The diet of the bar-bellied sea snake is reported to include squid, bottom-dwelling fish (1) (2) and eels (2) (3) (8). However, some studies suggest that, like other Hydrophis species, the bar-bellied sea snake may be a specialist predator, feeding only on eels (12) (13) (14) (15).
Despite being an air-breathing animal, the bar-bellied sea snake is capable of remaining underwater for up to two hours at a time, before surfacing to breathe again. Its single, elongated lung, which extends for almost the entire length of its body, is highly efficient for gas exchange, and sea snakes are also able to absorb oxygen through their skin when underwater. As in other sea snake species, the bar-bellied sea snake has specialised valves which block off its nostrils while underwater (2).
Living in the marine environment poses several other challenges, and like other sea snake species, the bar-bellied sea snake has a specialised gland under its tongue which enables it to excrete excess salt from its body. A sea snake sheds its skin approximately once every two to six weeks. By shedding its skin so frequently, a sea snake can get rid of the many marine species, such as algae and barnacles, which become attached to it (2).
Like most species of sea snake, the bar-bellied sea snake is viviparous (2) (5) (8) (15), meaning that it gives birth to live young rather than laying eggs (2). This species appears to reach sexual maturity at about two years old (2) (16), and females are thought to only breed every two to three years (1) (2) (16), although they may potentially breed every year (2).
Mating in sea snakes is a lengthy affair, and the males are unable to disengage from the female until copulation is complete (2). In northern Australia, mating takes place between early May and the end of July (2) (16). Although young are born in February in this region, bar-bellied sea snake births occur between March and May in southeast Queensland. Some studies suggest that the bar-bellied sea snake may move into estuaries to give birth (2).
The bar-bellied sea snake is thought to produce an average of about 12 or 13 young per clutch (1) (2) (16), although clutches of up to 30 young have been reported (2). Clutch size is also known to be variable and to increase with the length of the female (1).