Black-banded sea krait (Laticauda semifasciata)

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Black-banded sea krait fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Black-banded sea krait description

The highly venomous black-banded sea krait (Laticauda semifasciata) can be identified by the distinctive black or dark brown bands running down the length of its body ^{(4) (5) (6)}. The blue, grey or greenish ground colour that intersperses the banding on the top of the body merges with yellow colouring on the lower half of the body, with the very underside of the snake being grey-white or pale blue ^{(5) (6)}. In older black-banded sea kraits, the bands fade slightly and become lighter in colour. This species has a dark brown head with a curved white or yellowish mark on the top ⁽⁶⁾.

Like land snakes, the black-banded sea krait has scales, a forked tongue, lidless eyes and breathes air ⁽⁷⁾. However, it shows a number of differences to land snakes due to the large proportion of time the snake spends underwater. For example, the black-banded sea krait has a short, flattened tail which allows the snake to propel itself quickly when swimming. Furthermore, these snakes have glands under the tongue to combat excess salt in seawater, and they also have an increased lung size ^{(8) (9)}.

The black-banded sea krait is the bulkiest snake in the genus Laticauda ⁽⁵⁾. Size differences can be found between males and females, with females on average being longer and weighing more. Further differences can be found in the number of scales on the underside of the tail, with males having more scales than females ⁽³⁾.

Also known as

Chinese sea krait, Chinese sea snake.

Synonyms

Platurus semifasciatus, Pseudolaticauda semifasciata.

Size

Male snout-vent length: c. 80.5 cm ⁽²⁾

Female snout-vent length: c. 119.5 cm ⁽²⁾

Male tail length: c. 11.5 cm ⁽²⁾

Female tail length: c. 11.5 cm ⁽²⁾

Average male weight: 496 g ⁽³⁾

Average female weight: 895 g ⁽³⁾

Black-banded sea krait biology

The black-banded sea krait spends the majority of its time in the water, but ventures onto land to mate, digest food, rest and lay eggs ^{(10) (11)}. This species is active during the day ⁽¹²⁾. Its breeding activity is highest between August and November. Females lay three to seven eggs, depending on the length of their body, in large coral caves. The eggs are half submerged in water and hatch after around four to five months ⁽³⁾.

One of the most remarkable details about the black-banded sea krait is that despite its highly toxic venom ^{(4) (5) (8) (9) (13)} it has a very mild nature ^{(12) (13)}. Even when being held loosely by researchers, most of the snakes preferred to wriggle to try and escape rather than bite, and even when held tightly the snakes only responded with slow and delayed attacks ⁽¹³⁾. Amazingly, because of this fishermen will handle the black-banded sea krait freely, without fear ⁽⁸⁾.

Like many other snakes, the black-banded sea krait eats large meals infrequently ⁽¹⁴⁾. It preys on a variety of fish that live among the coral ⁽¹⁰⁾, with differences in fish preference between juveniles and adults ⁽¹⁴⁾. Male and female black-banded sea kraits also tend to prey upon different species of fish ⁽¹⁴⁾. To catch its prey the black-banded sea krait swims near the bottom of the reef, flicking its tongue to smell prey and sticking its head into crevices where fish could be hiding. Once the prey is found it is bitten, injecting the snake’s venom, and is usually swallowed quickly, head first ⁽⁷⁾.

Predators of the black-banded sea krait include carnivorous mammals such as the masked palm civet (Paguma larvata), which has been known to catch the snakes when they venture onto land ⁽¹⁰⁾. Like other sea snakes, the black-banded sea krait may also face predation from animals such as sharks and seabirds ^{(9) (15)}. In addition, the snakes can become infested by ticks and small marine organisms that try to grow on them, which the snakes can counter by shedding their skin ⁽⁷⁾.

Black-banded sea krait range

The black-banded sea krait is found in the western Pacific Ocean, along coasts in the Philippines, Taiwan, China and Japan ^{(1) (6) (7)}. It has also been reported from Palu Api in Indonesia ^{(1) (6)}.

Black-banded sea krait habitat

The black-banded sea krait is amphibious in nature and so lives in both a marine and terrestrial environment ⁽¹⁾, although it may be more aquatic than other Laticauda species ⁽¹⁰⁾. In water it is usually found in shallow tropical reefs with many crevices and holes in which it can hide ⁽¹⁰⁾. On land the snake favours rocks which are exposed to open sea and close to the water’s edge ^{(1) (8)}. The black-banded sea krait is also found in coral caves, especially when females lay their eggs ^{(3) (6)}.

Although the black-banded sea krait lives in a marine environment, it requires access to freshwater to drink. Such sources of freshwater may come, for example, from the outflow of rivers and springs into the sea in coastal areas ⁽¹⁰⁾.

Black-banded sea krait status

The black-banded sea krait is classified as Near Threatened (NT) on the IUCN Red List ⁽¹⁾.

Black-banded sea krait threats

The main threat to the black-banded sea krait is from fishermen who harvest the snake for food or its skin, which is used to make leather. During the 1930s, it was reported that as many as 20,000 to 30,000 sea snakes, predominantly the black-banded sea krait, were being killed for their skins each year on Gato Island in the Philippines ⁽⁴⁾. Furthermore, in 1974 it was found that a staggering 450,000 sea snakes were harvested in the Philippines ⁽¹⁾.

