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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. [18] Large mammals require a longer period of time to attain any proportion of adult mass compared to small mammals. [19]
The duration of this period varies between species. 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 ...
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]
Gestation, called pregnancy in humans, is the period of time during which the fetus develops, dividing via mitosis inside the female. During this time, the fetus receives all of its nutrition and oxygenated blood from the female, filtered through the placenta, which is attached to the fetus' abdomen via an umbilical cord.
The mean pregnancy length has been estimated to be 283.4 days of gestational age as timed from the first day of the last menstrual period and 280.6 days when retrospectively estimated by obstetric ultrasound measurement of the fetal biparietal diameter (BPD) in the second trimester. [12]
A mare may be in heat for 4 to 10 days, followed by approximately 14 days in diestrus. Thus, a cycle may be short, totaling approximately 3 weeks. [21] Horses mate in spring and summer; autumn is a transition time, and anestrus occurs during winter.
Wild horse Temporal range: earliest Middle Pleistocene -Recent 0.8–0 Ma Pre๊ ๊ O S D C P T J K Pg N ↓ Top left: Equus ferus caballus (horses) Top right: Equus ferus przewalskii (Przewalski's horse) Below left: Equus ferus ferus † (tarpan) Below right: Equus ferus fossil from 9100 BC Conservation status Endangered (IUCN 3.1) Scientific classification Domain: Eukaryota Kingdom ...
The gestation period lasts for about eleven months, or about 340 days (normal average range 320–370 days). During the early days of pregnancy, the conceptus is mobile, moving about in the uterus until about day 16 when "fixation" occurs.