RELATION OF MAMMALS TO FISHES 1 2/ 



victims. Many well-known species of snakes habitually eat mice, and 

 the bull snake is often called the gopher snake, because of its fondness 

 for gophers. The rodent-eating snakes doubtless do some good in this 

 way, but their digestion is slow, they require little food and often go 

 for long periods without food, so the total number of rodents eaten 

 by one snake in a year is probably not large. 30 However, experiments 

 with captive snakes indicate that a bull snake would be able to con- 

 sume one pocket gopher a month. In Kansas it was estimated that a 

 moderate infestation of an alfalfa field would be about eight gophers 

 an acre. Consequently one snake would be able to keep an acre of 

 groun(J free from gophers. 31 As mice are much smaller, the snakes 

 could of course consume a much larger number of them. The senior 

 author of this book once found three full-grown field mice in one small 

 gartersnake. One bull snake contained thirty-five mice, 32 mostly young, 

 and another contained four full-grown gophers. 33 Many young musk- 

 rats are eaten by snakes. 34 Snakes eat their prey by swallowing the crea- 

 tures whole, instead of biting off pieces and chewing them. They will 

 take almost any animal not too large to be swallowed, which, in case of 

 a boa constrictor or python, means a rather large animal. 



Morse has described the way a bull snake captures a gopher. 35 The 

 rattlesnake is listed as one of the enemies of ground squirrels 36 and 

 one contained a wood rat. 37 A python attacked a spaniel, 38 another 

 swallowed a 7O-pound buck, 39 and a cobra killed a tiger. 40 Poisonous 

 snakes are well known as a menace to human beings as well as to 

 other mammals. In British India in 1910 there were 22,478 deaths of 

 human beings and in 1909 there were 21,364 because of snake bites. 41 

 In 1895 on ly T ^46 persons were reported killed by venomous snakes 42 

 but statistics were much less complete then than now. 



Alligators and crocodiles will kill almost any small mammal up to 



30 Burnett, Office Colorado State Entom. Circular No. 18, 1916. 



31 Hisaw and Gloyd, The bull snake as a natural enemy of injurious rodents, Journ. 

 Mammalogy, vn, 200-205, 1926. 



32 Pack, Copeia, No. 68, p. 16, 1918. 



33 Ruthling, Copeia, No. 37, p. 91, 1916. 



34 Arthur, Louisiana Dept. Conservation, Bull. No. 18, p. 269, 1928. 



85 Morse, The way of a snake with a gopher, Copeia, No. 164, pp. 71-72, 1927. 



36 Merriam, U. S. Biol. Surv. Circular No. 76, p. 7, 1910. 



37 Mearns, U. S. Natl. Museum Bull. No. 56, p. 479, 1907. 



38 Smith, Python attacking a spaniel, Journ. Bombay Nat. Hist. Soc., xxx, 485, 

 1925 ; Journ. Mammalogy, vui, 325, 1927. 



39 Holland, Pythons and their prey, The Field (London), CL, 395, 1927; Journ. 

 Mammalogy, ix, 81, 1928. 



40 Spence, Sanderson and Prater, Tiger killed by a cobra, Journ. Bombay Nat. Hist. 

 Soc., xxx, 705, 1925. 



"Science, xxxvii, 938, 1913. 



42 Amer. Naturalist, xxxi, 77-78, 1897. 



