Banded sea krait (Laticauda colubrina)
|Also known as:||Columbrine sea krait, large-scaled sea krait, yellow-lipped sea krait|
|Synonyms:||Coluber platycaudatus, Hydrophis colubrine, Hydrus colubrinus, Laticauda frontalis, Laticauda scutata, Platurus colubrinus, Platurus fasciatus, Platurus frontalis, Platurus laticaudatus|
|Size||Male total length: c. 87.5 cm (2)|
Female total length: c. 142 cm (2)
Male tail length: c. 13 cm (2)
Female tail length: c. 14.5 cm (2)
The banded sea krait is classified as Least Concern (LC) on the IUCN Red List (1).
The banded sea krait (Laticauda colubrina) is an amphibious species of snake that spends most of its life at sea but comes to land to reproduce. In adaptation to this curious semi-aquatic lifestyle, the banded sea krait has evolved unusual morphology. It has retained the ventral scales and cylindrical body shape that is typical of terrestrial snakes, as this helps with climbing on land and in low trees, but its tail is paddle-shaped, which allows rapid movement in water. It also has large lungs so that it can spend long periods under water, as well as valved nostrils that keep out saltwater while diving, and glands under the tongue that expel excess salt (3).
The banded sea krait displays marked sexual dimorphism, the female being heavier and around a third longer than the male (4). The head and tail look rather similar, which perhaps serves to confuse predators by drawing their attack to the tail, which is less likely to result in fatal injuries. The small head is slightly distinct from the body, which is bluish-grey with smooth, regularly-spaced scales (5). Equal-sized black bands circle the entire length of the body and contrast sharply with the yellow or cream underparts (3) (5). The snout, upper lips and a bar above the eyes are yellow, but the remainder of the head is black (3).
The banded sea krait is one of the most widespread species in the genus Laticauda. It occurs along coasts in the eastern Indian Ocean, east through Malaysia, Indonesia and Papua New Guinea to islands of the south-western Pacific, and north to Vietnam, southern China, Taiwan, and the Ryuku Islands, Japan. It may occasionally stray into waters off Australia and New Zealand, as well as waters near the western coast of Central America (1).
The banded sea krait is usually found in shallow tropical waters surrounding coral islands, coral reefs and mangroves, to depths of around ten metres (3). On land, it shelters in vegetation, under beach rocks, in crevices and in caves (1).
As an oviparous snake, the banded sea krait must come ashore on small remote islands to lay its eggs. Females can lay at any time of year, with clutch sizes ranging from 4 to 20 eggs (3). Only two nests have ever been reported, meaning its reproductive biology is poorly understood (1). However, it is thought that few juvenile snakes reach maturity due to high levels of predation. Male banded sea kraits reach maturity at around 18 months, but females may take 24 months before being ready to breed (3).
Due to the pronounced sexual dimorphism in this species, male and female banded sea kraits exhibit different foraging strategies (1) (3). Both the male and female prefer to feed on eels, but the males tend to take smaller eels near the sea floor, while females eat larger eels which they capture in crevices in coral reefs (3). The banded sea krait has also been seen actively hunting on the shore, even at low tide, when it probes amongst coral rubble for scraps of food (5). It also comes ashore to rest, digest its food and shed its skin (1) (5).
The banded sea krait is highly venomous, but its relatively docile nature means that it rarely bites humans (3) (5).
Although widespread and abundant at many locations, the banded sea krait is threatened by climate change, and by disturbances to both its marine and terrestrial habitats (1).
As an amphibious species, the banded sea krait uses shore habitats for laying eggs, digesting prey and moulting. Egg laying only occurs at certain tides, when shore habitats are accessible. Therefore, sea level rise associated with climate change could threaten this species, by rendering many sites unusable for egg laying and other activities (1).
Climate change may also threaten this species through the loss of its coral reef habitat. Elevated sea temperatures will increase the risk of coral bleaching, in which the stressed corals expel their symbiotic algae known as ‘zooxanthellae’, often resulting in the death of the coral. Climate change may also lead to more frequent, severe storms, which can damage reefs, while rising carbon dioxide levels may make the ocean increasingly acidic, weakening the coral’s skeleton. Such stresses can also make corals more susceptible to disease, parasites and predators (6) (7) (8).
Coastal developments and other human disturbances also threaten the banded sea krait and its habitats. This species is attracted to light and may be affected by lighting from hotels and beach shacks. In addition, the banded sea krait is hunted for food in parts of its range, including in the Philippines, where it is smoked and exported to Japanese markets (1).
The banded sea krait has not been the target of any known specific conservation measures, but its habitat is afforded some protection in a number of Marine Protected Areas. It is also found in two sea snake sanctuaries at Gato Island and Pulo Laum in the Philippines. Any future conservation measures for this species should take into account both its terrestrial and marine habitat requirements (1).
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- Algae: simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
- Amphibious: capable of living both on land and in water.
- 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.
- Morphology: the visible or measurable characteristics of an organism.
- Oviparous: an animal that reproduces by laying eggs, which hatch outside the mother’s body.
- Sexual dimorphism: when males and females of the same species differ in appearance.
- Symbiotic: describes a relationship in which two organisms form a close association. The term is now usually used only for associations that benefit both organisms (a mutualism).
IUCN (March, 2011)
The Reptile Database - Laticauda colubrina (March, 2011)
James Cook University - Laticauda colubrina (March, 2011)
- Heatwole, H. (1999) Sea Snakes: Australian Natural History Series. UNSW Press, Sydney.
Wild Singapore - Yellow-lipped sea snake (March, 2011)
- Wilkinson, C. (2004) Status of Coral Reefs of the World: 2004. Volume 3. Australian Institute of Marine Science, Townsville, Australia.
- Carpenter, K.E. et al. (2008) One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science, 321: 560-563.
- Miththapala, S. (2008) Coral Reefs. Coastal Ecosystems Series (Volume 1). Ecosystems and Livelihoods Group Asia, IUCN, Colombo, Sri Lanka.