam (=egg
snake). These names were used in Russell’s Indian
Serpents p. 35, plate 30. Shrestha (2001) stated that “Dhod” is the common
name in Nepal. Hoesel (1959) reported that the English name for this species in
Java is “Fish Snapper”. And, Hindley (1988) called this snake the “Rainbow
Water Snake.”
Distribution
Enhydris
enhydris ranges from Nepal, northeast peninsular India and an apparent isolated
population in Sri Lanka, eastward throughout Bangladesh and Myanmar, across the
Indochinese peninsula, and southward into Indonesia from Sumatra to Sulawesi.
A discussion of questionable
localities follows. Its presence in Nepal was noted by Shrestha (2001), who
wrote, “It is common in the ponds, sluggish waters and the irrigated fields of
mountainous areas of Nepal.” I have not seen any specimens from Nepal to date
but its presence in lowland areas seems probable. Rooij (1917) and Haas (1950)
report this snake from New Guinea, these are most certainly misidentified Enhydris polylepis. Gyi (1970) does not mention Ceylon [=Sri Lanka] in his
distribution, but in his materials examined list stated that CAS 12767 is from
Ceylon with no specific locality. This supports Ambercrombie’s (1913) Jaffa
Province record, which Wall (1921) apparently over looked completely and it has
been over looked by more recent Sri Lankan herpetologists. My examination of
the Sri Lankan CAS specimen found it to be an unremarkable specimen of Enhydris enhydris. Several authors
(Sclater, 1891a, deRooj, 1917, Pope, 1935) state E. enhydris is in China.
Zhao and Adler (1993) have not listed it from China, noting that a Hong Kong
specimen was suspected of being from Thailand (Romer, 1961) and that recent
workers have failed to find it in Hong Kong (Karsen et al., 1986). Romer’s
comments were based upon BMNH 1956.1.12.93, a specimen apparently found on a
ship that had come from Bangkok. There was, however, a second Hong Kong
specimen (BMNH 56.11.17.58) presented to the BMNH by J. C. Bowring, and Wall
(1924) considered it present in China’s southern provinces and continental
islands. Additionally, the species is known to occur in North Vietnam, thus the
likelihood of its presence in tropical southern China cannot be easily dismissed.
Also of interest is its status in Laos, Deuve (1970) considered it present but
given the scale counts and illustrations his description of E. enhydris is based entirely on Enhydris subtaeniata (the sister species
to Enhydris enhydris, see the subtaeniata account). Thus, it may be
present in Laos and southern China but documentation is absent, similarly its
presence in Nepal and Sri Lanka are in need of further examination. Iskandar and Nio (1996) consider the Sulawesi population to be
introduced since it is found in the vicinity of just a few towns.
Diagnosis: A fresh water snake with 21 scale
rows at midbody; 153 - 174 ventral scales; a relatively long tail; a pattern of
longitudinal stripes, with no lateral or dorsal spots or bars; and a remarkably
small, narrow head. The internasal is single and contacts the loreal, and there
are two pairs of chin shields with the second pair longer than the first. The
snake that it may be most easily confused with is its sympatric (in the Mekong
drainage) sister species, Enhydris
subtaeniata. E. subtaeniata has
fewer than 153 ventral scales; a pattern of spots on scale rows 4 - 6; and two
or three pairs of chin shields, when there are two pairs the first pair is
longer than the second pair. Enhydris
bennettii also has 21 scale rows but its internasal does not make contact
with the loreal; the same is true for E.
chinensis which has 23 rows of scales at midbody. Enhydris jagorii, E. longicauda, E. innominata, and E.
chanardi also are sympatric with this species in the Indochinese peninsula
and all have 21 scale rows at midbody. However, these species lack a dorsal
pattern of longitudinal stripes, have fewer than 153 ventral scales, and have
extremely ovate, smooth scales lacking striations (enhydris and subtaeniata have
smooth scales with striations).
