How and when do rats give birth? - briefly
Rats gestate for approximately 21–23 days and can produce litters of six to twelve pups after reaching sexual maturity at about five to six weeks of age. Breeding occurs throughout the year, with females capable of conceiving shortly after giving birth.
How and when do rats give birth? - in detail
Rats reach sexual maturity between five and eight weeks of age, with females entering estrus cycles that last four to five days. Ovulation occurs spontaneously during the dark phase of the cycle, and receptive behavior appears within the first few hours of estrus. Mating typically takes place in the late evening, and a single copulatory event can result in fertilization.
Gestation lasts approximately twenty‑three days, ranging from twenty to twenty‑four days depending on strain and environmental conditions. Early pregnancy is marked by a slight increase in abdominal diameter and a subtle change in nipple coloration. By the third week, the abdomen enlarges noticeably, and the female exhibits nesting behavior, gathering material such as shredded paper or cloth.
Labor proceeds in three stages:
- First stage: Cervical dilation and uterine contractions begin, lasting 30–60 minutes. The female may emit vocalizations and display restlessness.
- Second stage: Delivery of pups occurs rapidly, with each offspring expelled at intervals of one to three minutes. Litters commonly comprise six to twelve pups, though numbers can vary from one to twenty.
- Third stage: Expulsion of the placenta follows each birth, and the mother licks the neonates to stimulate respiration and clear fluids.
Newborn rats are altricial: hairless, eyes closed, and completely dependent on maternal care. The mother provides thermoregulation, nutrition through milk, and protection for approximately three weeks, after which weaning begins. Throughout lactation, the female’s food intake increases markedly to support milk production.
Reproductive efficiency is high; a single female can produce up to seven litters per year under optimal conditions, resulting in exponential population growth when resources are abundant.