IUCN - Sea snakes

Sea snakes

28 February 2010 | Fact sheet

Where do sea snakes live? How do they breathe and reproduce? Why do they shed their skin?

1. Where can we find sea snakes?

Sea snakes are air-breathing cold-blooded reptiles. Like all snakes they have forked tongues and body scales and they regularly shed their skins. They are found primarily in warm tropical waters of the Pacific. The area of highest species diversity is Indonesia and northwest Australia. Each of these regions has more than 20 species but many species that occur in Indonesia and other parts of south east Asia do not occur in Australia and vice versa. Most of Australia’s tropical coastal waters have a high species diversity. The Great Barrier Reef has 14 species of sea snakes. Although sea snakes need warm tropical waters to survive, they are occasionally blown south by storms and have been recorded in Sydney Harbour.

2. How do sea snakes breathe?

Sea snakes must come to the surface to breathe. However, they can spend from 30 minutes to 2 hours diving between breaths. This is possible for two reasons: they have one elongated cylindrical lung that extends for almost the entire length of their body and they can breathe through their skin.

3. How do sea snakes reproduce?

Like all snakes and lizards, male sea snakes have two penises – hemipenes - but each one functions independently and only one is used during mating. Mating takes place under water and sea snakes must surface for air during the process. The female controls breathing and as she swims to the surface the male is pulled along attached via the hemipenis. At the surface, the male gulps for air or he has to wait till the next time the female comes up to the surface to breathe. Males are unable to disengage until mating is finished.

4. How are sea snakes born?

Most sea snakes give birth after gestation periods that range from four to eleven months, depending on the species. Most species reproduce every year. The timing of the reproductive cycle varies between species and also differs between geographical locations for the same species. Young are born underwater and must be independent immediately to swim to the surface to breathe. There is no parental care.

5. How do sea snakes shed their skin and why do they do it?

Sea snakes shed their skin every two to six weeks, which is more frequent than land snakes and more often than needed for growth alone. To shed its skin, the snake rubs its lips against coral or other hard substrate to loosen it. It then catches the skin against something to anchor it and crawls forward leaving the skin turned inside out behind it. Skin shedding allows sea snakes to rid themselves of marine organisms such as algae or barnacles. If they didn’t shed their skin, the organisms would interfere with the snakes’ ability to swim and could cause disease.

Source and more information: IUCN Sea Snake Specialist Group