Homalopsis plumbea Boie, 1827 Isis von Oken, column 560. Type locality:
Java. Holotype: RNHL 1163. Collector: Unknown.
Hypsirhina hardwickii Gray, 1835
2:187, Fig. 1 Illustrations of Indian Zoology. Holotype: BMNH 1946.1.2.44,
presented by Gen, Hardwicke. Type Locality: Penang. Collector: Unknown. [The
holotype has 19 - 19 - 18 dorsal scale rows, 125 ventral scales and 34
subcaudal scales and is a female. The chin shields are about equal in length.
These characters are consistent with other peninsular Malaysian specimens.]
Coluber plumbeus - Eydoux and
Gervais, 1837: 3, pl 16, fig 1.Magasin de Zoologie, Hypsirhina plumbea - Gray, Zoologica Miscellany,
p. 66.
Hypsicopus plumbea –
Fitzinger, 1843:25Systema Reptilium,
Eurostus plumbeus - Duméril, Bibron,
and Duméril, 1854, 7:955, pl. 84, Figure 2 Érpétologie Générale... Reptiles.
Enhydris plumbea - Stejneger,
1898: 12(3):222 Journal of the College of Science.
Etymology. The name plumbea is
probably derived from the Latin plumbeus meaning
“of lead.” This is most likely in reference to the dark gray dorsal coloration
found in many larger specimens of this species. Common Names: Yellow Bellied
Watersnake (Campden-Main, 1970); The Lead-Coloured Hypsirhina, Harwicke's
Hypsirhina, The Ular Aer (Gray, 1849); Hainanese name is “Pum-twa.” (Gressitt,
1940); “Mei Sa” (southeastern China)
(Gressitt, 1941); Mud Creeper (Hoesel, 1959); Lead Water Snake, Plumbeous Water
Snake (Reitinger, 1978); Olive Water Snake (Karsen et al., 1986); Common Rice
Paddy Snake, Water Snake (Kuntz, 1963); Boie’s Water Snake (Wall, 1924); Orange-Bellied
Mud Snake (Stuebing and Inger, 1999).
Distribution. This is a widely
distributed species ranging from the Andaman Islands (India) and Myanmar
eastward across the Indochinese Peninsula (including Laos) and southern China
southward into Indonesia. It is present on many, if not all, Indonesian islands
and extends its distribution eastward to Sulawesi. However, AMNH 3840 is said
to be from the Molucca Islands, if true this would extend the eastern edge of
the range. Saltwater may be a barrier for this species however, it occurs on
many Indonesian and Malaysian islands, and it may have reached these islands at
times of lower sea levels or its association with rice paddy may have allowed
it to spread with agricultural humans.
Also, elevation does not seem to be a serious barrier for this lowland
snake, in that it colonizes elevations to least 1200 m. Mell (1929b) found it
up to 700 m in Kwangtung, China; Smith (1943) obtained one at Bockor in the
Elephant Mountains of Cambodia at 3000 feet (914 m); and Deuve (1970) reported
it in Laos as reaching an altitude of 1200 m.
Diagnosis. A small snake with 19 scale rows at mid-body, 119 - 142
ventral scales, a small internasal scale that is isolated from the loreals, upper
labials 2 - 3 or 2 - 4 usually contact the loreal, and lower labials 1 - 4 contact
the anterior chin shields. Other homalopsids with 19 scale rows at mid-body are
Miralia. alternans and Raclitia indica. Of these species both
have a banded dorsal pattern, alternans
has lower labials 1 - 5 in contact with the anterior chin shield, and indica
has a ventral count in the range of 173 - 175.
Size. The largest individual of 91 specimens was a 713 mm female with a
63 mm tail from Kabin Buri, Thailand. The largest male had a total length of
473 mm and a 53 mm tail. Male tail/SVL ratios ranged from 0.12 - 0.19, the
range for females was 0.10 - 0.17. Bergman (1960) gave maximum length for males
as 420 mm with a 64 mm tail, and 426 mm for females with a 53 mm tail. Saint
Girons (1972) measured a 424 mm female, and a 298 mm male from the Cambodian population. Neonates are small; Pope (1935) reports a range of 122 - 160 mm.
