The most common rat in homes is the Brown rat, known by other names Norway rat, roof rat, wharf rat, etc. The females usually live 1 yr in the wild and can reproduce yr round, having 8-14 pups per litter with 3 females per litter. The females mature to reproduction maturity within 5 weeks and pregnancy is only 3 weeks long. This means that a rat infestation can increase by a power of 10 in just 4 months.
Don't allow a rodent infestation to linger, call a licensed pest operator right away