62 BRAIN MECHANISMS AND LEARNING 



explore the chick agahi. When it tried to escape, both chased and caught 

 it, but they showed a very strong inhibition to bite. They just seized the 

 chicks, without causing injury, and carried them into their nesting box. 

 After 5 hours the chicks were still alive there. I took them away. On each 

 of the following 7 days I offered one chick to each of these polecats. 

 During that time they were fed only with very little meat every third day. 

 Until the fourth day, the behaviour of the polecats towards the chick 

 remained nearly the same. After a short investigation they grasped the 

 chick and carried it home, uttering the call of social contact. In one of the 

 polecats a little hostility was observed on the third day; it hissed when it 

 met the chick, but soon started muttering. On the fourth day I left the 

 chicks with the polecats over night. Next morning polecat {b) had killed 

 and partly eaten its chick, while the other chick was sitting in the warm 

 nest without showing the slightest damage. A newly offered chick was 

 attacked by the polecat, grasped in the neck but with inhibition to bite, 

 and carried alive to the nest, where it was killed and eaten half an hour 

 later. Polecat ((7) however, hissed a little, then carried the new chick to its 

 nest, where I found it still ahve next morning. After I killed it, the hungry 

 polecat immediately started eating. On the same afternoon, both were 

 given chicks again; both carried them in alive. After 3 hours the chicks 

 were found to be still ahve. This time polecat {a) killed the chick during 

 the night, whereas polecat (/>) left it undamaged. The experiments are 

 not fmished yet. 



The experiments have shown that learning plays an important role in 

 the development of prey-hunting behaviour, but also that there are some 

 important inborn reactions. What is learned is the orientation of the 

 killing bite towards the neck of the prey, a learning process which takes 

 place only if the prey proves difficult to kill otherwise. The polecat has, 

 furthermore, to learn that a quietly sitting rat or chick is prey, even when 

 it has eaten dead rats or chicks before. The first attack is released by a 

 fleeing object, this reaction of chasing and biting fleeing prey is iimate, 

 as well as those behaviour patterns, like shaking or killing bite, described 

 above. The inhibition of the two-year-old polecats to kill chicks is 

 secondary and probably due to social frustration. I got the impression that 

 the chicks became substitutes for a social companion. 



The different evaluation of the results of the experiments by Kuo, 

 Lehrmami, Riess and the author might first be due to the fact that the 

 former were interested only in the final outcome of the experiments. 

 They noted only: 'prey killed or not killed', 'retrieving or no retrieving', 

 'nest building or no nest building' but did not care very much about the 



