Distribution and Identification of Poisonous Sea Snakes INTRODUCTION The sea snakes comprise a group of some 50 species all of which liave stronghflattened oar-like tails used as sculls. In addition most species have nostrils opening on the top of the head, a body that is flattened from side to side, and very small ventral scutes that may be difficult to distinguish from the adjoining scales. The scales of several kinds of sea snakes are juxtaposed rather than overlapping as in most land snakes. The only snakes likely to be confused with sea snakes are the elephant-trunk snakes (Acrochordus) and the river snakes E7ihydris and others) ; these liave round or slightly flattened tails, but young elephant-trunk snakes liave tails as paddle-shaped as those of some sea snakes. However, all sea snakes have enlarged crown shields and the elephant-trunk snakes have only small juxtaposed scales. Eels are frequently confused with sea snakes; however, no sea snake has fins or gill openings, and none has a smooth skin without scales. Sea snakes are reptiles essentially of south Asian and Australian coastal waters with a few species found well out into Oceania (Society and Gillhmt islands). One species, the pelagic sea snake (Pejamj-s), occurs far out into the open ocean ranging across the Pacific to the western roasts of Central and South America and south to New Zealand and the Case of Good Hope. Xo sea snake is found in the Atlantic, although the pelagic sea snake my eventually find its way through the Panama Canal and become established in the Caribbean. The greatest iuunlers of both species and individuals are found in warm shallow waters without surf or strong currents. Mouths of rivers, bays, and mangrove swamps are especially favored. Many species of sea snakes enter brackish or fresh water occasionally; two species are restricted to lakes. The biology of sea snakes is poorly known. There is general opinion that they can remain submerged long periods — perhaps a few hours depending upon temperature, degree of activity, and other factors. The depths to which they can dive are also unknown. An observer in the Philippines saw the snakes swim down out of sight in very clear water. Types of bottom dwelling fish found in stomachs indicate the snakes dive at least 20 to 30 feet to capture food. They are often seen at the surface in calm weather, and some species aggregate there in vast numbers. The reasons for this behavior are unknown, but they may le related to breeding. There are reports of both diurnal and nocturnal activity. In the Arabian Sea, some species range 10 to 20 miles off shore during the calm winter months but tend to seek coastal mangrove swamps during the monsoon storms. Their young are born in these swamps. Sea snakes feed largely upon fish. Eels aie a favorite food of several species. At least a few species eat prawns and one species feeds on fish eggs. Sea snakes are generally mild tempered reptiles, although both individual and species variation exists with respect to this trait. In open water they either seek to escape or remain almost indifferent to swimmers. Stranded on leaches, some species are almost totally helpless. Others crawl with varying degrees of facility. None can strike on land lut most can turn to make an awkward snapping bite. Rites are usually seen when the snakes are sailed, kicked, or trodden uon in shallow water or when they are removed from nets, tips. or other fishing gear. Some kinds of sea snakes are extensively used for lauan food in China, Japan, and parts of Polynesia. While some sea snake species can be identified Readily ly the amateur, many are puzzling even to experienced herpetologists. Color and pattern are extremely deceptive in this family. There are close similarities between remotely related species and marked differences between young and adults of the same species as well as a good deal of variation among adults of the same species. KEY TO GENERA 1. A. Ventrals at midbody large, half to one third the width of the belly 2 B. Ventrals at midbody small or not differentiated 5 159