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. 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). 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. Nonetheless, these wayward individuals make the yellow-bellied sea snake the most commonly-seen snake (and sea snake) in New Zealand, to the degree that the species is considered
native (indigenous) to New Zealand and worthy of protection under the
Wildlife Act 1953. These colder water occurrences are believed to be linked to
El Niño, among other severe weather events, possibly creating unusually strong, new ocean currents that transport the snakes far off-course. In October 2015, a beached yellow-bellied sea snake was reported and photographed in
Ventura County, California, well outside its normal range, for the first time in 30 years. A few months later, in January 2016, a stranded individual was found in
Coronado, California, washed-up on Coronado Beach's north end (better known as Dog Beach), just south of
Naval Air Station North Island (NASNI). The specimen was subsequently transported to and examined at the
Scripps Institute of Oceanography,
La Jolla. The yellow-bellied sea snake is the only sea snake to have been found in the Atlantic Ocean, although only in limited circumstances. The yellow-bellied sea snake's occurrence into the Atlantic is not considered a part of its native range, but rather a dispersal from its native Pacific range. The yellow-bellied sea snake has been found in all the countries of
Africa's eastern coast and all eastern islands, like Djibouti, Eritrea, Kenya, Madagascar, Mauritius, Mayotte, Mozambique, Réunion, Seychelles, Somalia, South Africa and Tanzania. The yellow-bellied sea snake has also been found in the
Colombian Caribbean four separate times, making it the only sea snake to be found in the
Caribbean Sea. However these occurrences are believed to be the result of human activity, be it ship discharge, intentional release or via the
Panama Canal, as it is not considered a part of their native range. This is due to the
land bridge between North and South America, the
Isthmus of Panama, which formed from about 10 million years ago to 3 million years ago (i.e.,
continental drift), acting as a
dispersal barrier and preventing entry into the Caribbean Sea from the Pacific Ocean. The man-made
Panama Canal has not made a crossing of the isthmus possible presumably because it is
fresh water. Due to the wide distribution of the species and relative lack of
dispersal barriers, it has been assumed that individuals from different localities represent a single breeding
population (i.e., high
gene flow). However, a study that used
haplotype networks in two populations from
Costa Rica suggests that shallow genetic population structure exists, which reflects variation in colour patterns (brown and yellow in
Golfo de Papagayo and completely yellow in
Golfo Dulce). ==Behaviour==