Disfribuiion and Idenfificafion of Poisonous Sea Snakes 



INTRODUCTION 



The se<a snakes comprise a gi'oup of some 50 

 species all of which liave strongh- flattened 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 dis- 

 tinguish 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 ele- 

 phant-trunk snakes have only small juxtaposed 

 scales. Eels are fretjuently 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 

 GillHM't islands). One species, the pelagic sea 

 snake (PeJamJ-s), occurs far out into the o]ien 

 ocean ranging across the Pacific to the western 

 roasts of Central and South America and south 

 to New Zealand and the Cajie of Oood Hope. Xo 

 sea snake is found in the Atlantic, although the 

 ]ielagic sea snalce m;\y eventually find its way 

 through the Panama Canal and become estab- 

 lished in the Caribbean. The greatest iuunl)ers 

 of both species and individuals are found in 

 warm shallow waters without surf or strong cur- 

 rents. Mouths of ri\ers, bays, and mangrove 

 swamps are especially favored. Afany species of 

 sea snakes enter brackish or fresh water occa- 

 sionally; 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 Phil- 

 ippines 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 weathei", and 

 some species aggregate there in vast numbers. 

 The reasons for this behavior are unknown, but 

 they may l)e related to breeding. 



There are reports of both diurnal and noc- 

 turnal 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 dui'ing the monsoon storms. Their 

 young are born in these swamps. Sea snakes 

 feed largely upon fish. Eels ai'e a favorite food 

 of several species. At least a few species eat 

 jjrawns and one species feeds on fish eggs. 



Sea snakes are generally mild tempered rep- 

 tiles, although both individual and s]iecies varia- 

 tion exists with respect to this trait. In open 

 water they either seek to escape or remain almost 

 inditTerent to swimmers. Stranded on l)eaches, 

 some species are almost totally helpless. Others 

 crawl with varying degrees of facility. None can 

 strike on land l>ut most can turn to make an 

 awkward snajiping bite. Rites are usually seen 

 when the snakes are s]ai>iied, kicked, or trodden 

 u])on in shallow water or when they are removed 

 from nets, tiaps. or other fishing gear. 



Some kinds of sea snakes are extensively used 

 for luunan food in China, Japan, and parts of 

 Polynesia. 



While some sea snake species can be identified 

 I'eadily l)y 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 vari- 

 ation 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 



