North-western mangrove sea snake (Ephalophis greyae)

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North-western mangrove sea snake
IUCN Red List species status – Least Concern LEAST
CONCERN

Top facts

  • The north-western mangrove sea snake is a relatively small species of sea snake with a small head and a downcurved, paddle-like tail.
  • Although it is a venomous species, the north-western mangrove sea snake does not produce venom as toxic as that of some other sea snake species.
  • The incomplete blackish bands covering the north-western mangrove sea snake’s back often fuse together to form a zig-zag pattern.
  • Known to be a fish eater, the north-western mangrove sea snake may specialise in feeding on gobies.
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North-western mangrove sea snake fact file

North-western mangrove sea snake description

KingdomAnimalia
PhylumChordata
ClassReptilia
OrderSquamata
FamilyElapidae
GenusEphalophis (1)

A venomous species (4) (5), the north-western mangrove sea snake (Ephalophis greyae) is a relatively small, slender sea snake (3) (6) (7) with a small head and a downcurved tail (7). This species is not commonly encountered (1), and is the only species within its genus (3).

The upper surface of the north-western mangrove sea snake is pale cream, grey or pale olive-brown (3) (6) (7) (8) and is marked with a series of dark grey or black blotches which extend to the flanks (3) (7) (8). These blotches, sometimes described as being incomplete bands which do not meet on the underparts, are widest on the upper surface of the snake (7), and often fuse to form an irregular, interrupted zig-zag pattern down the back (3) (6) (7) (8). Black skin is visible between the scales on the body of this species (8). Juvenile north-western mangrove sea snakes are mostly light grey or almost white in colour, making the dark patterns on the back far more conspicuous than in the adults (7).

A characteristic feature of sea snakes is the vertically flattened, paddle-like tail (9), which in the north-western mangrove sea snake is very shallow (3), marked with six dark grey rings, and has a white tip (8). The body scales of this species overlap each other and are smooth along the front and sides of the snake (6) (8), but on the back and towards the hind part of the body the scales have distinctive, blunt keels (3) (6) (7) (8) and often sport darker edging (7).

Also known as
Grey's mangrove seasnake, mangrove seasnake.
Synonyms
Ephalophis greyi.
Size
Length: up to 50 cm (2) (3)
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North-western mangrove sea snake biology

Drifting with the rising tide (6), the north-western mangrove sea snake can be seen foraging among goby burrows and crab holes (1) (6), and is known to search for its prey out of the water on salt flats during low tide (1). This fish-eating species feeds mostly on gobies (1) (6) (10) and their eggs (1), and like other snakes it swallows its prey whole (10). It has been suggested that the north-western mangrove sea snake may have an extremely specialist diet, and may not eat any fish species other than gobies (11). Although a venomous species (4) (5), the north-western mangrove sea snake does not produce venom as toxic as that of many other sea snakes (5).

Despite being an air-breathing animal, the north-western mangrove sea snake is capable of remaining underwater for up to two hours at a time, before surfacing to breathe again. Its single, elongated lung, which extends for almost the entire length of its body, is highly efficient for gas exchange, and sea snakes are also able to absorb oxygen through their skin when underwater. As in other sea snake species, the north-western mangrove sea snake has specialised valves which block off the nostrils while underwater (6).

Living in the marine environment poses several other challenges, and like other sea snake species, the north-western mangrove sea snake has a specialised gland under its tongue which enables it to excrete excess salt from its body. A sea snake sheds its skin approximately once every two to six weeks, by rubbing its lips against something hard such as coral until the loosened skin is anchored there. The sea snake then crawls forwards, leaving the skin turned inside out behind it. By shedding its skin so frequently, a sea snake can get rid of the many marine species, such as algae and barnacles, which become attached to it (6).

Like most species of sea snake, the north-western mangrove sea snake is viviparous, meaning that it gives birth to live young rather than laying eggs. Mating in sea snakes is a lengthy affair, and the males are unable to disengage from the female until copulation is complete. There is no information available on the breeding season of the north-western mangrove sea snake or the number of young produced by this species (6).

