SMELL — FIELDWORK AND EXPERIMENTS lOI 



tongue quickened its movements and I saw, just ahead of 

 it, what at first looked Hke a dead field vole. The adder 

 moved right up to it and was just about to seize it, when I 

 made a movement and firightened the snake away. I picked 

 up the vole which was still warm, and I could see the tiny 

 punctures where the adder's fangs had originally pierced the 

 skin just behind the head. The vole died in my hands and 

 I still have its body preserved in my collection as a souvenir 

 of a most interesting observation. 



It may be of use if I explain what probably happens on 

 these occasions. It must be remembered that snakes do not 

 always strike home accurately, and they are not always fully 

 venomed. In any case, a mouse or a vole, if not instantly 

 seized or if not paralysed at once, will bite at an aggressor. 

 Therefore an adder first of all disables the victim and does 

 not at once try to swallow it. If the venom is at its peak and 

 the victim lies helpless and still, the snake will stay where it 

 is and will only take the prey into its mouth when there is 

 no marked movement. In the first instance I have described, 

 the adder would almost certainly have located the vole 

 again — even if it had gone down a hole ; in the second case, 

 had I not intervened in order to obtain a unique specimen, 

 the vole would have been quickly taken and then swallowed. 



Experiments of a similar type may be carried out with 

 captive snakes and lizards. As is well known, our Grass 

 Snake lives on frogs, toads, newts, and small fish; and this 

 species of snake feeds readily in captivity once it has settled 

 down. If such a snake is fed regularly for a time, and is then 

 deprived of food for, say, a week (this will not harm the 

 snake) it will be keen to feed again and the hunger induced 

 by its fast will cause its senses to be sharpened. 



Remove the snake from its tank or vivarium and place it 

 where it cannot see what is happening in its usual quarters. 

 Then get a frog or toad — a toad is best, since it leaves more 

 scent — and grasping it firmly but gently, rub it in the sand 

 or earth on the bottom of the tank. You can also let it move 

 around a little on its own, but take care to note the route 

 taken. Remove the toad and put it away out of sight. Re- 

 place the grass snake which, if tame, will not take long to 

 calm down again. 