Size: The largest female measured had a
total length of 882 mm with a 148 mm tail. The largest male measured had a total
length of 700 mm and a 125 mm tail, both of these specimens came from the
vicinity of Kabin Buri, in eastern Thailand. Adult females tend to be larger
and more robust than males. There may be considerable size differences between
populations. The Ban Tha Hin, Lake Songkhla population in southern Thailand was
composed of snakes that were relatively small (n = 18 females, = 426, r = 375 - 509) compared to the few snakes obtained
at a site near Satun, Thailand. The population in Tonlé Sap, Cambodia contains
very large individuals overall (n = 32 females, = 538, r = 422 - 644), see Murphy et al. (2002). Karns
et al. (2005) reported on populations of E.
enhydris in central Thailand. The population at Ban Badan in the Khorat
Basin showed no sexual dimorphism in body size, while the coastal plain
population at Kabin Buri showed size sexual dimorphism. Literature comments about body size in this
species support the idea that body size varies between populations. In Java,
Hoesel (1959) considers its average length to be about 50 cm. Wall (1924)
reported a second-hand record from a Captain Frere in a private letter dated
July 1911; the snake was from Minbu, Burma and was said to be 972 mm (?total
length). Schleich and Kästle (2002) report females up to 96
cm and this length may be based upon Wall’s comment. Saint Girons (1972)
also reported an exceptionally large female (880 mm) from Tonlé Sap, Cambodia.
Based upon measurements of two litters (n = 15) born to snakes obtained in a
Bangkok market, neonates ranged in size from 143 - 162 mm SVL (= 155 mm).
This is about twice the size of the young reported by Batchelor (1958)
who stated neonates were about three inches (76.2 mm). Tails in males tend to
be longer than in females, but in some populations there is considerable
overlap, see Table 9. The smallest specimens measured were the syntypes of Hypsirhina albolineata that had SVLs of
131 and 133 mm with 39 and 40 mm tails respectively. Karns et al. (2005)
measured 47 neonates that were born in captivity, and had been held for several
days. All were from Kabin Buri, Thailand and had a mean SVL of 17.8 cm (r =
15.8-20.2) and a mean mass of 3.1 g (r = 2.7 - 5.0).
External Morphology
The head is small and slightly
depressed. The body is cylindrical to slightly depressed. The eyes are
dorsolateral, but slightly more lateral than some other species. The orbit
diameter is equal to, or greater than the width of the frontal.
On the head the rostral scale is
pentagonal and is about twice as wide as tall, it is
barely visible from above, and it and the other head scales are finely
tuberculate. The nasals are in contact; each having a diameter that is less
than the diameter of the eye, and the nasals are semi-divided with the cleft
touching to the first labial. The internasal is usually single, slightly penetrating
the nasals, and about twice as wide as long. The
prefrontal scales are in contact with the loreal and preocular; they are
slightly larger than the loreal, but less than the diameter of the eye. The
frontal is about twice as long as wide and about equal in length to the
parietal. The loreal is usually longer than tall and in contact with the first
three labials. The supraocular is single and the anterior portion is narrower
than the posterior portion; the preocular is single and taller than long; and
there are two postocular scales, with the bottom scale extending slightly under
the orbit. There are no subocular scales; the fourth upper labial enters the orbit.
The temporal formula is 1 + 2 + 3, and all temporal scales are just slightly
enlarged, the secondary and tertiary temporal scales are difficult to
distinguish from the occipitals. Upper labials number 7 - 8, usually eight.
On the chin lower labials number 9 -
10, usually 10 (Gyi gives a range of 10 - 12). The first three (rarely four)
are in contact with the anterior pair of chin shields. The second pair of chin
shields is longer than the first, but the first pair is broader than the second
pair. The second pair of chin shields is separated by a
small pair of scales. Two specimens from Myanmar and one specimen from Cambodia
have three chin shields on one side and two on the other. Males appear to have
more numerous tubercles on these scales than females. On females the tubercles
appear to be few and restricted to the margins of scales. Gular scales number 9
- 11.
On the body the dorsal scales on the
neck are in 23 - 27 rows. The highest scale counts (25 -27) on the neck come
from specimens on the eastern edge of the range (India and Myanmar). Striations
are present on the dorsal scales of this species and tubercles are present in
some males. Dorsal scales at midbody are in 21 rows, although four specimens (otherwise
unremarkable) from Myanmar have 23 rows. The scales are ovate and become only
elongate toward the midline and striations are present. Dorsal scales near the
vent are in 17 - 21 rows. They are ovate and become slightly more elongate
toward the midline, and they are striated. The ventral scales at anterior body
are about 2.5 times the height of a nearby dorsal, at midbody they are about
four times the height of a nearby dorsal scale, and at posterior body they are
about three times the height of a dorsal scale. Ventral scales number 153 - 174
in males and 153 - 170 in females, one aberrant specimen from Myanmar (KU
92480) has 126. The anal plate is divided and about the same length as the
preceding ventral.
