Glossy Marsh Snake ( Gerarda prevostiana Eydoux & Gervais, 1837 )

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Name
Scientific Name: 
Gerarda prevostiana (Eydoux & Gervais, 1837)
Regional Names: 
English: 
Gerard's Water Snake, Cat-eyed Water Snake
Marathi: 
Zilan
Photographs: 
Distribution: 
Found in all coasts of India including Andaman Islands. Also found in similar habitat of Bangladesh, Cambodia, Indonesia, Malaysia, Myanmar, Singapore, Sri Lanka, Thailand? and Philippines.
Venom Type: 
Neurotoxic
Family: 
Homalopsidae
Characteristics for identification: 

It can be identified by checking shorter length, extremely glossy body of gray-brown color and shorter tail. 

Description: 

Average length- 45cm.
Maximum length- 52cm.

Dorsal -
Body cylindrical to slightly depressed, moderately thick and not much robust as compared to majority of Homalopsidae Family members. Covered with pitted smooth scales which lacks striations. First three dorsal rows yellow-white while rest of dorsal surface glossy gray or reddish-brown

Ventral -
Belly white with a dark mid-stripe in broken or unbroken form or entirely gray with white patches on outer edges.

Head -
Head moderate, slightly depressed and slightly broader than neck, snout rounded. Eyes with vertically elliptical pupil. Nostrils and eyes at the upper level of head which are dorso-lateral (more lateral). Top of the head and upper lip similar to dorsal and belly color respectively. Underside scale also similar to belly but often marked with gray edge.

Tail -
Rather short and thick tail ends with pointed tip. Scales of tail edged with dark color and gives appearance of faint reticulations. Subcaudal scales paired. Color and patterns similar to rest of belly.

Scalation
Head: 
Nasals separated by single internasal; supralabial 7 or rarely 8, 4th in contact with eyes; loreal 1, preocular 1, postocular 2, temporal 1+2 or 2+2.
Dorsal: 
Smooth scales in 17: 17: 13/15 rows.
Ventral: 
144-157; anal divided.
Sub Caudal: 
29-36, paired.
Habitat: 
It is restricted to coastline and rivers ending to sea water. Prefers mangrove waters but occasionally founds in nearby water bodies away from sea. Use mud lobster mounds and other mangrove crustacean burrows as hiding place. Often seen lying on shallow water pool with submerged or exposed body.
Natural History: 
Glossy Marsh Snake is a nocturnal and aquatic species found to be more active during spring tide survey nights. Behavior calm and rarely bites. Moderate swelling on bite site is observed which retains for few hours. Viviperous. Female directly gives birth to 4-6 young individuals during early monsoon.
Diet: 
Feeds on soft bodied crabs, shrimps, mudskippers. This snake is one the few exception in snake world which preys upon some animals (crabs, shrimps etc.) by tearing their body to take the most nutritive part only.
Threats: 
Direct threats like killing and road kills are not much affecting this species but its killed individuals can be seen around fishing sites. Loss of mangrove forests and lands is major cause. Due to conversion of mangrove lands into agricultural fields and salt farms this species is facing threat of permanent vanishing from a particular area.
Authors & Contributors: 
Vivek Sharma
anujshinde