THE BREEDING SEASON 25 



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. 1 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 vitality at 

 the approach of the breeding season. Moreover, many of the 

 secondary sexual characters, both those of the embellishing kind and 

 others as well, are developed during only a part of the year, which is 

 generally the period of breeding. 



A familiar example of this correspondence between the develop- 

 ment 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 (Cerints elaphus) 

 begins in September or October (see p. 44), 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. 2 

 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 known to drop his antlers as soon after the rutting season as 

 December, while, on the other hand, some immature animals in the 

 Lake District are said to carry them until May. After the shedding 

 of the antlers new ones begin to grow from the pedicles, the growth 

 taking place chiefly in July and August. When the new antlers 

 have reached their full development the " velvet " is shed (about the 

 beginning of September). The size of the antlers, and the number 

 of branches or " points," go on increasing every year throughout the 

 reproductive period of the stag's life and until he begins to decline 

 with old age. 3 



In the American prongbuck (Antilocapra americana), which is 

 unique among hollow-horned ruminants in shedding the horns every 

 year, the shedding follows the rutting season more closely than in 

 the stag. The rutting in this species begins in September, and lasts 

 about six weeks. In old bucks the horns are shed in October, while 



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



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

 to utter a loud bellowing noise. 



3 Cunningham (J. T.), Sexual Dimorphism, London, 1900. 