On the tail the subcaudal scales are
divided and number 64 - 83 in males and 57 - 76 in females. Dorsal tail scales
are ovate and striated. Males have a slight constriction at the base of the
tail, and their tails are also longer than female tails. It is interesting to
note that when all populations are combined the subcaudal scale counts for
females overlap males. However, when individual populations are examined the
sexual dimorphism of higher counts in males becomes quite distinct in each population
examined. The notable exception being India. The Cambodia population has the
longest tails of the populations examined. At the base of the tail the width is
81% of the height, based on the average of five specimens.
Color and pattern. The head is a
uniform brown-gray with yellow upper labials. There is an indistinct nape
stripe. There is a dark stripe on the edge of the ventral scales and the first
scale row, most of the first scale row, all of the second, and the bottom part
of the third are yellow to cream. All scale rows above the third are dark
gray-brown. A dark mid-dorsal stripe is present in some specimens, on scale
rows 8 - 12. Other specimens may have a
red dorsolateral stripe on each side of the midline. The belly is usually cream with a faint midline
stripe and the edge stripes already noted. However, some specimens may have a
uniform red belly that extends onto the first two scale rows, and others may
have a dark blotch on each ventral scale. The ventral side of the tail has a
midline stripe and lateral stripes also. While examining large numbers of
specimens from southern Thailand, central Thailand, and Tonlé Sap, Cambodia it
became apparent that the Cambodia population showed the greatest diversity in
color and pattern.
Karyotype. Sharma et al. (1980)
reported a 2N chromosome number of 36.
Habitat
This highly aquatic snake uses a
variety of stagnant and slow moving aquatic habitats ranging from rice paddy,
canals, and ditches to lakes and rivers. It uses relatively shallow freshwater
environments with muddy substrates and can be found in and around urban areas,
it seems to thrive in disturbed habitats. I have found this snake dead on the
road next to drainage tiles containing water on university campuses in
metropolitan areas such as Bangkok and Khon Kaen Thailand, suggesting that it
occasionally leaves the water. This agrees well with the literature on this
species. Wall (1912) wrote, "...thoroughly aquatic in habit, as might be
inferred from the character, and position of its nostrils. It frequents rivers,
estuaries, lakes and marshy ground, even being found according to Cantor in
irrigated fields." However, Acharji and Mukherjee (1966) may have confused
this species with Cerberus when they
wrote, "It was found to feed on mud fishes which crawled on mudflats
during ebb tides." Laidlaw (1901) commented that one was found on Gunong
Inas (Malaysia) far from the river, it seems likely that it may have followed a
small stream to this locality, or was transported there by recent flooding.
Murphy et al. (1999) and Karns et
al. (2000) used trapping, radiotelemetry, and mark-recapture techniques to
study this species in a wetland on the edge of Lake Songkhla, Thailand. The wet
meadow was dominated by the aquatic grass Paspalum
vaginatum, and the study area contained numerous small pools, ditches and
canals, which included anthropogenic features including ditches and fish
enclosures. This species used edge habitat which was predominately the mud-root
tangle and its water interface at the edges of canals (39.2% of telemetric
locations) and fish enclosures (28.8% of telemetric locations). Other areas
used included wet meadow pools, lake shore, and ditches in the nearby town.
Daily movements were usually short distances (< 10 m), punctuated by longer
movements of distances up to 350 m over a 24 hour period. There was no significant
difference between the movements of males and females. Enhydris enhydris is a thermoconformer; it does not bask to raise
its body temperature. Instead it stays within the thermal envelope of the
environment, snake body temperatures stayed within the thermal minimums and
maximums of the microhabitats they use, and their body temperature showed
little variation from 30°C (Figure 3).
Neonates were rarely caught in traps; but they were found in the
mud-root tangle, near the water, but not at the mud-water interface where the
adults were commonly trapped. Use of this microhabitat by these small snakes
may allow them to avoid aquatic predators such as large fish.
The success of E. enhydris in disturbed environments and its more or less uniform
morphology across its broad geographic range suggest this species may have
expanded its range recently, and this expansion may have been assisted by
humans as they developed rice cultivation and sophisticated water management
systems to flood rice paddies.
