SEA KRAITS AND SEA SNAKE SPECIES
Belcher sea snake Most sea snake species inhabit coral reefs and live mostly off the coast of small islands. Because of this they often have a patchy geographic distribution, which is often dependant on sea currents and suitable terrestrial shelter. to true sea snakes. Because of the wide geographic distribution of sea kraits, and other snakes over widely-spaced different islands members of the same species may vary in some physical characteristics such as head shape and size. [Source: Animal Diversity Web (ADW)]
Sea kraits (Laticauda) are a genus of venomous elapid sea snakes (subfamily: Laticaudinae),. They are semiaquatic, and have wide ventral scales typical of terrestrial snakes for moving on land and have paddle-shaped tails for swimming. Unlike fully aquatic ovoviviparous sea snakes (having eggs that remain in the mother's body until they hatched)., sea kraits are oviparous (lay eggs) and must come to land to digest prey and lay eggs. The are eight recognized spies: 1) yellow-lipped sea krait (Laticauda colubrina); 2) blue-lipped sea krait (Laticauda laticaudata); 3) black-banded sea krait (Laticauda semifasciata); 4) Guinea's sea krait (Laticauda guineai Heatwole); 5) Crocker's sea snake (Laticauda crockeri); 6) New Caledonian sea krait (Laticauda saintgironsi); 7) katuali or Niue sea krait (Laticauda schistorhyncha) and 8) Laticauda frontalis. [Source: Wikipedia
Among the species found in the Philippines are: Lake Taal snake (Hydrophis semperi), pelagic sea snake (Pelamis platurus), yellow-lipped sea krait (Laticauda colubrina) and Stoke’s sea snake (Astrotia stokesii). The Philippines have one of the highest densities of sea snake populations in the world and these marine reptiles are commonly encountered in both the inshore and offshore waters throughout the archipelago. One species of sea snake, the Lake Taal snake, is the only known species to have adapted to fresh water, and lives in a flooded volcanic caldera on Luzon. The greatest numbers of sea snakes are found in warm, shallow waters, without strong surf or current, along coastlines. The mouths of rivers, bays, and mangrove swamps are especially favored. They thrive in a variety of habitats, ranging from muddy or turbid water to clear waters and coral reefs. Many species of sea snakes enter brackish or freshwater occasionally. Some species of sea snakes that inhabit the deeper ocean waters are only rarely found close to shore, when wind or currents cause beach strandings.
The olive sea snake is native to Australian waters, often found swimming among the fish on a coral reef. The snakes are some of the most common on the reef, and they are notoriously curious, often approaching divers. The olive sea snake can hold its breath for up to two hours. The snakes are mostly nocturnal and hide in holes in the reef during the day when they aren’t out hunting small fish or checking on a snorkel group. But they can be dangerous. Named for the color of their skin, olive sea snakes are venomous. Though not known to attack people, olive sea snake bites have been fatal. Some olive sea snakes can be almost 7 feet long and can swim down to depths of 230 feet below sea level. [Source: Irene Wright, Miami Herald, February 10, 2023]
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures
Banded Sea Krait
The banded sea krait (Scientific name: Laticauda colubrina) is also known as the yellow-lipped sea krait and Colubrine sea krait. It is the most widely distributed of the Laticauda genus, which includes related species such as the New Caledonian sea krait (Laticauda saintgirosi).[Source: Eric Wright, Animal Diversity Web (ADW) /=]
The banded sea krait is found in the Pacific Ocean and Indian Ocean. Particularly associated with northern Papua New Guinea and the Solomon Islands and mainly found in waters off of Australia, Asia and around some Pacific islands. It lives in tropical, saltwater and marine environments and is often found in reefs, intertidal zones and other coastal areas at depths of 0 to 60 meters (0 to 197 feet) at an average depth of less than 20 meters (65.6 feet).
These snakes often hide in small crevices or under rocks and favors reefs where their primary food source — eels — make their home. They are usually in the ocean butoften spend between 25 and 50 percent of their life in rocky islets, where they court, mate, lay eggs, digest food, and shed their skins. They can also be found in mangrove areas and have the ability to climb trees. They have been observed on islands, residing 36 to 40 meters (118 feet to 131 feet) above sea level.
Banded sea kraits range from the Bay of Bengal, the western coast of Thailand, Malaysia, and Singapore in Southeast Asia westward to the the Andaman and Nicobor Islands of India. They have been seen as far north as Taiwan and Miyako, Yaeyaema island and the Ryukyu Archipelago in southern Japan and as far east Palua in the northwest Pacific and Tonga in the southwestern Pacific. They are not found in the Atlantic and Caribbean oceanic regions.
