This is a collection of lists of mammal gestation period estimated by experts in their fields. The mammals included are only

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...

( marsupials and

placentals Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ...

) as some mammals, which are

monotremes Monotremes () are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals (Eutheria), and marsupials ( Metatheria). Monotremes are typified by structural differences in their br ...

(including

platypuses The platypus (''Ornithorhynchus anatinus''), sometimes referred to as the duck-billed platypus, is a semiaquatic, egg-laying mammal endemic to eastern Australia, including Tasmania. The platypus is the sole living representative or monotyp ...

and

echidnas Echidnas (), sometimes known as spiny anteaters, are quill-covered monotremes (egg-laying mammals) belonging to the family Tachyglossidae . The four extant species of echidnas and the platypus are the only living mammals that lay eggs and the ...

) lay their

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

. A marsupial has a short gestation period, typically shorter than placental. For more information on how these estimates were ascertained, see Wikipedia’s articles on

gestational age In obstetrics, gestational age is a measure of the age of a pregnancy which is taken from the beginning of the woman's last menstrual period (LMP), or the corresponding age of the gestation as estimated by a more accurate method if available. Su ...

. The gestation figures given here are shown in days. They represent average values and should only be considered as approximations.

Factors affecting the gestation period in mammals

There are several factors affecting the length of the gestation period in mammals.

Animal size/mass

There is a positive relationship between mass at birth and length of gestation in eutherian mammals. Larger mammals are more likely to produce a well-developed neonate than small mammals. Large mammals develop at an absolute slower rate compared to small mammals. Thus, the large mammal tend have longer gestation periods than small mammal as they tend to produce larger neonate. Large mammals require a longer period of time to attain any proportion of adult mass compared to small mammals.

The level of development at birth

More developed infants will typically require a longer gestation period.

Altricial In biology, altricial species are those in which the young are underdeveloped at the time of birth, but with the aid of their parents mature after birth. Precocial species are those in which the young are relatively mature and mobile from the mome ...

mammals needs less time to gestate compare to the

precocial In biology, altricial species are those in which the young are underdeveloped at the time of birth, but with the aid of their parents mature after birth. Precocial species are those in which the young are relatively mature and mobile from the mome ...

(well-developed neonate) mammal. A typical precocial mammal has a gestation period almost four times longer than a typical altricial mammal of the same body size. Precocial mammal species generally have greater adult body weights than altricial mammals as precocial mammals have markedly longer gestation periods than altricial mammals. The neonatal of larger mammals develop relatively more quickly and thus making it more likely that a large mammal would produce a more well-developed neonate as a consequence of its longer gestation period. In some cases, some mammal species may have similar gestation periods despite having significantly different body masses.

Environmental factor

In response to the conditions of the environment, some mammals, such as

bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most ...

delay the implantation due to the cold temperature in winter. Another factor is due to the shortage of food stocks during winter as the insects are being driven away and as the result, bat hibernate in pregnant condition. In

pinnipeds Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the walru ...

, the purpose of delayed implantation is in order to increase survival chance of the young animals as the mother ensure that the neonates are born at an optimal season. Scheffer, V. B., & York, A. E. (1997). Timing of implantation in the northern fur seal, Callorhinus ursinus. Journal of Mammalogy, 78(2), 675-683.

References

Citations

Sources

Gestation, Incubation, and Longevity of Selected Animals
*

David Crystal David Crystal, (born 6 July 1941) is a British linguist, academic, and prolific author best known for his works on linguistics and the English language. Family Crystal was born in Lisburn, Northern Ireland, on 6 July 1941 after his mother had ...

, '' The Cambridge Factfinder'' Cambridge:

Cambridge University Press Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by King Henry VIII in 1534, it is the oldest university press in the world. It is also the King's Printer. Cambridge University Pre ...

, 1998 (84).
Online animal encyclopedia

Study finds wide range in pregnancy length
{{DEFAULTSORT:Gestation Period Fertility Midwifery