Fig 1
Fig 2
Fig 3
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Family : HOMALOPSIDAE
Species : Gerarda prevostiana
Maximum Size : 58 cm total length
(Source: Murphy, 2007)
Gerarda prevostiana
(Gerard's Water Snake) inhabits coastal habitats, being particularly notable
in mangrove ecosystems. This secretive snake has adapted to unique
microhabitats, including the burrows inside the excavation mounds created by
mud lobsters (Thalassinia spp.) in back-mangrove areas.
It appears particularly active during nocturnal high tides, especially
spring tides, when the flooding of its burrows tends to force the snakes
into the open.
It specialises in feeding on recently moulted crabs; it is able to grasp
these soft, vulnerable crustaceans within its coils and then tear off pieces
of flesh for consumption (Jayne et al, 2002).
Its dorsal surface is
generally brown in colour, but also greyish to blackish. The lower scale rows and
ventral scales are white or pale yellow, as are the labial scales (those
lining the lips) and chin. The head is
barely distinct from the body, and the small eyes are located towards the
top of the head.
Murphy (2007) compiled a
distribution map which included the following locales for Gerarda prevostiana;
west coast of India, west coast of Sri Lanka, parts of coastal Bangladesh
and Myanmar, west coast of Peninsular Malaysia, Singapore (e.g. Pasir Ris
mangrove), eastern Thailand (Chonburi), and western parts of the Philippine
Islands (Luzon, Palawan). There are doubtless many other mangrove sites
where this species occurs.
Gerarda prevostiana is closely-related to the Crab-eating
Water Snake (Fordonia leucobalia).
Figs 1 and 2 : This example from mangrove habitat in Singapore measured 25
cm total length. Thanks to Sohan Shetty
Fig 3 : Mangrove habitat along the west coast of Peninsular Malaysia during
a spring tide. Such events can force Gerarda prevostiana to
vacate its burrows within mud lobster mounds.
References :
Jayne, B.C, H.K. Voris, and P.K.L. Ng. (2002). Snake circumvents constraints
on prey size. Nature 418 (6894): 143.
Murphy, J. C. (2007). Homalopsid Snakes. Evolution in the Mud (Kreiger,
Melbourne, FL). 250 pp.
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