MIGRATION. AND HIBERNATION. 43 



The true water snake has the nostrils placed on the top of 

 the snout. 



Salt-water Snakes. 



These snakes inhabit the ocean, and feed upon fish and 

 other marine creatures. They are all very venomous. The Salt- 

 water Snakes are distinguished from all other snakes in having a 

 keel-like tail, flattened at the sides, which they use as a propeller. 

 They possess no fins and are true snakes, and therefore real sea 

 serpents. They are all ovo- viviparous, and the gravid female 

 visits the shallow waters of rocky coasts and gives birth to her 

 young in the rock pools. Sea snakes are usually brilliantly 

 coloured. They are seldom found in mid-ocean. Some attain 

 a length of six feet. Their venom has an almost instantaneous 

 fatal effect on fish. 



Migration and Hibernation. 



Snakes do not migrate from one locahty to another, unless 

 forced by hunger or a change in their surroundings, such as an 

 unusually heavy rainfall, rendering the ground more or less 

 marshy, or the slow change brought about by the prolonged 

 droughts which occur from time to time in various districts. 

 They always remain in the same locality as long as food is pro- 

 curable. Most species have some favourite spot to which they 

 retire when desiring to rest, or to escape from their enemies. 



Snakes hibernate during the colder months of each year. 

 They do this for two good reasons. Food is scarce during 

 the winter months. Snakes are largely dependent for their 

 vitaUty on the temperature of the surrounding air, their bodies 

 being unable to accommodate themselves to rapid changes of 

 temperature owing to the very slow circulation of their blood 

 and consequent low normal temperature. In the tropics and in 

 favourable situations in temperate climates, snakes often remain 

 active all the year round. In certain localities in South Africa 

 several species of snakes do not hibernate. Others hibernate 

 only when the days are very chilly, but if a warm breeze should 

 blow, and the temperature of the air rises a few degrees, they 

 will often issue out of their lurking places to bask in the sunshine. 

 I have examined snakes quite stiff and rigid, and apparently dead 



