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Characteristics: The only known pelagic specie of sea snake and the sole specie of the genus Pelamis. This snake is easily identified by its characteristic bright yellow underside which could well be an adaptation to protect it from predators for it provides adequate camouflage against the water when seen from below. This snake has a dark dorsal colouration and some may have spots on their tail. Such a colouration would come in handy while ambushing fish. It is a relatively small snake with a slender body and prominent caudal fin, which is in fact its modified tail. Nearly incapable of terrestrial locomotion.

Adult Specimen Swimming	Stranded Specimen	Specimen in Water

Behaviour: It is a very powerful swimmer but can also float. It prefer the continental shelf but and is occasionally recorded far out in the open ocean which would explain its wide distribution. This snake is capable of cutaneous respiration (directly absorbing oxygen from water) and can remain submerged for up to 3 hours. It is highly diurnal and often spends the night on the seabed. Highly docile in nature and most likely to ignore fishermen who may handle it with impunity.

Food: This specie feeds exclusively on fish. It ambushes its prey which it kills relatively quickly using its highly potent venom.

Breeding: This specie is viviparous. The brood size is small and within the range of 2 to 10. It does not seem to have a definite breeding season and its reproductive habits vary along its wide distribution. Apparently those that inhabit Sri Lankan waters tend to give birth between January and March when the seas are calm during the inter monsoon phase. The gestation period of these snakes is uncertain and most possibly in the area of 5 to 6 months.

Growth: Upon birth neonates measure between 220-260mm. This snake grows to a maximum length of around 100cm and reaches sexual maturity when over 60cm long.

Venom: The lethal venom possessed by this snake is capable of killing a human being within 2 hours. The venom is neurotoxic yet only a handful of fatalities have been attributed to this snake. Unfortunately in Sri Lanka specimens that get accidentally caught in fishing nets are occasionally sold as "exotic eels." There have been cases where people have died after consuming flesh and foetuses of this snake.

Identification: Can be identified at a glance due to its unique and distinct yellow ventral colouration. It can also be distinguished from the fact that it has between 40 to 54 rows of costals two head lengths behind its head. The width of its costals is also greater than the length.

Lepidosis:

• Frontal: In contact with six other shields. Its width is half its length and appears to be rather elongated.
• Supraoculars: Around three-quarters of the area of the Frontal and nearly as broad but markedly shorter.
• Prefrontals: In contact with the second pair of Supralabials and the Preocular shields. Occasionally in anomalous specimens does not meet the second Supralabial and contacts only the Nasal and Preocular shields.
• Parietals: Very prominent and nearly twice the length of the Frontal. The contact length is over 4/5 of the total length.
• Nasal: Same width as the Prefrontals and directly in contact with them. Nostrils situated towards the outer extreme.
• Rostral: In contact with the Nasals and first pair of Supralabials. Broad and spans half the length of the Nasal pair.

• Preocular: Elongated and touches the second, third and fourth pairs of Supralabials.
• Postocular: Differentiates into two and sometimes three smaller shields which follow a concentric radial pattern around the eye. Lowermost shield often in contact with the fifth and sixth pairs of Supralabials.
• Temporals: Small and less prominent. Touches the Parietals and two of the Postoculars.
• Supralabials: Up to eight pairs with the second pair being the largest. Often the fourth and fifth pairs may be divided. Rarely the ones that follow.
• Infralabials: Five pairs which decrease in size with the first pair nearly three times the size of the second pair.
• Mental: Takes the stereotype form.
• Loreal: Absent but small ones may be present in anomalous specimens.
• Sublinguals: Either obscure or absent.

• Costals: Considerably wider than their length unlike other species. Takes a depressed hexagonal form with a double indentation in the centre. Highly smoothed and uniform with no difference in size in the Vertebral and Ultimate rows.
• Ventrals: Small and vestigal. An average individual may possess c.280-c340 rows.
• Anal: Divided into four smaller shields.

Dentition:

• Maxillary: 8 to 10
• Palatine: 6 to 7
• Pterygoid: 23 to 27
• Mandibular: 16 to 18

Distribution: Indian Ocean, Australia, New Zealand, and northern Pacific Ocean from Japan to the western coast of North America. It is an ubiquitous and abundant specie with a low risk designation.

A fairly common specie in Sri Lankan waters, often found around the continental shelf. May venture close to the beaches where it often gets caught in fishing nets.

References:

WALL, Frank: Snakes of Ceylon (1921)

Additional Reference from a page by Jennifer Liptow, Biology 108 student (1995).
The Regents of the University of Michigan

Acknowledgements:

Photographs from The Regents University of Michigan and Smithsonian? Websites (Photographers Unknown)