gS THE SENSES OF ANIMALS 



unusual way. The action performed may be just what is done 

 in the wild ; but changed conditions bring about a kind of 

 "substitute behaviour" that seems wrong or misleading, 

 although it is really perfectly normal if observed with 

 some background information regarding basic wild behav- 

 iour. 



As an example of what I mean, let me refer to experiments 

 in the intelligence of rats, one test of which is to construct 

 a maze through which the rat has to find its way accurately 

 and repeatedly in order to obtain a "reward" in the shape 

 of food, the time taken to learn the correct route being con- 

 sidered indicative of the rat's intelligence. 



I well remember discussing this "test" with an experi- 

 menter. I asked him if the mazes were used frequently on 

 the same rat, and I was told that this often had to be done 

 due to lack of space in the laboratory and also expense — for 

 a number of mazes would take up valuable room and cost 

 more money. I then asked whether the cages were cleaned 

 out each time an experiment was made in order to exclude 

 the possibility of scent being the real cause of the rat's success. 

 The reply was that not only were the cages cleaned out, but 

 that they were scrubbed with hot water. 



This, I fear, did not convince me, because much experience 

 has taught me that it is difficult in the extreme to eliminate 

 traces of mammal scent however much one scrubs. Consider 

 the domestic dog: few dog owners have not had the ex- 

 perience of "accidents" occurring in their houses — either 

 when their own dog is in the process of being trained or 

 when a visiting dog (not yet house trained) has performed 

 a natural function on the carpet or against a convenient 

 chair ! Now, no matter how well the carpet or chair cover 

 is cleaned, it is a fair bet that, even months after the accident, 

 some dog will come to the house, make straight for the 

 original spot and will mark its approval — or disapproval — 

 in the usual way. This is good proof of the persistence of 

 concentrated scent. 



Let us now consider some field observations and experi- 

 ments in connection with scent in some varying kinds of 

 animals. 



