Gestation period

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For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth.[1] The duration of this period varies between species.

Duration[edit]

For most species, the amount a fetus grows before birth determines the length of the gestation period. Smaller species normally have a shorter gestation period than larger animals.[2] For example, a cat's gestation normally takes 58–65 days while an elephant's takes nearly 2 years (21 months).[3] However, growth does not necessarily determine the length of gestation for all species, especially for those with a breeding season. Species that use a breeding season usually give birth during a specific time of year when food is available.[2]

Various other factors can come into play in determining the duration of gestation. For humans, male fetuses normally gestate several days longer than females and multiple pregnancies gestate for a shorter period.[2] Ethnicity may also lengthen or shorten gestation.[4] In dogs there's a positive correlation between gestation time and a small litter size.[clarification needed][citation needed]

Gestational periods[edit]

Animal gestation calendar, 1917. Dates of service and date of birth for mares, cows, ewes, sow, and variation in gestation periods. Also gives gestation periods for ass, goat, dog, cat, rabbit, guinea pig, goose, turkey, duck, hen, guinea hen and pigeon.
Mammal Gestation period (days) Reference
Min Max Average
Alpaca 335 366 350 [5][6]
Baboon 187
Bear (black) 220 [7]
Bear (grizzly) 215
Bear (polar) 241
Beaver 122
American bison 217
Camel (Bactrian) 360 420 390
Cat (domestic) 58 67 64
Chimpanzee 230 250 240
Chinchilla 105 115 110 [8]
Chipmunk 31
Cow 279 292 286
Deer (white-tailed) 201
Dog (domestic) 58 65 61
Donkey 365
Walrus 456
Elephant (Asian) 617
Elephant (African) 645
Elk (wapiti) 240 250 245
European mink 38 76 57 [8]
Ferret (domestic) 41 42 41 [8]
Fox (red) 52
Gerbil 22 26 24 [8]
Giraffe 420 450 430
Goat (domestic) 145 155 150
Gorilla 255 260 257
Guinea pig 56 74 65 [8]
Hamster 16 23 20
Hippopotamus 225 250 237
Horse 330 342 336
Human 259 280 270
Kangaroo 42
Leopard 92 95 93
Lion 108
Llama 330
Mink 40 75 57
Monkey (rhesus) 164
Moose 240 250 245
Mouse (domestic white) 19
Mouse (meadow) 21
Muskrat 28 30 29
Opossum (Virginia) 12 13 12
Otter 60 86 73
Pig (domestic) 112 115 113
Porcupine 210
Puma 90
Rabbit (domestic) 28 35 31 [8]
Raccoon 63
Rat 21 23 22 [9]
Rhinoceros (black) 450
Seal 330
Sea lion (California) 350
Sheep (domestic) 144 151 147
Squirrel (gray) 30 40 35
Tiger 105 113 109
Whale (sperm) 480 590 535
Wolf 60 68 64
Wombat 26 28 27
Zebra (Grant's) 361 390 375

See also[edit]

References[edit]

Notes[edit]

  1. ^ "Gestation period". McGraw-Hill's AccessScience Encyclopedia of Science & Technology Online. McGraw-Hill. 
  2. ^ a b c "gestation". Britannica - The Online Encyclopedia. Encyclopædia Britannica. 
  3. ^ "Average Animal Gestation Periods and Incubation Times". MSN Encarta. Microsoft. Archived from the original on 2009-10-31. 
  4. ^ "Does gestation vary by ethnic group? A London-based study of over 122000 pregnancies with spontaneous of labour". International Journal of Epidemiology. 
  5. ^ Paris Hill Farm. "Alpacas 101". Retrieved 2012-07-14. 
  6. ^ Northwest Alpacas. "Alpaca Q&A". Retrieved 2012-07-14. 
  7. ^ University of Michigan. "Ursus Americanus". Retrieved 2013-01-16. 
  8. ^ a b c d e f Anamnese en lichamelijk onderzoek bij gezelschapsdieren, A.Rijnberk, F.J.van Sluis, 2nd print, Bohn Stafleu van Loghum, 2005, (Current Dutch veterinary examination study book for small domestic mammals)
  9. ^ The Laboratory Rat , 2nd Edition, Eds. Mark A. Sucklow, Steven H. Weisbroth, and Craig L. Franklin. Page 151.