Animal Diversity Web

Geographic Range

Laticauda colubrina, also known as banded sea kraits, originated in the region of northern Papua New Guinea. This species of sea krait is the most widely distributed of the Laticauda complex which includes the related species, Laticauda colubrina and Laticauda saintgirosi. The breeding range of banded sea kraits is limited to the Australian and Oriental Oceanic geographic ranges. Because they inhabit coral reefs and live mostly off the coast of small islands, they have a patchy geographic distribution, a characteristic off most sea snake species. Generally, they are widespread through Indo-Australian Archipelago, the Bay of Bengal, Thailand, Malaysia, and Singapore. More specifically, the breeding range extends westward to the the Andaman and Nicobor Islands and northward to Taiwan and the Miyako and Yaeyaema island groups in the southwestern part of the Ryukyu Archipelago in southern Japan. They are present off the coast of Thailand but only on its western coast. Their eastern limit is Palua and they are present on the island groups from the Solomon Islands to Tonga in the southwestern Pacific. Their distribution is heavily reliant on several key factors including the presence of coral reefs, sea currents, suitable terrestrial shelter, and paleography. They are not found in the Atlantic and Caribbean oceanic regions. (Cox, et al., 1998; Heatwole, et al., 2005)

• Biogeographic Regions
• oriental
  • native
• australian
  • native

Habitat

Banded sea kraits are found most frequently in warm, tropical climates in oceanic, coastal waters. Many are found off the shore of small islands and they often hide in small crevices or under rocks. Their primary habitat is shallow coral reef waters where their primary food source (eel) resides. They have many special adaptations for diving including a saccular lung allowing them to dive to depths up to 60 m in search of food. They spend a much of their lives in the ocean but also spend anywhere between twenty-five and fifty percent of their life on rocky islets in order to court, mate, lay eggs, digest food, and shed their skins. They can also be found in mangrove areas. They have the ability to climb trees and have even been recorded at the highest points of the islands in which they reside (36 to 40 m high). They are not characterized as a pelagic species. (Heatwole, et al., 2005; Shine, et al., 2002; Tweedie, 1953)

• Habitat Regions
• tropical
• saltwater or marine

• Aquatic Biomes
• reef
• coastal

• Other Habitat Features
• intertidal or littoral

• Range elevation

  36 to 40 (high) m

  ft

• Range depth

  60 (low) m

  196.85 (low) ft

• Average depth

  <20 m

  ft

Physical Description

Banded sea kraits are also called yellow-lipped sea kraits because of a characteristic yellow upper lip. Their heads are mostly black with a yellow band extending along the lip, underneath each eye. They also have a yellow snout and a yellow band above the eye. Similarly, their tails have a U-shaped yellow marking along the edge that borders a broad black band. They have a smooth, scaled body with a blue or gray base color. Twenty to sixty-five black bands form rings around the body. Their ventral surface is typically yellow or a cream color. There is apparent sexual dimorphism in the species most likely due to differences between male and female feeding patterns. Females feed on a larger species of eel that lives in deeper water while the males feed on smaller eels that inhabit shallow water. Therefore, females, weighing about 1800 g and measuring 150 cm in length on average, are typically larger than males which are only 600 grams on average and 75 to 100 cm in length. One giant sea krait has been reported at 3.6 m.

Also, their amphibious nature contributes to their morphological characteristics. For example, they lay eggs and digest food on land and have terrestrial adaptations similar to other terrestrial snakes such as a cylindrical body shape and ventral scales for crawling and climbing on land. However, they hunt and catch prey in the ocean and have certain aquatic adaptations for life in the water including valvular nostrils, salt glands, and a laterally compressed, paddle-like tail similar to true sea snakes. Because of the geographic distribution of the sea kraits, groups from different islands may vary in some physical characteristics such as head shape and size. (Heatwole, 1999; Rasmussen and Elmberg, 2009; Shine, et al., 2002)

• Other Physical Features
• heterothermic
• venomous

• Sexual Dimorphism
• sexes alike
• female larger

• Average mass

  600 to 1800 g

  oz

• Range length

  75 to 360 cm

  29.53 to 141.73 in

• Average length

  125 cm

  49.21 in

Development

When banded sea kraits hatch from the eggs they resemble small adults. They do not undergo any metamorphosis. They display determinant growth with rapid growth in young sea kraits which gradually ceases shortly after sexual maturity is reached. Males reach sexual maturity at about one and a half years and females are sexually mature at one and a half to two and a half years. However, not much has been studied on the specific topic of development in banded sea kraits. (Heatwole, 1999; Heatwole, et al., 2005)

