Beaked sea snake (Enhydrina schistosa)

Also known as: common sea snake, hook-nosed sea snake, Valakadyn sea snake
Synonyms: Disteira russelii, Disteira schistosa, Enhydrina valakadien, Enhydrina valakadyen, Enhydrina valakadyn, Enhydrina velakadien, Enhydrina vikadien, Hydrophis bengalensis, Hydrophis fasciatus, Hydrophis schistosa, Hydrophis schistosus, Hydrophis subfasciata, Hydrus valakadyn, Polyodontes annulatus, Thalassophis werneri
  
French: Enhydrine Ardoisee
KingdomAnimalia
PhylumChordata
ClassReptilia
OrderSquamata
FamilyHydrophiidae
GenusEnhydrina (1)
SizeLength: up to 140 cm (2) (3)

The beaked sea snake is classified as Least Concern (LC) on the IUCN Red List (1).

The beaked sea snake (Enhydrina schistosa) gains its common name from the distinctive downturned, beak-like projection on the snout, at the front of the upper jaw (3) (4). Like other sea snakes, this species is highly adapted to life at sea, possessing a flattened, paddle-like tail for swimming, as well as valved nostrils, which can be closed when the snake is underwater. Sea snakes also lack the expanded belly scales that most other snakes use for moving on land (2) (3) (5).

The body of the beaked sea snake is quite stout and vertically flattened, with a relatively small head (3). The adult is dull olive-green or greenish-grey above and whitish below, with dark crossbands that tend to fuse together towards the tail. The crossbands are widest on the upperside, tapering to points on the flanks, and usually disappear in older adults, which are a more uniform bluish-grey colour (1) (3).

The beaked sea snake is widespread in the Arabian Gulf and Gulf of Oman, the northern and eastern Indian Ocean, Southeast Asia, and the western Pacific Ocean, north to Vietnam and south as far as Australia and Papua New Guinea (1) (2) (3) (4) (6).

The beaked sea snake inhabits shallow waters with muddy or sandy bottoms, particularly over mud flats in estuaries and at river mouths (2) (3) (4).

Feeding mainly on catfish, the beaked sea snake will also feed on pufferfish and occasionally other fish or squid species (2) (4) (7) (8). Prey is thought to be located by touch and by detecting movement, rather than by vision, allowing the beaked sea snake to hunt in low-visibility waters (4) (8). Prey is swallowed whole, head first (7), after first being overcome by the snake’s powerful venom (3).

Sea snakes are among the most venomous of the world’s snakes (3), and the beaked sea snake is one of the most dangerous (1) (2). Most sea snakes rarely bite, and often do not inject much venom when they do, but this species is more aggressive than most (2). Just 1.5 milligrams of the beaked sea snake’s venom is enough to kill a human, with a full dose estimated to be enough to kill 22 people. Most fatalities from beaked sea snake bites occur where it frequently comes into contact with humans, such as in shallow estuaries or when it is removed from fishing nets (1) (4).

The beaked sea snake mates in September and October, and breeding is likely to be annual (8). Female sea snakes give birth to relatively large, live young, and this species produces the largest litter of any sea snake, giving birth to an average of 18 young, but sometimes up to 30 or more (3) (4). Mortality of young beaked sea snakes is likely to be high (4) (9), but those that survive grow rapidly. Maturity is reached at around 18 months, the female usually giving birth to the first clutch of young at around 24 months (9).

Little is known about the conservation status of this and other sea snakes (3). Many are exploited for the skins, organs and meat (2), but the extent of this threat to the beaked sea snake is unknown, as is the extent to which it may occur as bycatch in other fisheries (4).

Other, more general threats to marine ecosystems, such as overfishing, pollution and climate change, may also potentially impact this snake. Easily injured if handled even gently, the beaked sea snake may not be an easy species to maintain in captivity (4).

In the waters around Queensland, Australia, a special licence is now needed to collect sea snakes, but most sea snake fisheries in the Indian and Pacific Oceans are not regulated and their impacts are virtually unknown (2). Despite some species being taken in large numbers, no sea snakes are listed under the Convention on International Trade in Endangered Species (CITES) (10).

Much more needs to be known about the biology and abundance of the beaked sea snake, and the threats its faces, before its conservation status can be properly assessed and, if needed, any appropriate conservation action taken.

Find out more about the beaked sea snake and other sea snake species:

For more information on the conservation of snakes and other reptiles:

Authenticated (25/10/11) by Olivier S.G. Pauwels, Research Associate at the Royal Belgian Institute for Natural Sciences, Brussels, Belgium.
http://www.pauwelsolivier.com/

  1. IUCN Red List (April, 2011)
    http://www.iucnredlist.org/
  2. Carpenter, K.E. and Niem, V.H. (2001) The Living Marine Resources of the Western Central Pacific. Volume 6: Bony Fishes Part 4 (Labridae to Latimeriidae), Estuarine Crocodiles, Sea Turtles, Sea Snakes and Marine Mammals. Food and Agriculture Organisation of the United Nations, Rome. Available at:
    ftp://ftp.fao.org/docrep/fao/009/y0870e/y0870e66.pdf
  3. Hellyer, P. and Aspinall, S. (2005) The Emirates: A Natural History. Trident Press Limited, London.
  4. O’Shea, M. (2008) Venomous Snakes of the World. New Holland Publishers, London.
  5. Halliday, T. and Adler, K. (2002) The New Encyclopedia of Reptiles and Amphibians. Oxford University Press, Oxford.
  6. The Reptile Database (March, 2012)
    http://reptile-database.reptarium.cz/species?genus=Enhydrina&species=schistosa&search_param=%28%28taxon%3D%27Elapidae%27%29%29
  7. Voris, H.K. and Moffett, M.W. (1981) Size and proportion relationship between the beaked sea snake and its prey. Biotropica, 13: 15-19.
  8. Voris, H.K., Voris, H.H. and Liat, L.B. (1978) The food and feeding behavior of a marine snake, Enhydrina schistosa (Hydrophiidae). Copeia, 1: 134-146.
  9. Voris, H.K. and Jayne, B.C. (1979) Growth, reproduction and population structure of a marine snake, Enhydrina schistosa (Hydrophiidae). Copeia, 2: 307-318.
  10. CITES (July, 2009)
    http://www.cites.org/