I02 THE SENSES OF ANIMALS 



Very soon you will note that the snake will flicker its 

 tongue rapidly and will quickly pick up the scent trail. It 

 will follow this faithfully, and if you have accurately noted 

 where the scent was laid, you will obtain excellent evidence 

 of the way a snake can track down prey that is not in 

 sight. 



I have had a film taken of one of my Smooth Snakes 

 following the scent track left by a lizard ; and this film made 

 me realize that unless the creature which a snake ultimately 

 eats is moving when first encountered — in which case the 

 snake will be stimulated by sight — a victim is often tracked 

 down by scent until it is finally located and seized. 



Captive lizards too may be tested in this way by laying 

 your trail with a crushed mealworm or dead moth. Most 

 lizards will follow such a trail just as accurately as a snake. 

 Our legless lizard, the Slow Worm, will do the same with 

 a slug. It will scent the slime trail left by the slug and follow 

 it up with great precision. 



Amphibians 



Frogs, toads, and particularly newts, all possess the sense of 

 smell, though in all of them sight is the principal sense used 

 in catching food. As already mentioned in the previous 

 chapter, there is some reason to think that toads may be 

 able to scent the ponds to which they go to spawn. Frogs 

 are less likely to behave in this way since they do not often 

 travel overland. They ^depend more on ditches and small 

 streams which lead to their breeding places ; in many cases 

 the frogs may breed in the ponds where they have spent the 

 winter in hibernation amongst the mud and debris at the 

 bottom. All the same, we cannot claim to know just how 

 frogs do find their way along ditches and streams, and it 

 may well be that smell also plays some part in this migratory 

 behaviour. 



Our Natterjack Toad gives off a scent from its skin when 

 irritated and this undoubtedly is a means of protection. I 

 have never known a grass snake attempt to swallow a natter- 

 jack, though the tongue will be used to "test" this little 

 toad. The odour given off by natterjacks is said to resemble 



