308 UNDERWATER GUIDE TO MARINE LIFE 



Fig. 186. Leatherhack turtle. 



other sea turtles, and the luckv swimmer or beachcomber may see one then. If 

 so, he should not molest it but observe all he can and contact the nearest scientific 

 institution as soon as possible. This is a rare animal of great scientific interest. 



Leatherbacks are powerful and able to inflict damage with their beak and 

 flippers. Thev frequently roar or scream when molested. They probably are 

 more or less omnivorous. 



Snakes: Order Squamata 



There is one small family of sea snakes typical of the Indo-Pacific and repre- 

 sented in our seas by one species. 



SEA SNAKES: Family Hydrophidae 



These snakes live exclusively on the sea, never coming on land, except for 

 one Indo-Pacific species which comes ashore to lay eggs. They are, if placed 

 on land, almost helpless since they have lost the large, flat belly scales of most 

 snakes and cannot crawl on land except by considerable effort. But in the sea, 

 they are completely at home and are excellent swimmers. Their tails are com- 

 pressed like oars and even their bodies are a little compressed. Their nostrils are 

 placed on the top of the snout for easy access to surface air. Under water, the 

 nostrils are closed by a valve. Sea snakes are closely related to the coral snake- 

 cobra clan, all members of which possess a powerful neurotoxic poison. The sea 

 snakes may surpass even these in the drop-for-drop power of their venom, but, 

 fortunately, they are very reluctant to bite. Fishermen remove them from nets 

 with their bare hands, and these snakes are not known to attack or bite humans 

 in the water. They arc almost exclusivelv fish-eaters. They bask on the surface 

 almost motionless. Small fishes gather around them, as they would gather around 

 a floating stick, and are captured and eaten. Sea snakes inhabit shallow coastal 

 waters, particularly near river mouths, and shun the deep sea. They are ovovi\'ip- 

 arous or oviparous. At times they congregate in huge masses at the surface. One 

 such mass was reported to be 10 feet wide and 60 miles long. The reason for 

 such congregation is not known, but it mav be for copulation. When so congre- 

 gated, they lose their normal alertness and are easilv approached. 



