8 INHERITANCE IN GUINEA-PIGS. 



HYBRIDIZATION EXPERIMENTS WITH CAVIA CUTLERI. 



LIFE HISTORY OF CAVIA CUTLERI. 



The primary object of my journey to Peru was to secure representa- 

 tives of the wild species of cavy, Cavia cutleri Bennett, known to exist 

 there. Four pairs of these animals captured at Arequipa were suc- 

 cessfully installed in cages at the Bussey Institution in January 1913. 



One of the males soon died without leaving descendants; the other 

 7 animals (4 females and 3 males) produced offspring in captivity, which 

 have continued to breed succesfully, though the stock has at times 

 been seriously reduced by disease in cold weather. Three generations 

 of descendants have been reared from the original stock of 7 animals. 

 Together they number 100 individuals, of which 47 are males and 53 

 females. All are very uniform in color, size, general appearance, and 

 behavior. 



Their color is a dull leaden gray-brown, well adapted to escape notice 

 amid the arid surroundings of their native habitat. The fur is agouti- 

 ticked and the belly light, but the yellow of the ticking and belly is so 

 pale as to resemble a dirty white or very light cream shade. The color 

 is much paler than that of the Brazilian species, Cavia rufescens } studied 

 by Detlefsen. The fur is also finer and softer, in which respect it 

 resembles the guinea-pig. The size of C. cutleri is about the same as 

 that of C. rufescens, and between one-third and one-half that of the 

 guinea-pig. The maximum weight of an adult male is about 525 grams ; 

 that of a domesticated male guinea-pig obtained in Arequipa (cfl002) 

 is nearly three times this amount. 



In wildness Cavia cutleri is very much like C. rufescens. The animals 

 live contentedly in small cages, 2 feet 6 inches square, but invariably 

 retreat under their box or conceal themselves in the hay if anyone 

 approaches. 



The extreme savageness toward each other of individuals of Cavia 

 cutleri makes it difficult to rear large numbers of them in captivity. It 

 is seldom possible to keep more than a single pair in a cage together 

 for any length of time. Two adult males will not live together peace- 

 ably under any circumstances, and if two females are placed together 

 in a cage with one male persecution of one female by the other usually 

 follows. Even when the young are allowed to grow up in the same 

 cage with their parents, family dissensions are likely to arise as soon as 

 the young become mature. 



The period of gestation (minimum interval between litters) averages 3 

 or 4 days shorter than in guinea-pigs, being 60 to 70 days, and the number 

 of young to a litter varies from 1 to 4. Fifty-three litters born in captivity 

 include exactly 100 young, an average of 1.89 young to a litter. The 

 size of litter occurring most frequently is 2, which has been recorded 