External Morphology. The head is distinct from the neck and slightly
depressed. The body is cylindrical. The head shields of some males are
tuberculate (this may be a seasonal phenomenon). On the head the rostral scale is visible from
above, pentagonal, and broader than tall. The nasals are relatively large,
larger than the internasals or the prefrontals. They are usually semi-divided,
rarely completely divided. The cleft usually contacts a labial, but may also
contact the loreal or internasal. The internasal is single and not in contact
with the loreal. It has about the same area as one of the prefrontals, and
slightly penetrates the nasals. The pair of prefrontals makes contact with the
loreals. The frontal length is about the same as the interorbital distance, and
less than the eye-nostril distance. The parietals are about 1.5 times the
length of the frontal. The loreal is single, square, and in contact with the
second and third upper labials. The supraocular has a broad posterior margin and
a narrower anterior margin; the single preocular (rarely divided) is higher
than broad; postoculars number two; there are no subocular scales. The temporal
formula is 1 + 2 + 3. The upper labials number eight; the seventh is the
largest; the fourth, the fifth, or more often the fourth and fifth enter the
orbit. On the chin the lower labials number
9 - 11, usually 10 and the first 4 - 6 (usually the first five) contact the
anterior chin shields. The anterior chin shields are broader than the posterior
pair, but their lengths are variable from one population to another. A pair of
smaller scales separates the posterior pair; these may be tuberculate in some
males. The gulars number 2 - 5. On the body the dorsal scale rows number 19 - 19
- 17, but eight (8.8%) specimens showed 15 scale rows near the vent; and two
males from Sulawesi have 18 and 19 rows near the vent. The first row is ovate
and the scales become more elongated toward mid-body, all are smooth. However,
in males the dorsal scales in the first three rows, 5 - 6 scales anterior to
the vent, may have tubercles; also, the scales immediately lateral to the vent
may have tubercles. The anal plate is divided and slightly longer than the
preceding ventral. The ventral scales number 117 - 142 and do not show sexual
dimorphism in any of the populations examined, the ventral scales are 3 - 3.5
times the length of a nearby dorsal scale. On the tail the dorsal scales on the
tail are ovate, some on the midline are enlarged, and are similar to those
elsewhere on the body. The subcaudal
scales are paired and number 29 - 46.. The Vietnam, Thailand, mainland China,
and Taiwan populations show sexual dimorphism is the subcaudal counts, while
the Sabah population does not. At the base of the tail the width is 79% of the
height based upon an average of five specimens. Not included in the table are
three males from Sulawesi that had the highest subcaudal counts, 43 - 47.
Color and Pattern. The crown of the head is uniform gray, with the head
shields having a light colored margin. Scale rows 1 - 2 or 1 - 3 are the same
yellow-cream color as the belly. Scale rows above this are a uniform gray. The
ventral side of the tail has a midline, zigzag stripe. Older adults may be
uniform black, younger animals may be an olive green with black pigment on some
scales and pink, orange, or yellow patches on the face, particularly on the
labials. Thailand specimens tend to have a uniform gray pattern above dorsal
scale row three. The ventral pattern is uniform cream or yellow. All peninsular
Malaysia specimens examined show vertebral spots that are darker than the
surrounding pigment, their ventral scales have some pigment, and the midline of
the tail has a zigzag stripe. Vietnam specimens tend to be a uniform gray or
black above dorsal scale row three, and the belly tends to be uniform with the
exception of the zigzag stripe under the tail. Sabah (East Malaysia, Borneo)
specimens have a “net-like” pattern that results from each scale having a light
central spot. Vertebral spots are also present in some specimens. They also
have some scattered dark pigment toward the edge of each ventral, and a zigzag
stripe on the midline of the tail. Photographs of H. plumbea with several different color patterns are in field guides
and other publications. This species may have some ability to change color.
Habitat. This is an aquatic snake, but it is the most terrestrial of
the homalopsids studied to date based upon field observations. In Sabah, Voris
and Karns, (1996) found this snake associated with wet sites (wallows, marshes,
ditches, stream, pond banks) where it was most frequently found in the tangle
of roots and mud 10 - 20 cm below surface debris during the day and night. They
studied this animal in an old rice paddy that was being used as a water buffalo
pasture, with buffalo wallows. The snakes were concentrated around the edges of
these wallows and while they occasionally moved they were mostly sedentary.
Collection of this snake by hand required the destruction of its habitat by
pulling the mats of grass from around the edges of the wallows, thus they used
funnel traps. In southern Thailand the species was found in a wet meadow, and
was collected in funnel traps submerged along the shoreline (Murphy et al.,
1999). In northern Thailand it was collected in gill nets set in stagnant
ponds. In central Thailand it was hand collected at night by walking rice padi
dikes and examining shallow water and the mud substrate with a flashlight. It
occurs from sea level to at least 1200m (Deuve, 1970; Mell, 1922; Smith, 1943);
see comment in the Distribution section.