Due to these continued harvests it is thought that the populations of the black-banded sea krait in the Philippines have declined by over 90 percent since 1974. Although extensive collections of the black-banded sea krait in the Philippines have stopped, its population numbers show no signs of increasing. This may be due in part to harvesting still happening in Japan and the Ryukyu Islands ⁽¹⁾.

Other threats to the black-banded sea krait include rising sea levels caused by climate change, which may cause the intertidal regions that this species inhabits to be covered ^{(1) (16)}. In addition, changes in sea level may cause some of the caves used as egg-laying sites to become unusable. The loss of live coral due to rising sea temperatures caused by climate change may have a two-fold impact on the black-banded sea krait, firstly by destroying its habitat and secondly by causing a decrease in the abundance of its prey ⁽¹⁾.

In light of these threats there are calls for further investigations into the population numbers of the black-banded sea krait, as it is possible that this species should be listed under a more threatened category on the IUCN Red List ⁽¹⁾.

Black-banded sea krait conservation

Although there are no species-specific conservation measures currently in place for the black-banded sea krait, two sanctuaries have been set up in the Philippines for sea snakes in general ⁽¹⁾. Additionally, efforts to conserve coral reefs are underway in the region and should help protect the black-banded sea krait by conserving its habitat ⁽¹⁷⁾.

As the black-banded sea krait depends on both marine and terrestrial environments, it is vital that any conservation measures for this species take both these habitat needs into account ⁽¹⁾.

Find out more

Find out more about the black-banded sea krait:

• The Reptile Database - Laticauda semifasciata:
  http://reptile-database.reptarium.cz/species?genus=Pseudolaticauda&species=semifasciata

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Glossary

Carnivorous

Feeding on flesh.

Gland

An organ that makes and secretes substances used by the body.

Intertidal

Pertaining to the intertidal zone, the region between the high tide mark and low tide mark.

References

1. IUCN Red List (December, 2012)
   http://www.iucnredlist.org/
2. The Reptile Database - Laticauda semifasciata (December, 2012)
   http://reptile-database.reptarium.cz/species?genus=Pseudolaticauda&species=semifasciata
3. Tu, M.C., Fong, S.C. and Lue, K.Y. (1990) Reproductive biology of the sea snake, Laticauda semifasciata, in Taiwan. Journal of Herpetology, 24(2): 119-126.
4. Herre, A.W.C.T. and Rabor, D.S. (1949) Notes on Philippine sea snakes of the genus Laticauda. Copeia, 1949(4): 282-284.
5. Toriba, M. (1994) Sea snakes of Japan. In: Gopalakrishnakone, P. (Ed.) Sea Snake Toxinology. Singapore University Press, Singapore.
6. Tomascik, T., Mah, A.J., Nontji, A. and Moosa, M.K. (1997) The Ecology of the Indonesian Seas. Part Two. Periplus Editions, Hong Kong.
7. Heatwole, H. (1999) Sea Snakes. University of New South Wales Press, Sydney.
8. Herre, A.W.C.T. (1942) Notes on Philippine sea-snakes. Copeia, 1942(1): 7-9.
9. Heatwole, H. (1978) Adaptations of Marine Snakes: unusual physiological strategies have enabled some snakes to live in a saltwater environment. American Scientist, 66(5): 594-604.
10. Liu, Y.L., Chen, Y.H., Lillywhite, H.B. and Tu, M.C. (2012) Habitat selection by sea kraits (Laticauda spp.) at coastal sites of Orchid Island, Taiwan. Integrative and Comparative Biology, 52(2): 274-280.
11. Heatwole, H., Grech, A., Monahan, J.F., King, S. and Marsh, H. (2012) Thermal biology of sea snakes and sea kraits. Integrative and Comparative Biology, 52(2): 257-273.
12. Dunson, W.A. and Minton, S.A. (1978) Diversity, distribution, and ecology of Philippine marine snakes (Reptilia, Serpentes). Journal of Herpetology, 12(3): 281-286.
13. Tu, M.C. and Su, Y. (1991) The aggressiveness of the sea snake Laticauda semifasciata in Taiwan. Bulletin of the Institute of Zoology, Academia Sinica, 30(1): 55-58.
14. Su, Y., Fong, S.C. and Tu, M.C. (2005) Food habits of the sea snake, Laticauda semifasciata. Zoological Studies, 44(3): 403-408.
15. Voris, H.K. and Jeffries, W.B. (1995) Predation on marine snakes: a case for decapods supported by new observations from Thailand. Journal of Tropical Ecology, 11(4): 569-576.
16. Meehl, G.A., Washington, W.M., Collins, W.D., Arblaster, J.M., Hu, A., Buja, L.E., Strand, W.G. and Teng, H. (2005) How much more global warming and sea level rise? Science, 307: 1769-1772.
17. Chou, L.M. (1997) The status of Southeast Asian coral reefs. In: Lessios, H.A. and Macinture, I.G. (Eds.) Proceedings of the Eighth International Coral Reef Symposium. Volume 1. Smithsonian Tropical Research Institute, Panama.