342 LIVE-STOCK RULES AND RECORDS 



Gestation and Incubation Figures 



The period of gestation is the time between the impregnation of 

 the ovum and the birth of the young. In egg-laying animals it is the 

 period of incubation. The length of this period is subject to con- 

 siderable variation, determined by various causes not well understood. 

 In general its length is in relation to the size of the animal. The 

 following list, and remarks, represents only a few animals and the 

 period of gestation of each (F. B. Mumford) : 



Elephant 20 to 30 months 



Giraffe 14 months 



Buffalo : 10 to 12 months 



Ass 12 months 



Mare 11 to 12 months 



Cow 9 to 9H months (285 days) 



Bear 6 months 



Sheep and goat 5 months (21 weeks) 



Sow 4 months 



Beaver 4 months 



Lion 3)^ months 



Dog, fox, or wolf 2 months 



Cat 50 days 



Rabbit 30 days 



Squirrel and rat 28 days 



The period of incubation extends as follows for domestic fowls: 



Turkey 26 to 30 days 



Guinea 25 to 26 days 



Pea hen 28 to 30 days 



Ducks 25 to 32 days 



Geese 27 to 33 days 



Hens 19 to 24 days (average 21) 



Pigeons 16 to 20 days 



Canary birds 13 to 14 days 



Small breeds hatch earlier. Hamburgs hatch at the end of the twen- 

 tieth day ; game bantams at the end of the nineteenth day. Duck 

 eggs hatch earlier under hens than under ducks, probably because of 

 the higher temperature of the hens' body. 



Small breeds of animals require rather less time than larger breeds, 

 although early maturity shortens the time. Cold weather retards the 

 process of incubation especially. According to Youatt, all animals vary 

 greatly without any known cause. The period of gestation in a horse 

 has been known to vary from ten to over twelve months. Tessier re- 

 ports 582 cases among mares, with a range of 287 to 419 days ; 1131 



