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There is a positive relationship between mass at birth and length of gestation in eutherian mammals. [17] 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.
A litter is the live birth of multiple offspring at one time in animals from the same mother and usually from one set of parents, particularly from three to eight offspring. The word is most often used for the offspring of mammals , but can be used for any animal that gives birth to multiple young.
In the English language, many animals have different names depending on whether they are male, female, young, domesticated, or in groups. The best-known source of many English words used for collective groupings of animals is The Book of Saint Albans, an essay on hunting published in 1486 and attributed to Juliana Berners. [1]
Animals by year of birth. For humans by year of birth, see Category:Births by year This is a container category. Due to its scope, it ...
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]
Most mammals are viviparous, giving birth to live young. [1] However, the five species of monotreme, the platypuses and the echidnas, lay eggs. The monotremes have a sex determination system different from that of most other mammals. [2] In particular, the sex chromosomes of a platypus are more like those of a chicken than those of a therian ...
Mammals during pregnancy can have one or more gestations at the same time, for example in a multiple birth. [2] The time interval of a gestation is called the gestation period. In obstetrics, gestational age refers to the time since the onset of the last menses, which on average is fertilization age plus two weeks. [3]
The class Mammalia is divided into two subclasses based on reproductive techniques: egg-laying mammals (yinotherians or monotremes - see also Australosphenida), and mammals which give live birth . The latter subclass is divided into two infraclasses: pouched mammals ( metatherians or marsupials ), and placental mammals ( eutherians , for which ...