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 not cause any problems. A banded sea krait bites have been documented but these are extremely rare and there has been no recorded human fatalities due to this species. Banded sea krait are not endangered. They are designated as a species of least concern on the International Union for Conservation of Nature (IUCN) Red List and have no special status according to the Convention on International Trade in Endangered Species (CITES).
Banded Sea Krait Characteristics
Banded sea kraits are so called because of their characteristic yellow upper lip. Heterothermic (having a body temperature that fluctuates with the surrounding environment) and venomous, they have an average weight of 0.6 to 1.8 kilograms grams (1.3 to four pounds) and range in length from 75 to 360 centimeters (29.5 to 141.7 inches), with their average length being 125 centimeters (49.2 inches). Both sexes are roughly equal in size and look similar. Females are larger. [Source: Eric Wright, Animal Diversity Web (ADW) /=]
According to Animal Diversity Web: 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.
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. /=\
Banded Sea Krait Behavior, Perception and Communication
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.. It has not been established how much time they spend on land.Some have estimated that they spend about 25 percent of their time on land, but more recent reviews conclude that they spend about half of their life there. The majority of their activity occurs at night or at dusk but they are not regarded as full-fledged nocturnal animals. During the day, they often congregate in small groups sheltered in rock crevices, tree roots, tree holes, and under beach debris. They typically alternate periodically from shade to sun in order to thermoregulate.. [Source: Eric Wright, Animal Diversity Web (ADW) /=]
Banded sea kraits communicate with vision, touch and chemicals usually detected by smelling. They also employ pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species) and sense using vision, touch and chemicals usually detected with smell. /=\
According to Animal Diversity Web (ADW): 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 (chemicals released into air or water that are detected by and responded to by other animals of the same species) 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. /=\
Banded Sea Krait Food and Eating Behavior
Banded sea kraits are considered feeding specialists Although often described as strictly eel-eaters, examples of other types of fish been recorded from the stomachs. According to Animal Diversity Web: Regardless of geographic location, they have a diet consisting almost entirely of eels of the order Anguilliform and families Congridae (conger eels), Muraenidae (moray eels) and Ophichthidae (snake eels). [Source: Eric Wright, Animal Diversity Web (ADW) /=]
According to Animal Diversity Web: 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. /=\
Some have suggested that sexual dimorphism (differences between males and females) found in the species is the result of differences between male and female feeding patterns, with the larger females feeding on a larger deep-water species of eels such as conger eels while the male feed on smaller eels that inhabit shallow water such as moray eels. /=\
Banded sea kraits are also believed to be vital to the survival of one species of eel, the banded snake eel (Myrichthys colubrinus). This eel species looks very similar to the banded sea krait and appears to mimic its behavior — saying to predators I am a dangerous and venomous creature.
Banded Sea Krait Mating, Reproduction and Offspring
Banded sea kraits are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). They engage in seasonal breeding and year-round breeding. The number of offspring ranges from four to 20. Females reach sexual or reproductive maturity at 1.5 to 2.5 years. On average males reach sexual or reproductive maturity at 1.5 years. [Source: Eric Wright, Animal Diversity Web (ADW) /=]
Banded sea kraits are polyandrous, with females mating with several males during one mating season. According to Animal Diversity Web: 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. /=\
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 percent were a male and female pair, and the remainder involved a female and two to nine 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. /=\
The breeding interval varies between seasonally or aseasonally ( not occurring during or limited to a particular season) depending on geographic location. Populations in Fiji and Sabah breed seasonally from September to December or January. In the Philippines, breeding is aseasonal. Among Fiji and Sabah populations, the eggs typically hatch from June to August.
Pre-fertilization provisioning and protecting is done by females. Eggs are laid on land near the sea. 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.
The Leaf-scaled Seasnake (Scientific name:Aipysurus foliosquama) has a presumed life span of eight to 10 years, relatively long for snake and believed to be compensate for the long time that the reptile take to reach sexual maturity. The snake is endemic to three known places: 1) the Ashmore Reef and 2) the Hibernia Reef in the Timor Sea off the northwestern coast of Australia and 3) and Shark Bay off western Australia. Leaf-scaled seasnake are typically found at depths of zero to 10 to meters (0 to (32 feet). They prefer the shallow areas along the edges of reefs. The relatively recently discovered population of Shark Bay lives in the sea grass beds. [Source: Molly Schools, Animal Diversity Web (ADW) /=]
Leaf-scaled seasnakes feed primarily on shallow reef dwelling fish such as wrasses and sleeper gobies. In addition, they eat certain types of eels which are found in the same shallow, reef habitats. The snakes find prey by sticking their head into holes and crevices in coral reefs. They then bite and immobilize prey with their venom. Leaf-scaled seasnakes are regarded as top predators and may play a role in the population control of the species that it eats. The snake shed its skin frequently — once every two to six weeks — as a countermeasure against algae and barnacles which use the snake as a host.
