Hydrophis platurus

Yellow-bellied sea snake

Hydrophis platurus
(Linnaeus, 1766)

Yellow-bellied sea snake (Costa Rica). credit: Aloaiza <a href="https://creativecommons.org/licenses/by/3.0/">CC BY 3.0</a>
Image attribution
Yellow-bellied sea snake (Costa Rica). photo credit: Aloaiza CC BY 3.0
Herpetofaunal category
Marine Reptiles
Species complex
Conservation Status
Not Threatened
Common names
Yellow-bellied sea snake,
Yellowbelly sea snake,
Pelagic sea snake.

LengthFemales up to 1.1 m; males 0.7 m.



A beautiful marine snake exhibiting striking bicolour patterning consisting of black upper surfaces, contrasted by bright yellow lower surfaces. The black dorsal stripe present on the body breaks up towards the paddle-like tail, which is yellow with black spots.
It is by far the most commonly observed marine snake in New Zealand.



Unlikely to be confused with the marine kraits that reach New Zealand due to its striking black, and yellow colouration, and drastically different body morphology.


The yellow-bellied sea snake is the world’s most widespread snake species occurring throughout the warm tropical pelagic waters of the Indian and Pacific oceans. New Zealand is the southernmost limit for this species in the western Pacific, with individuals recorded as far south as Wellington and Westport. It is possible that this species is resident year-round in the warm waters around the Kermedec Archipelego, but there is little evidence of this.


Primarily feeds on fish and cephalopods.

Ecology and Habitat

A fully-aquatic, diurnal species, that spends its entire life at sea. They are often found in association with large drift lines of flotsam that occur in the convergence zones of the ocean, but can be found in more coastal habitats including the intertidal zone. Being a strong swimmer, this species spends around 87% of it’s time underwater, diving to depths of up to 50 metres.

Life Expectancy

Not known.

Social Structure

Solitary, but have been recorded in great numbers in the drift line communities that occur in the open ocean.

Breeding Biology

Yellow-bellied sea snakes may breed in the pelagic waters in the far north of New Zealand. They are viviparous, giving birth to 1-8 live young. Sexual maturity is reached at 500mm for males and 600mm for females.

Disease and threats

Yellow-bellied sea snakes have few predators, but are susceptible to ocean currents which may displace them to regions that are unsuitable for survival. They are host to several reptilian diseases, and parasites.
Yellow-bellied sea snakes also act as hosts for many epibionts including crabs, and barnacles.




Gill, B. J. (1997). Records of turtles and sea snakes in New Zealand, 1837–1996. New Zealand Journal of Marine and Freshwater Research31(4), 477-486.

Graham, J. B., Lowell, W. R., Rubinoff, I., & Motta, J. (1987). Surface and subsurface swimming of the sea snake Pelamis platurusJournal of Experimental Biology127(1), 27-44.

Pfaller, J. B., Frick, M. G., Brischoux, F., Sheehy III, C. M., & Lillywhite, H. B. (2012). Marine snake epibiosis: a review and first report of decapods associated with Pelamis platurus.

Vallarino, O., & Weldon, P. J. (1996). Reproduction in the yellowbellied sea snake (Pelamis platurus) from Panama: Field and laboratory observations. Zoo Biology: Published in affiliation with the American Zoo and Aquarium Association15(3), 309-314.

van Winkel, D., Baling, M., & Hitchmough, R. (2018). Reptiles and Amphibians of New Zealand: A Field Guide. Auckland University Press, pp376.