SEXUAL BEHAVIOUR 8l 



recommended reviews for further reading are those by 

 Young2oo who deals especially with female mammals, 

 Bullough^^ who considers the case of the birds, and 

 Beach^i whose book is comprehensive. 



2. THE GONADS AND SEXUAL BEHAVIOUR 



When the anterior pituitary gland becomes active to 

 induce the growth of the gonads, this growth is ac- 

 companied by a steady increase in nervous tension. At 

 first this may result only in the development of ap- 

 parently confused and incomplete behaviour patterns 

 as when a bird excitedly visits its nesting hole for the 

 first time, but is then unable to do more than stand in 

 evident uncertainty as to what the next move should be. 

 Ultimately when the gonads are approaching full 

 maturity, and when environmental and psychological 

 conditions are satisfied, these behaviour patterns 

 crystallize into successful courtship activities, which 

 end in copulation and may be accompanied by such 

 other activities as nest-building. The compelling nature 

 of this increased activity is often referred to as the sexual 

 drive, and its strength is 'expressed in quantitative terms 

 that describe sexual activities with respect to frequency 

 of occurrence, vigour and persistence '.i®^ 



Increases in the sexual drive associated with in- 

 creased nervous tension are evident in a female rat on 

 the approach of oestrus. Only when the development 

 of the ovarian follicles is nearing completion will she 

 receive the male, and at this time she will actively seek 

 him, even if this involves crossing an electrically charged 

 grid which has been laid between them.^^^ The frequency 

 of her movements at this time are amazing, and can be 

 measured by keeping her in a revolving drum with a 

 counting mechanism attached. In this way it has been 

 shown that a rat which is not on heat may turn the drum 

 some one or two hundred times in a six-hour period, 

 but that during oestrus the same animal moves so 