Reproduction

In banded sea kraits, internal fertilization is accomplished by reproductive organs called "hemipenes". Males have two of these reproductive organs and, although both are fully functional, only one is used in any given mating. They are sheathed and lie at the base of the tail. During mating, one of the hemipenes protrudes from its sheath and turns inside out. In this conformation, its surface is covered with spikes and hooks that help secure in the cloaca of the female while mating. (Heatwole, 1999)

Three main phases of banded sea krait courtship and reproduction have been described. The first phase is called the tactile phase. Males may swim around the shore attempting to find the point of exit of a female that has gone to land. This phase demonstrates the reliance of the sea kraits on pheromonal cues in order to locate and follow the trail of a female. The second phase includes mounting and body alignment. In this stage, a male will drape itself over a female and often twitch spasmodically in an attempt to stimulate the female. Finally, the third phase refers to the actual copulation of the sea kraits. Copulation in sea kraits involves the insertion of the hemipenis of the male into the cloaca of the female.

In a study of mating groups on a small Fijian island, 51% were a male and female pair, and the remainder involved a female and 2 to 9 males. However, males do not appear to exhibit any interaction or competition. Also, in the vast majority of cases, only one male actively courts with a female while the others simply wait and maintain contact with the female. This may reveal two different strategies for male courtship in sea kraits. In one strategy, the male actively tries to stimulate the female until it is ready to copulate. In the other strategy, a male is opportunistic, waiting for the moment in which the female is ready to copulate, then rapidly aligning its cloaca with that of the female. Therefore, in contrast to some other snake species, reproductive success in males seems independent of their body size and strength. On the other hand, the attractiveness of females does have a direct correlation with body size as larger females are more frequently and intensely courted. Also, females rarely show any overt response during the courtship process however they may signal by waving their tails when they are ready to copulate. (Shetty and Shine, 2002)

• Mating System
• polyandrous

The breeding cycle for Laticauda colubrina varies geographically. In some populations, such as those in the Philippines, the breeding is aseasonal. However, in other populations of Laticauda colubrina, like those in Fiji and Sabah, it is seasonal with the main mating period occurring during the three month period from September to December. In these populations, the eggs typically hatch from June to August. Like other species of Laticauda, these sea kraits are oviparous and return to land to lay their eggs. However, their clutch size is also subject to geographical variation. For example, clutch size has been reported as 4 to 10 in Fiji and 14 to 20 in New Caledonia. Gestation period has been difficult to document because of asynchronous breeding in many populations of Laticauda colubrina. Also, little has been researched and understood in regards to hatchling sea kraits. Their average birth mass and time to independence is unknown and requires further research. (Cox, et al., 1998; Gorman, et al., 1981; Heatwole, 1999; Shetty and Shine, 2002)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• year-round breeding
• sexual
• fertilization
• oviparous

• Breeding interval

  The breeding interval of banded sea kaits varies between seasonally or aseasonally depending on geographic location.

• Breeding season

  Some populations of banded sea kaits are aseasonal and have no specific breeding interval. Populations in Fiji breed seasonally from September to December or January.

• Range number of offspring

  4 to 20

• Range age at sexual or reproductive maturity (female)

  1.5 to 2.5 years

• Average age at sexual or reproductive maturity (male)

  1.5 years

Parental investment for banded sea kraits has not been researched and is not known. Females lay eggs on the shore but it is unclear if they return to the sea or stay on shore to care for their eggs. It has been documented that females tend to spend more time on land than males do, but hypotheses of whether this is due to parental investment or a different, unrelated cause has not been tested. More research is required to determine by what modes and to what extent, parents care for their young in this species. (Heatwole, et al., 2005)

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female

Lifespan/Longevity

The lifespan and longevity of banded sea kraits in the wild is unknown. However, it has been suggested that sea snakes generally exhibit a relatively high rate of mortality especially in their young. It is unknown if this trend is upheld in this species. In captivity, sea snakes have proven to be difficult to maintain and often refuse food, become anorexic, and die in a short time due to variety of known and unknown causes. In at least one case study, some of the known causes of death in captive Laticauda colubrina were sepsis secondary to a necrotizing enteritis or pneumonia, multi-organ granulomas and sepsis, and multicentric lymphoid neoplasia with secondary sepsis. These are some problems that cause limited lifespan for the banded sea krait in captivity and, because of this, the species is rarely kept in institutions in the United States. (Chinnadurai, et al., 2008)

Behavior

Banded sea kraits have a paddle-like tail that moves back and forth to propel it in the water. When on land, sea kraits adapt to a typical serpentine form of locomotion on firm surfaces. Interestingly, when it encounters loose substrates such as dry sand it conforms to a "side-winding" motion similar to that of many desert species of terrestrial snakes.