Diet
and Feeding Behavior
Fish are the primary food of E. enhydris, and specimens examined
during this study contained only fish: Rasbora
sumatrana, Trichopsis vitta, and Trichogaster trichopterus (Murphy et al.,
1999; Voris and Murphy, 2002). In
central Thailand’s Kabin Buri area Karns et al. (2005) dissected 141 E. enhydris (63 males; 78 females) that
had died in gill nets as by-catch, 26 (22 females; 4 males) contained prey. All
stomach contents were fish, and two reproductive females contained food. The literature supports the piscivorous diet.
Mueller (1887) reported a fish, possibly Anabas,
from a specimen from Java. Saint Girons (1972) found only fishes in the
specimens he examined. And, Taylor and Elbele (1958) wrote, "The stomach
contained eight small fish and parts of others." Hoesel (1959) wrote it, “…is a skilled
catcher of fish, so it is often found amoung the catch of fish traps. In spite
of its nocturnal character, many are seen hunting the fish in full day-time.
Mostly it clings to some hold with its tail, the curved body in readiness for
snapping the passing fish.” Murphy et
al. (1999) reported that this species will sometimes seize fish larger than it
can swallow, and report one moving about 1.5 m with a three-spot gourami, Trichogaster trichopterus in its mouth.
Small fish are the usual prey, and it is not uncommon to find multiple prey
items in a single snake. Several specimens from Tonlé Sap, Cambodia contained
multiple specimens of a fish that appeared to belong to the genus Parambassis (Chandidae). The largest
fish take from an E. enhydris was an Anabas (Anabantidae) that was 17.3% of the snake’s mass.
Smith (1914b) wrote, “It appears to
subsist chiefly on fish, but Mr. Herbert informs me that he once caught one
which disgorged a skink Mabuia, a
very unusual meal, I should think, for this snake." Given the overwhelming
amount of evidence that this species feeds almost exclusively on fish the
presence of a lizard in its diet is highly questionable. In his 1943 book Smith
reported this lizard-eating as if it was his observation; it seems likely the
snake that contained the lizard was misidentified. However, there are sympatric
aquatic skinks (Tropidophorus) and it
is not impossible that they may be taken as prey.
Reproduction
Dates and observations for
copulation in homalopsid snakes are rare; there is an anecdotal account for
this species. Wall and Evans (1901) wrote about this species in Myanmar, “These
were discovered ‘in copula’ on the 16th November…they were in swampy
ground, some distance (about a quarter mile) from a creek, and three miles from
the Hlaing river, (tidal).” However, Wall (1912) later gave the date as 16
October 1899. Fishermen at Lake Songkhla in southern Thailand told us about
seeing this snake in “balls” at night, presumably referring to mating
aggregations, but the behavior was not verified.
St. Girons and Pfeffer (1971) and
St. Girons (1972) also reported on the Tonlé Sap, Cambodia population. Their
Table 1 and Figure 19 in the 1971 paper suggested two reproductive seasons per
year. According to this scenario females
are in vitellogenesis from early-December to mid-February, they carry out
gestation from mid-Feb to late April and parturition occurs in early May. During a second season, vitellogenesis occurs
from mid-June to mid-September, gestation occurs from mid-September to
mid-November, and parturition occurs in late-November.
One hundred and thirteen females
from three populations (Cambodia, Myanmar, and Thailand) were examined by
Murphy et al. (2002) for eggs and embryos. The Cambodia sample contained 32
females with (= 564 mm SVL) eggs or embryos 6 - 39 (= 20.3). Eight females from Myanmar (= 428 mm SVL) had 5 - 16 (= 7.8) eggs or embryos. Eighteen females from
Thailand (= 426mm SVL) had 5 - 16 eggs or embryos (= 8.1). On average the gravid females from
Cambodia were larger in body size, clutch size, and relative clutch mass than
female snakes from Thailand and Myanmar. And, clutch size was significantly
correlated with female body size. They hypothesized that the larger females and
clutch sizes in the Cambodian population were due to over-fishing of Tonlé Sap,
the source of the snakes. Over-fishing would have reduced the number of large
fish (potential snake and small fish predators) and allowed small fish (snake
prey) species to become more abundant. The smallest gravid female they reported
was 298 mm SVL.
Karns et al. (2005) found 25 of 78
(32.1%) females from Kabin Buri, Thailand in reproductive condition. The
average litter size was 11.0 (r = 2 - 20, n = 22). The mean gravid female was
56.8 mm (r = 43.6 - 69.8). The meanmass of gravid females was 164.5 g (r = 94 -
250.0). They found a significant relationship between female SVL and litter
size.
