Yellow-bellied Sea Snake

The yellow-bellied sea snake, as the name implies, has a distinctive bicolor pattern with a yellow underbelly and brown back, making it easily distinguishable from other sea snake species. Yellow-bellied sea snakes, like many other species of sea snake, are fully adapted to living their whole lives at sea: mating, eating and giving birth to live young (ovoviviparous). Adaptations to aquatic life include the reduced ventral scale size, laterally compressed body and paddle-tail for swimming, valved nostrils and palatine seal for excluding seawater, and cutaneous gas exchange for prolonging dive times. Yellow-bellied sea snakes have semi-permeable skin which extracts oxygen from the seawater through a process of cutaneous respiration while diving and swimming at the surface of the water. Sea snakes also have a special salt gland located in the lower jaw that was formerly believed to filter out salt from the surrounding seawater but has been found not to be used for that purpose, as sea snakes drink fresh water only. See snake scales for terminology used here

Morphology. …

The yellow-bellied sea snake is one of the most widely distributed snakes in the world. It is completely pelagic and is often observed on oceanic drift lines, using surface currents and storms to move around the ocean. Their distribution appears to be largely determined by favourable water temperatures, oceanic currents and recent formation of land bridges that have blocked farther dispersal.

The yellow-bellied sea snake has an extensive distribution covering the entire tropical Indo-Pacific, as well as extending to Costa Rica, southern California, and northern Peru. It is the only sea snake to have reached the Hawaiian Islands. The favoured habitat for hunting and reproduction includes free floating mats of sea kelp occurring in the Indian Ocean. The species is the most commonly beached sea snake on the coast of Southwest Australia, including records at beaches near metropolitan areas. It is also reported from Christmas Island and Cocos (Keeling) Islands (Australia). The yellow-bellied sea snake requires a minimum of 16–18 °C (61–64 °F) to survive, long-term. However, the species has been reported in colder waters of the Pacific, such as the coasts of southern California, Mexico, Tasmania, and New Zealand, the latter being a country that would otherwise be free of snakes were it not for the infrequent strandings of yellow-bellied sea snakes and banded sea kraits. …

Contrary to past beliefs, sea snakes require fresh or brackish water to survive; the yellow-bellied sea snake likely drinks mainly from freshwater lenses that form on the surface of the sea after heavy precipitation. This species has been reported to survive severe dehydration of up to 7 months during seasonal drought. Yellow-bellied sea snakes breed in warm waters; they are ovoviviparous with a gestation period around 6 months. According to Ditmars, females bear live young in tidal pools. They move poorly on land due to their smaller belly scales that form a ventral keel. They are sometimes observed in large aggregations of thousands on the surface of the water in oceanic drift lines, which has been proposed as a strategy to catch prey. They hunt by floating on the surface of the water to attract pelagic fish that are seeking shelter; prey are captured via a backwards swimming motion and rapid lunge of the jaws. The ability to swim backwards is an unusual and distinguishing characteristic of this species. Heatwole proposed that these snakes find their prey by sensing the vibration generated by fish movement. These snakes are not considered aggressive but will defend themselves if threatened.