How do mice hatch? - briefly
Mice are placental mammals; their embryos develop inside the mother’s uterus and are born as live, hairless pups after a gestation of roughly three weeks.
How do mice hatch? - in detail
Mice are placental mammals; their offspring are born live after a gestation period of roughly 19‑21 days. Fertilization occurs in the oviduct, after which the zygote travels to the uterus and implants into the endometrial lining. The developing embryo forms a placenta that supplies oxygen, nutrients, and waste removal through the maternal blood supply.
Embryonic development proceeds through distinct stages:
- Cleavage and blastocyst formation (days 1‑4): rapid cell division produces a morula that becomes a blastocyst, which attaches to the uterine wall.
- Organogenesis (days 5‑15): the three germ layers differentiate into major organ systems; limb buds, neural tube, and heart begin to function.
- Fetal growth (days 16‑20): skeletal ossification, fur development, and lung maturation occur. By day 19, the fetus reaches a weight of about 0.5 g and is fully covered in hair.
Labor is initiated by hormonal signals, primarily a surge of oxytocin and prostaglandins, which contract the uterus. Each pup is enclosed in a thin amniotic sac that ruptures shortly before delivery. The mother assists by licking the newborns, stimulating respiration and removing the sac remnants. Litters typically comprise 5‑12 individuals, each born with closed eyes and underdeveloped sensory organs, which open within a few days.
Post‑natal care includes frequent nursing, thermoregulation through nest building, and rapid growth; pups double their birth weight within the first week. The entire process—from conception to independent weaning—occurs within a month, illustrating the efficient reproductive strategy of this species.