Some
populations of this species appear to have seasonal reproduction (Tonlé Sap,
Cambodia), while others appear to be totally aseasonal (central Thailand).
Thus, this species offers a unique opportunity to investigate how local conditions
impact reproduction. During the field studies at Lake Songkhla, Thailand many
snakes were handled, during data collection (in June and July). After females
had been handled, males that were picked up would often vibrate their bodies,
probably in response to the pheromones left by the females on the hands of the
researchers.
Predators
and Parasites
Stuart et al. (2000) found Enhydris enhydris composed about 80% of
the snake harvest at Tonlé Sap Cambodia. Six years later, Brooks et al. (this
volume) report that it is about 72% of the catch. While most of the snakes are
sold for crocodile food, gravid females of this species had their ova removed
for human consumption. This species is also exploited in southern Vietnam
(Stuart, 2004). Lilly (1993) reported this species was involved in the wildlife
trade in Indonesia. Liong (1954) described a captive Enhydris enhydris being eaten by the krait Bungarus candidus. Nandi (1984) observed a bandicoot rat, Bandicota inidca, seizing an Enhydris enhydris along a flooded roadside
ditch. Wall (1912) reported numerous nematodes in the stomach of a specimen
from Behar. Nematodes were abundant in the stomachs of virtually every Thailand
specimen examined. The Thai specimens often had so many worms that the specimen
appeared to contain prey, but when the stomach was examined, only a bolus of
worms was found. However, Cambodian specimens examined completely lacked the
worms.
Population and Abundance
This snake reaches spectacular
population densities in shallow, open wetlands with submergent-emergent
vegetation at such places as Lake Songkhla in southern Thailand, Kabin Buri in
eastern Thailand, and at Tonlé Sap, Cambodia. In these localities this species
dominates the aquatic snake assemblages with dense populations. The literature
comments cited in the habitat section of this account all suggest that this
species is relative common at certain locations and are similar to Cochran’s
(1930) impression that it is common in Bangkok. Murphy et al. (1999) marked a
total of 235 snakes with PIT tags near the village of Ban Tha Hin, on the edge
of Lake Songkhla, a Thailand study site. A total of 380 snakes were captured
with 144 recaptures. The results suggested 406 - 567 snakes were present on the
study site, and because these snakes use edge habitat they estimate that the
density was about one snake per two meters of shore line.
The localities that have dense
populations of this snake (Lake Songkhla, Thailand; Kabin Buri, Thailand; Tonlé
Sap, Cambodia) are lowland locations that have become freshwater habitats
relatively recently. Lake Songkhla was an ocean bay 200 years ago and it
undergoes salt water intrusions and is heavily fished. The other localities
were inundated with sea water within the last 6000 years and are also heavily
impacted by the fishing industry and other human activities. Thus it appears
that E. enhydris may be a disturbed
habitat/early successional stage specialist. It is entirely possible that as
aquatic ecosystems mature that these populations will undergo natural declines
and stabilize at a much lower level.
Venom
Apparently bites from this snake may
be a problem for humans. Acharji and Mukherjee (1966) stated that E. enhydris occasionally inflicts very
painful bites. And, D'Abreu (1912) described the following incident of a human
bite.
The subject, a healthy man of
about 36, while attempting to catch the snake, which had previously been
irritated, was bitten on the back of the right hand between the thumb and the
forefinger. There were two distinct punctures and the parts got inflamed at
once though scarcely two drops of blood were shed. Fifteen minutes later the
hand began to throb and the throbbing lasted for about an hour, after which no
ill effects were felt. The snake was a little over a foot in length, and the
place of occurrence was Parbatipur, Bengal.
Several hundreds of these snakes were
handled during our work at Lake Songkhla and Kabin Buri in Thailand and rarely
did they attempt to bite, and when they did there was no envenomation.
Natural History
Little is known about the habitat of this species. Most
of the specimens appear to have come from the immediate vicinity of Bangkok,
one of the largest and rapidly growing cities in Southeast Asia. Undoubtedly
much of its original habitat has been altered and its continued existence in
the city is problematical. However, Bangkok is built on a river delta, and it
still contains many canals that support fish, amphibian, and reptile
populations. Thus, its survival seems possible. USNM 83431 is a female with 13 well developed
embryos. All embryos are in Zehr’s stage 36 (hemipenes everted). The litter
weighs 39.0g.