males that are iio( (o be used for breedino- sliould be 

 placed in separate pens. 



P>.nialei>-uiiiea pigs (sows) become sexually malui'e 

 ']() (o 45 days after birth and will bi'eed at tliis age. 

 Kstrus occurs eveiy 14 to 17 days and lasts about 

 '24- liours. 



The female comes into heat immediately after giv- 

 ing biith 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 five or more. A vigorous sow may produce 

 four o]- fi\e litters a year. Guinea pigs produce 

 young until they are 3 years old and may continue 

 until 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 

 ]-each this weight between 4 and () weeks of age. 



An adult male may weigh 1% to 21^ pounds. Un- 

 bred females are usually about 2 ounces lighter than 

 males at 18 months of ao-e. 



Long-haired guinea pig. 



