males (hat are not lo be used for breeding should be 

 ])la('ed in separate pens. 



Female guinea pigs (sows) become sexually mature 

 80 to 45 days after birth and will bieed at this age. 

 Estrus occurs e\ery 14 to IT days and lasts about 

 24 hours. 



The female comes into heat immediately after giv- 

 ing birth to a litter and usually mates within 10 to 12 

 hours. To insure regular mating, leave the breeder 

 males and females in the same cage. 



The gestation period of the guinea pig is 65 to 70 

 days. The average litter is three; some litters con- 

 tain hve or more. A vigorous sow may produce 

 four or fi\'e litters a year. Guinea pigs produce 

 young until they are 3 years old and may continue 

 initil they are 5. 



Growth 



Guinea pigs are vigorous and can care for them- 

 selves almost from birth. They are born fully haired, 

 with their eyes open, and with teeth. Within an hour 

 after birth, they begin running around. In 2 or 3 

 days they eat solid food. 



The young should be left with their mother for 3 

 to 4 weeks. 



Young guinea pigs gain weight rapidly and weigh 

 nearly half a pound in 30 days. Their growth is 

 slower for the next 18 months. 



Young guinea pigs weighing about one-half pound 

 are desired for many experimental purposes. They 

 reach this weight between 4 and 6 weeks of age. 



An adult male may weigh 1% to 2i/^ pounds. Un- 

 bred females are usually about 2 ounces lighter than 

 males at 18 months of age. 



Long-haired guinea pig. 