Other comments from
the literature describing this species habitat follow. Batchelor (1958) wrote,
"...at Asahan, seems to favor the padi sawahs, and the more overgrown,
sluggish ditches." Campden-Main (1970) said it is, "...almost
entirely aquatic...The species is particularly common in the rice paddies and
drainage ditches near Bien Hoa [Vietnam]. Several specimens crossing the road
through rice paddies at night were collected at Phan Rang [Vietnam]. Boulenger
(1903) quoted field notes from Annandale and Robinson who wrote, “Essentially
aquatic but often found under dead trees some distance from water.” Flower
(1899) found it, "...frequents freshwater-ponds or rivulets, but one I
found under a stone some little distance from any water." Karsen et al. (1986) stated, "An almost
totally aquatic lowland species found in sluggish or slow-flowing streams,
ponds and cultivated fields. Is predominantly nocturnal, emerging to forage for
food at night. In rainy weather may wander overland...Has been recorded from
few areas owing to its secretive habits but is expected to occur in many more
habits." Saint Girons (1972) found this species away from water in the dry
season, but notes that it prefers rice fields and marshland. Wall (1903)
commented, "All my specimens were caught in or about a sluggish stream
near our camp at Kowloon." Kuntz (1963) wrote about the Taiwan population,
“As the name implies, this snake is common to rice paddy and wet agricultural
areas, usually at lower altitudes. E.
plumbea is frequently found in the same habitat with Natrix [=Xenochrophis]
piscator. It is unusually active at night. On rainy nights it may migrate into
yards of homes near or adjacent to agricultural areas. E. plumbea has been found inside homes in Taipei and its
suburbs.” Pope (1935) wrote, "In
Fukien and on Hainan I failed to detect and marked differences between the
habitat preferences of plumbea and chinensis…” Museum material comes with
the following habitat information: “Kunai grass area, some brush”
(CAS-SU13688); “found in drainage ditch after heavy rain at night” (CAS144021);
“found in mountain agricultural area” (USNM 142508-12).
Diet and Feeding Behavior. Hypsiscopus
plumbea feeds on fish and amphibians, including amphibian larvae. Voris and
Karns (1996) examined 20 snakes caught by hand that contained food from a
population at Kayumadang, Sabah, Malaysia, 14 of these had identifiable remains
of amphibians, including an egg mass, three unidentifiable tadpoles, and ten
adult frogs. Four of the 10 frogs were the four-lined treefrog, Polypedates leucomystax (Family Rhacophoridae),
and six were unidentifiable as to species. Two snakes contained the walking
catfish, Claris teysmanni (Family
Clariidae). Snakes caught in traps were forced to regurgitate and produced
tadpoles less frequently than fish. Snakes maintained in captivity readily ate
fish and tadpoles. Additionally, a Sabah specimen (SSM REP0580b) not included
in Voris and Karns (1996) (325 mm SVL/47 mm tail, 37.4g female) contained an
8.0 g Rana [=Fejervarya] limnocharis (Family
Ranidae). Individuals in this population
fed both day and night. During the day the snakes fed on fish and tadpoles from
ambush sites in the mud-root tangle, at night they became active foragers.
Snakes that were using a nearby stream were more mobile than those using the
wallow microhabitats. Other literature supports its fish and frog-eating habits
across its distribution. Schmidt (1927) examined five Chinese specimens that
contained prey, three contained Rana and two contained Microhyla. Gressitt (1941) reported Rana [=Fejervarya] limnocharis, a fish, and a crustacean
from specimens from southeastern China. In Taiwan, Kuntz (1963) reported
"...its food consists of loaches and amphibians." In Hong Kong,
Karsen et al. (1986) found this snake to be "…an excellent scavenger,
consuming even decaying flesh. Diet includes frogs and fish." Pauwels and Lenglet (2003) reported the eel
like fish Macrognathgus siamensis
(Family Mastacembelidae) to the list of fish plumbea will feed on.
Pope (1929) hypothesized food partitioning between this species and Enhydris chinensis from a relatively
small sample of specimens, he wrote, "Examination of the stomachs has
shown that plumbea lives on an
amphibian diet, chinensis, a fish
diet. Seven stomachs of the present series of plumbea contained frog remains and the rest were empty or nearly
so, while fishes were found in the four chinensis
stomachs. These two snakes are enabled to inhabit the same fields through
avoidance of competition in feeding, one preying on fish, the other on
frogs." This hypothesis is not supported by more recent studies that show plumbea to have a diet composed of fish
and amphibians. Deuve’s (1970) assertion that plumbea feeds on mollusks; and Gressitt’s (1941) statement that it
feeds on crustaceans, are in need of further documentation.
