Female rats may potentially give birth to over 200 babies per year, depending on the litter size. However, there are many factors that influence the annual total, such as the type of rat, the environment, and the health of the female.
How Many Baby Rats Per Litter?
Different types of rats may also give birth to a varying number of babies. The two main species of rats include Norway Rats and Roof Rats. The roof rats prefer the warmer climates and are often found along the coastal regions of the US. Norway rats are found just about everywhere else. A third species of rat, the Woodrat, can be found in the desert Southwest but is not considered for this article.
Healthy female Norway rats, when they reach sexual maturity, may birth up to 15 or 16 babies in a single litter, in optimal conditions. However, they often only give birth to the number of babies that they can naturally nurture. As a female rat has 12 nipples, 12 is often the upper limit.
While 12 is considered a large litter and 15 or 16 babies is possible, the average number is 8 to 10 babies per litter of Norway rats.
Roof rats and Norway rats are closely related. However, the roof rats do not always produce as much offspring.
The average female roof rat gives birth to five to eight babies per litter. They also have fewer teats. While a female Norway rat has 12 nipples, a roof rat has 10.
How Many Litters Do Rats Have Each Year?
Female rats can get pregnant shortly after birth. The gestation period for most rats is about three weeks. A healthy female may give birth to a litter every three to four weeks. However, female rats rarely get pregnant this frequently.
While it is possible for rats to have 13 to 17 litters each year, the average female Norway rat has 4 to 6 litters. The typical roof rat has three to four litters per year.
The number of rats born does not equal the number of rats that survive to maturity. Both Norway and roof rats mature in about three months.
A healthy female Norway rat may birth between 30 and 60 rats in a year. However, they typically only successfully wean 20 rats annually.
How Many Babies Do Pet Rats Have?
Pet rats do not usually have as many babies as wild rats. In the wild, rats are free to breed frequently. In captivity, pet rats are often separated to help avoid pregnancy.
Domesticated animals of all types, including rats, often produce fewer babies per litter and fewer litter compared to their wild counterparts. Rats adapt to domestication, becoming more passive. The presence of humans also makes them less likely to breed as
frequently.
These changes impact their breeding and behavior. They are less territorial and less likely to establish the same roles within their nest compared to wild rats.
In the end, the number of babies that a rat may have can vary. Norway rats are bigger and often have more babies. While roof rats may average 5 to 8 babies per litter, Norway rats may give birth to 8 to 10 babies. They also have more litters per year, getting pregnant up to
six times instead of up to four times.