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North-western mangrove sea snake range

The north-western mangrove sea snake is endemic to the coast of north-western Western Australia (1) (3) (6) (7), only occurring in a fairly remote area (1). Its range is restricted to parts of the western shelf (2), where it is found from the Kimberley Region to Shark Bay (1).

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North-western mangrove sea snake habitat

The north-western mangrove sea snake inhabits shallow coastal flats (1) (6), where it can be found in estuarine mudflats (1) (2) (3) and, as its name suggests, mangroves (1) (2). This species tends to show a preference for areas with relatively compact or sandy mud, where crab and mud-skipper holes are present (6).

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North-western mangrove sea snake status

The north-western mangrove sea snake is classified as Least Concern (LC) on the IUCN Red List (1).

IUCN Red List species status – Least Concern

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North-western mangrove sea snake threats

Little information is available on the possible threats to the north-western mangrove sea snake (6). However, it is believed that it may potentially be affected by coastal development in certain parts of its range, given that it is a mangrove-associated species. Future industrial activity within the north-western mangrove sea snake’s habitat, including salt extraction, mining and infrastructure development for shipping, has also been identified as a potential threat (1).

Prawn trawling is known to pose a major threat to sea snakes, as the reptiles get caught as bycatch in the trawl nets and often drown or become crushed by the weight of the catch (6).

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North-western mangrove sea snake conservation

Although there are currently no conservation measures in place specifically for the north-western mangrove sea snake (1), this species, along with all other sea snakes in Australia, is nationally protected through its listing under the Environment Protection and Biodiversity Conservation Act 1999 (1) (6).

Marine Bioregional Plans have been developed for four of Australia’s marine regions to improve understanding of Australia’s oceans, identify the conservation values of each marine region, and set out broad biodiversity priorities and objectives. As part of these plans, the north-western mangrove sea snake has been identified as being of conservation value in the Northwest Marine Region (6).

It is believed that industrial activity, including salt extraction and mining, is likely to occur in the north-western mangrove sea snake’s habitat in the future, and it has been recommended that this should be carefully monitored (1).

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Find out more

Find out more about sea snakes:

Learn more about marine conservation in Australia:

Find out more about conservation in Australia:

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This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
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Glossary

Algae
Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
Bycatch
In the fishing industry, the part of the catch made up of non-target species.
Endemic
A species or taxonomic group that is only found in one particular country or geographic area.
Genus
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
Gland
An organ that makes and secretes substances used by the body.
Keel
A projecting ridge along a flat or curved surface, particularly down the middle.
Viviparous
Giving birth to live offspring that develop inside the mother’s body.
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References

  1. IUCN Red List (April, 2013)
    http://www.iucnredlist.org/
  2. Heatwole, H. (1999) Sea Snakes. University of New South Wales Press, Sydney, Australia.
  3. Gopalakrishnakone, P. (1994) Sea Snake Toxinology. National University of Singapore Press, Singapore.
  4. The Reptile Database (April, 2013)
    http://reptile-database.reptarium.cz/search.php
  5. Descotes, J. (1996) Human Toxicology. Elsevier, Philadelphia.
  6. Department of Sustainability, Environment, Water, Population and Communities (2012) Ephalophis greyi. In: Species Profile and Threats Database. Department of Sustainability, Environment, Water, Population and Communities, Canberra. Available at:
    http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=1127
  7. Smith, L.A. (1974) The sea snakes of Western Australia (Serpentes: Elapidae, Hydrophiinae) with a description of a new subspecies. Records of the Western Australian Museum, 3(2): 93-110.
  8. McDowell, S.B. (1974) Additional notes on the rare and primitive sea-snake, Ephalophis greyi. Journal of Herpetology, 8(2): 123-128.
  9. 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 Organization of the United Nations, Rome. Available at:
    ftp://ftp.fao.org/docrep/fao/009/y0870e/y0870e65.pdf
  10. Tomascik, T. and Mah, A.J. (1997) The Ecology of the Indonesian Seas. Tuttle Publishing, Vermont.
  11. Voris, H.K. and Voris, H.H. (1983) Feeding strategies in marine snakes: An analysis of evolutionary, morphological, behavioral and ecological relationships. American Zoologist, 23: 411-425.
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North-western mangrove sea snake  
North-western mangrove sea snake

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