Because it hunts eels in the water, the banded sea krait has developed special diving adaptations including a rearward extension of the lung known as the saccular lung. This extension expands lung volume compensating for the limited volume of a tubular lung necessitated by the body shape of a snake. During inhalation, stale air in the lung moves into the saccular lung so that vascular surfaces in the lung can contact fresh air. This mechanism leads to prolonged submergence time. (Heatwole, 1999)

Although it is established that banded sea kraits are amphibious creatures, spending time both on land and in sea, the amount of time spent in both mediums is not firmly agreed upon. Some have estimated that they spend about 25% of their time on land, but more recent reviews conclude that they spend about half of their life in each medium.

The majority of their activity occurs at night or at dusk but they are not usually classified as out-right nocturnal animals. During the day, they often congregate in small groups seeking shelter in rock crevices, tree roots, tree holes, and under beach debris. They typically alternate periodically from shade to sun in order to thermoregulate. (Heatwole, et al., 2005)

• Key Behaviors
• terricolous
• natatorial
• nocturnal
• social

Home Range

Large numbers of banded sea kraits often congregate in high concentrations at specific, on-shore resting sites. However, they typically disperse over a wider range of coral reef and coastline in search of food. Unfortunately, the specific size of their home range has not been well researched. (Heatwole, 1997)

Communication and Perception

Banded sea kraits have eyes and nostrils and can locate and identify prey by smell. In general, sea kraits and true sea snakes have well-developed eyes and Jacobson's organs but lack the heat-sensing organs found in some terrestrial snakes. Also, one study researching the reproductive behavior highlighted the vomeronasal system as a critical part of communication between males and females during reproductive processes. Contact pheromones provide the most critical cues for courtship. Males follow the trail of a female in order to court the female. Also, tongue-flicking was noticed and may be a visual communication cue. The lipid composition in the skin of conspecific males and females differs between sexes and potentially provides another cue for species and sex recognition. (Heatwole, et al., 2005; Shetty and Shine, 2002)

• Communication Channels
• visual
• tactile
• chemical

• Other Communication Modes
• pheromones

• Perception Channels
• visual
• tactile
• chemical

Food Habits

Banded sea kraits are considered feeding specialists. Regardless of geographic location, they have a diet consisting almost entirely of eels of the order Anguilliform and families Congridae, Muraenidae, and Ophichthidae. Females and males typically differ in their food habits leading to the sexual dimorphism in the species. Females are typically larger and eat larger conger eels. Males usually feed on the smaller moray eels.

Sea kraits use their elongate bodies and small heads to probe cracks, crevices, and small openings in the coral matrix in order to forage for eels. They have venomous fangs and their venom contains powerful neurotoxins that affect the muscles of the diaphragm of its prey. Upon injection, these neurotoxins act rapidly, drastically impairing the swimming and breathing capabilities of an eel and making it easy to subdue. After a meal, the swimming ability of the banded sea krait is impaired and it must immediately return to land to digest its prey or else be vulnerable to predators in the water. (Glodek and Voris, 1982; Heatwole, 1999; Shine, et al., 2002; Ineich, et al., 2007)

Although often described as strictly eel-eaters, examples of other types of bony fish of the families Synodontidae and Pomacentridae have been recorded from the stomachs of some Laticauda colubrina. (Gorman, et al., 1981)

