THE BREEDING SEASON 27 



The approach of the breeding season in many animals, if 

 not in most, is marked by a display of greater vitality, as mani- 

 fested by an increased activity, which relates not merely to the 

 sexual organs but to the whole metabohsm of the body. This 

 enhanced vitality is, as a rule, maintained throughout the 

 breeding season. Thus male birds at the time of pairing are 

 in a state of the most perfect development, and possess an 

 enormous store of superabundant energy. Under the influence 

 of sexual excitement they perform strange antics or rapid flights 

 which, as Wallace remarks, probably result as much from an 

 internal impulse to exertion as from any desire to please their 

 mates. Such, for example, are the rapid descent of the snipe, 

 the soaring and singing of the lark, the strange love-antics of 

 the albatross, and the dances of the cock-of-the-rock, and of 

 many other birds. ^ The migratory impulse, which, as already 

 mentioned, is closely associated with the periodic growth of the 

 sexual organs, may also very possibly be regarded as affording 

 evidence of increased vitahty at the approach of the breeding 

 season. Moreover, many of the secondary sexual characters, 

 both those of the embeEishing kind and others as well, are 

 developed during only a part of the year, which is almost 

 invariably the period of breeding. 



A familiar example of this correspondence between the 

 development of secondary sexual characters and the activity 

 of the reproductive organs is supplied by the growth of the 

 antlers in stags. At the time of rut, which in the red-deer 

 (Gervus elaphus) begins in September or October (see p. 48), 

 the antlers, or branched outgrowths from the frontal bones, are 

 completely developed, having shed their "velvet" or covering 

 of vascular skin. The animals during this season are in a state 

 of constant sexual excitement, and fight one another with their 

 antlers for the possession of the hinds. ^ By the end of the year 

 the fighting and excitement have ceased, and the stags begin 

 once more to herd together peaceably, and apart from the females. 

 Shortly afterwards the antlers are shed. In most parts of 

 Britain this occurs about April ; but a Highland stag has been 



' Wallace (A. R.), Darwinism, London, 1890. 



^ The larynx also is said to enlarge at this season, when the stag is wont 

 to utter a loud bellowing noise. 