Leaf-scaled seasnakes are listed as critically endangered on the ICUN Red List. This is dure primarily to the fact they are found in such a limited range. The venom of the leaf-scaled seasnake is potentially fatal to humans. Reported cases of bites are rare.
Leaf-Scaled Seasnake Characteristics, Mating and Behavior
Leaf-scaled seasnakes were named for the shape and pattern of their closely overlapping scales, which resemble leaves. venomous. They weigh up to half a kilograms (1.1 pounds) and range in length from 60 to 90 centimeters (23.6 to 35.4 inches). Females are larger than males. Both sexes are similar in appearance. The dorsal side is often dark reddish brown to purple, with lighter bands down the back females often tend to be larger than their male counterparts. [Source: Molly Schools, Animal Diversity Web (ADW) /=]
Leaf-scaled sea snakes are solitary creatures with the exception of mating and occasional sightings of small groups The three known populations of Leaf-scaled seasnake are believed to represent three largely isolated breeding populations separated by large stretches of open ocean waters that are difficult for individuals to cross.
Leaf-scaled seasnakes communicate with vision, touch and chemicals usually detected by smelling, pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species) and vibrations and sense using vision, touch, vibrations and chemicals usually detected with smell.
Leaf-scaled seasnakes are viviparous (give birth to live young that developed in the body of the mother), iteroparous (offspring are produced in groups) and Leaf-scaled seasnakes may breed less than once a year. The gestation period ranges from six to seven months. On average males and females reach sexual or reproductive maturity at age two years.
Fertilization is internal, and males have hemipenes which are used during mating. The male and female entwine during mating, which involves the snakes having to come to the surface for air multiple times. The female snake seems to determine when the mating pair takes breaths of air and when the mating process is concluded. During the pre-fertilization and pre-birth stages provisioning and protecting is done by females.
Yellow-Bellied Sea Snake
Yellow-bellied sea snake (Scientific name: Pelamis platura) is also known as the pelagic sea snake. It reaches a maximum length of 1.13 meters (3.7 feet) and s is the only sea snake that occurs on both sides of the Pacific and in the Hawaiian Islands. The snake has been observed in the Indian and Pacific oceans around eastern Africa, Madagascar, Arabia, India, coastal southeastern Asia, Indonesia, Japan, Australia, New Zealand, and the Pacific Islands. In the eastern Pacific Ocean is has been seen the western coast of the Americas from Equador and the Galapagos Islands in the south to Baja California and the Gulf of California in the north. [Source: Jennifer Liptow, Animal Diversity Web (ADW) /=]
Yellow-bellied sea snake are found in tropical and subtropical waters and are typically . They are usually found within a few kilometers of the coast and prefer shallow inshore waters. These hardy snakes live in waters with temperatures that range from between 11.7 and 36 degrees Celsius (53 to 97 degrees F). These snakes are not currently listed as Endangered or threatened. The IUCN) Red List lists them as a species of least concern. They are poorly suited for land and are relatively helpless when washed ashore. They have mild-mannered temperament and sometimes occur in huge aggregations, with varying male to female ratios, numbering in the thousands. /=\
Yellow-bellied sea snakes are venomous snakes. Their venom is neurotoxic and a fairly small amount is delivered with a bite. No human fatalities have been reported. For food, the snake forages during the day, hunting by ambushing its prey, chewing poison into fish and then swallowing them. /=\
Yellow-bellied sea snakes feed during the day and spend nights on the ocean bottom, occasionally rising to the surface to breath. According to Animal Diversity Web: They can dive to maximum depths of 6.8 meters in the dry season, and 15.1 meters during the wet season. They can stay underwater for between 1.5 and 3.5 hours. It swims on the surface by sideward undulations aided by the laterally compressed tail, which acts as a paddle. It can move quickly, but usually it floats by ocean currents. This snake reproduces sexually in water, usually near the surface in water with a temperature greater than 20 degrees Celsius. This species is ovoviviparous (eggs are hatched within the body of the parent) and the gestation is thought to be five to six months. One to 10 young are born per litter, with each one around 2.2-2.6 centimeters (around an inch) long at birth. Adult males grow to greater than 60 centimeters (two feet). /=\
Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated March 2023