• Primary Diet
• carnivore
  • piscivore

• Animal Foods
• fish

Predation

Although not much has been reported regarding specific predators of Laticauda colubrina, known predators for many sea kraits include sea eagles (Haliastur indus and Haliaetus leucogaster) and sharks, especially tiger sharks (Galeocerda cuvieri). Also, more unusual predators have been observed, including the attack and feeding of a portunid crab on one Laticauda colubrina. Anti-predator adaptations have been documented in g. Laticauda. For one, sea kraits seek cover in crevices or amidst plants on land to digest their food after foraging. This is because their swimming ability is drastically impaired after a meal, leaving them vulnerable to sharks. Also, the banded sea krait, like many other species of sea krait, are highly venomous. It uses this characteristic in a remarkably innovative anti-predator adaptation in which the tail of the krait is rotated so that it resembles a second head. As noted above, the physical description of the head and tail of the banded sea krait is very similar. In this way the sea krait can trick a predator into thinking it has two dangerous, venomous heads and therefore serve as a preventive, mimetic adaptation. This is especially important because they spend much time probing crevices for food, leaving them exposed to attack from behind. Using this type of mimetic defense the banded sea krait can hunt without being overly vulnerable to predators. (Brischoux, et al., 2007; Heatwole, 1999; Lading, et al., 1991; Rasmussen and Elmberg, 2009; "Venomous Sea Snakes Play Heads Or Tails With Their Predators", 2009)

• Anti-predator Adaptations
• mimic

• Known Predators

  • Crabs Portunus
  • Sea Eagles (Haliastur indus)
  • Sea Eagles (Haliaetus luecogaster)
  • Sharks
  • Tiger Sharks (Galeocerda cuvieri)

Ecosystem Roles

Banded sea kraits are known hosts to endoparasitic chigger mites of the family Trombiculidae. Studies have found that larger, older snakes in Singapore contain larger numbers of mites with the maximum number of mites found in one snake being 60. These mites were found strictly within the trachea. However, the chiggers have also been found in the lung sacs in Laticauda colubrina of Taiwan. There are also known to be subject to nematodes, trematodes, and cestodes. (Chinnadurai, et al., 2008; Heatwole, 1999; Nadchatram, 2006)

Also, as banded sea kraits strictly prey on eels, they certainly play a role in controlling eel population in the coral reef ecosystems they inhabit. While they feed on eels, they may also be vital to the survival of one species of eel, banded snake eels (Myrichthys colubrinus). This eel species in the Indo-Pacific looks very similar to the banded sea krait and appears to mimic its behavior. Therefore, the eel may use this as a defense strategy, appearing as a dangerous and venomous animal to predators. (McCoy, 1980)

Economic Importance for Humans: Positive

Although the economic importance specific to banded sea kraits is not referenced, it has been noted that Laticauda sea kraits have a variety of uses. For example, the skins of a variety of Laticauda have been used for leathercraft and sold in the Phillipines since 1930. The Japanese increased the demand for sea kraits when they began commercially importing them from the Philippines and exporting them to Europe as "Japanese sea snake leather". In the Ryukyu Islands of Japan and some other Asian countries the eggs and meat of sea kraits including species of Laticauda are consumed as food. Also, the venom of many snakes may have biomedical applications both in treatment and research. They are also an important part of various coral reef ecosystem and therefore play a role in the ecotourism of some of the islands and countries in which they are located. (Heatwole, 1999; Ineich, et al., 2007)

• Positive Impacts
• food
• body parts are source of valuable material
• ecotourism
• source of medicine or drug
• research and education

Economic Importance for Humans: Negative

Although banded sea kraits are venomous they are extremely reluctant to bite humans even when provoked. They have been known to enter human residences and boats and some bites due to Laticauda colubrina have been documented. However, these attacks are extremely rare and there have been no recorded human fatalities due to this species. (Heatwole, 1999; Heatwole, et al., 2005)

• Negative Impacts
• injures humans
  • bites or stings
  • venomous

Conservation Status

Laticauda colubrina is not listed on any of the databases of endangered species indicating that the conservation status of the species has not been documented and is unknown. However, because many Laticauda species aggregate on land they are highly vulnerable to capture. Commercial harvesting, human-induced reduction of habitat in mangrove swamps, industrial pollution of coral reefs and other coastal areas, and overfishing are all environmental hazards that negatively affect the biodiversity and population size of many species of sea snakes. Some researchers have proposed that rainfall and the availability of freshwater may be determining factors in many populations of sea snake species including Laticauda colubrina. To maintain a proper water balance, they drink fresh water or very dilute brackish water in order to counteract the dehydration they experience on land and in salt water. Therefore, the population dynamics of some species of Laticauda may be affected by drought and global climate change. (Heatwole, 1999; Lillywhite, et al., 2008; Lillywhite, 2008)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• CITES

  No special status

Contributors

Eric Wright (author), University of Michigan-Ann Arbor, Phil Myers (editor), University of Michigan-Ann Arbor, Rachelle Sterling (editor), Special Projects.

References

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