Mori (1998) used captive neonate
and year-old plumbea to study prey
handling. Almost all of his observations
were made while the snakes were feeding underwater. He noted that neonates
frequently dropped prey and had to recapture it, and he found that they were
still dropping prey at the sixth feeding. Prey was always swallowed head first,
and prey-handling time increased with larger prey items. H. plumbea also used bilateral movement of the jaws followed by
neck-bending when swallowing prey. The larger the prey, the longer the snake
held it in its mouth before swallowing, envenomation was probably occurring
during this time.
Reproduction. Litter Size. For this study 19 gravid females from Taiwan
were examined. Snout-vent lengths ranged
from 282 - 480 mm, and they contained 2 -18 embryos (= 8.7). The RCM (n = 18) ranged from 0.064 - 0.596 (= 0.29). The effort per embryo
ranges from 0.307 - 1.770 (= 1.23). These litter sizes
mostly fall within the range of those reported elsewhere in the literature.
Schmidt (1927) reported 4 - 11 eggs in a “number of females from Hainan;"
Pope (1929) found eight females from China contained 2 - 9 eggs (= 5.9); Pope (1935) reported 2
- 11 young, (=
6), and stated birthing is over in August; Maki (1931) reported 10 - 15 young
from the Taiwan population; Taylor and Elbel (1958) found 14 ovarian eggs in a
female from Thailand; St. Girons and Pfeffer (1971) reported 10 eggs in a
female from Cambodia; Karsten et al. (1986) examined Hong Kong specimens and
report a litter of five young; Cox (1991) stated females average nine per
litter.
Timing. In Cambodia, St. Girons (1972) described young being born in
the spring; in Laos, Deuve (1970) found neonates throughout the rainy season
and stated the young are born April through August; Saint Girons and Pfeffer
(1972) suggest the young are born in spring in Cambodia. And, St. Girons (1972)
suggested that in Cambodia males start spermatogenesis in August, sexual
activity occurs in November, and females start vitellogenesis in November, with
parturition in the spring.
Batchelor (1958) discussing plumbea wrote, "I once had a female taken from an
estate well which produced nearly thirty youngsters during the following twelve
hours, each a little under three inches in length, greenish in colour...The
adult was 10" in length...was dark purplish brown in colour with a series
of black vertebral spots." The large litter size, adult size, and color of
the offspring make the identification of the snake this statement questionable.
Predators. Mao (1970) found the krait, Bungarus multicinctus, and the common cobra, Naja naja prey upon plumbea. Voris and Karns (1996) suggested that
the mud-root tangle is a relatively predator-free microhabitat. They found it
very difficult to extract the snakes from this refuge and it seems likely that
the snakes are relatively safe from wading birds and large predatory fish.
However, plumbea is probably not safe
from snake predators, in this environment. The population studied by Voris and Karns
(Sabah, East Malaysia) was relatively sedentary and spent the day in the
mud-root tangle, but became more active at night. It also seems likely that plumbea is subject to predation from a
variety of large fish with which it shares its aquatic habitat, particularly
snakeheads (family Ophicephalidae).
Campden-Main (1970) noted that defense behavior in this species differs
with its habitat when it is encountered. He wrote, "The species will not
hesitate to bite if disturbed out of water, but in the water they are shy and
always attempt to escape." This may account for the conflicting
descriptions of its behavior. Batchelor (1963) wrote, it "...merely buried
its head in the soil or under a leaf when disturbed, hoping presumably, that
the action rendered it invisible." Kuntz (1963) wrote about the behavior
of Taiwan specimens. "This snake will strike without provocation and in
contrast to most species is capable of jumping or striking distances
considerably greater than the body length. When excited or attempting to escape
from an intruder, it moves rapidly by a series of erratic lateral jumps. At
times the snake will land on its back or side, flip its body quickly and take
off at 90 degrees from the original path of movement." And, Pope (1935)
described its behavior in China,
The markedly fierce behavior of plumbea
when on the defensive has been recorded by Flower (1899, l.c.) and Schmidt
(1927, l.c.) While on guard, the body forms a single loop and the neck is bent
sharply like a crook. The strike is little more than a frantic jab. I have seen
a specimen progress on a smooth floor by throwing its body forward so the tail
sometimes even fell in front of the head. This is most unusual behavior for a
snake.
Venom. Karsen et al. (1986)
wrote, “Although listed as venomous, it is not considered dangerous to man as
its venom has low toxicity. Its bite may cause slight swelling at most."
D. Karns (personal communication) found that envenomation results in a
immediate burning sensation followed by local swelling, but no systemic
effects; and compared the effects to a bee sting.
Folklore. On Thailand’s Khorat Plateau local people told us that they
use plumbea to rid buildings of ant
infestations. The snakes are cooked and then placed around the inside of a
building. The ants then eat the snakes and die, or turned into a winged form
and disappear.