Crab-eating Snake ( Fordonia leucobalia Schlegel, 1837 )

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Name
Scientific Name: 
Fordonia leucobalia (Schlegel, 1837)
Regional Names: 
English: 
White-bellied mangrove snake
Photographs: 
Distribution: 
In India its distribution is restricted to West Bengal (Sundarbands), Odisha (Dharma and surrounding), Nicobar Islands. Also found Australia, Bangladesh, Cambodia, Indonesia, Malaysia, Myanmar, Papua New Guinea, Philippine Islands, Singapore, Thailand and Vietnam.
Family: 
Description: 

New born- 18cm.
Average length- 50cm.
Maximum length- 94cm.

Dorsal -
Body stout, thick, robust and covered with subequal smooth scales. Color and patterns variable according to geographical range. Grayish-brown with or without irregular dark patches. First 2-3 rows of cream color or similar to belly. Other forms are not found in Indian subcontinent. These include 1) red dorsal with white cross bands which are margined by black. 2) yellow or orange dorsal marked with black vertebral spots or bands 3) blackish dorsal marked white crossbars or spots on vertebral line and lateral white spots.

Ventral -
Belly yellowish-white which extends up to 3 dorsal rows.

Head -
Head short, slightly depressed and not broader than neck; snout obtusely rounded. Small eyes with vertically elliptical pupil. Nostrils and eyes at the upper level of head which are dorso-lateral (more lateral). Top of the head either similar to ground dorsal color or darker. Upper lip whitish but in linear manner and usually more on posterior lips.

Tail -
Rather short and thick tail ends with pointed tip. Males have slightly longer and more compressed tail with dorsal hump from 4th to 26th subcaudal while in females tail gradually tapers to a point. Color and patterns of both upper and lower side similar to rest of body. Subcaudal scales usually paired.

Scalation
Head: 
Scales imbricate; internasal 1, seperates nasals which are usually semi-divided; supralabial 5 or 6, 3rd or 2nd & 3rd in contact with eyes; loreal usually absent; preocular 1, postocular 1-2, anterior temporal usually 2; first three infralabials in contact with anterior chin shield; second pair if present remain in contact with each other.
Dorsal: 
Imbricate, lanceolate and smooth scales arranged striated in 25-27: 25-29: 21-23 rows.
Ventral: 
137-159, last 1 or 2 may be divided; anal divided.
Sub Caudal: 
27-43, paired; hemipenis extends to 14th caudal plate.
Habitat: 
Found in mangroves and nearby mud flats; may comes on wet monsoon forests few times. Choose mud lobster mound, crab holes, mud-root tangle etc. for hiding.
Natural History: 
Nocturnal and aquatic. Prone activity seen during whole of night but occasionally seen during day time and can hunt on prey. Locomotion typically like other Homalopsidae in side-winding manner on mud flats. Behavior usually non-offensive but bites on mishandling which causes mild swelling sometimes. Viviparous. Eggs become mature during June-July when breeding takes place. Embryonic development takes place during August to January. Birth takes place during post winter to summer months. Known litter size 2-17.
Diet: 
Feeds actively on crustaceans including crabs and mud lobsters. Its done either by 1) constriction by pressing the prey into mud to break their limbs 2) by chewing them in burrows until they dismembered 3) pinning prey into mud with chin. It is possible that crabs autonomize their legs instead of letting snake to chew or break them.
Threats: 
Population status of this species is directly related to status of mangrove forests of its range. This is one of the frequently seen snake in fishing net. However it is a common snake component of its habitat.
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