ON THE BREEDING HABITS OF BUTLER'S GARTER- 

 SNAKE. 



ALEXANDER G. RUTHVEN, 

 MUSEUM OF NATURAL HISTORY, UNIVERSITY OF MICHIGAN. 



Relatively few observations have been made on the breeding 

 habits of snakes, at least few have been published, and there has 

 appeared in print considerable misinformation on the subject, 

 due principally to wrong identification of species. There is 

 especially a deplorable lack of careful studies of the life-histories of 

 the different forms. 1 Concerning the North American forms, 

 we know that some are ovo-viviparous and others oviparous, 

 that copulation probably takes place ordinarily in the spring, 

 although in one species it has been said to occur also in the fall, 2 

 that the young appear in the late summer, and there is some 

 evidence that there is a gregarious tendency in the breeding 

 season that may lead to the formation of "piles" of snakes. 3 

 But of the exact time of copulation, the courtship reactions, the 

 significance and commonness of the "snake piles," the length of 

 the gestation period in the different forms, and kindred subjects 

 only the most meager data have been gathered. 



During the present year the writer has been able to get a pair 

 of Butler's garter-snake (Thamnophis butleri Cope) to breed in 

 captivity and has carried the female over the period of gestation. 

 On April 9, which was about the first day in spring when the 

 snakes were at all active in this region, a male and female of this 

 species were found together near Ann Arbor. These failed to 

 copulate in captivity, although the male courted the female 

 assiduously for several days. On April 10, seven specimens were 

 collected, and a lot consisting of five males and a large female 



1 An excellent summary of the data on the breeding habits of certain North 

 American snakes is given by O. P. Hay, Proc. U. S. Nat. Mus., XV., pp. 385-398. 



2 Coues and Yarrow, Bull. Geol. and Geog. Surv. Terr., IV., 278. 



3 For a resume of the literature on this subject see Ruthven, A. G., Bull. U. S. 

 Nat. Mus., 61, pp. 13-14. 



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