Rats are found throughout the United States. The most common rat found is the brown rat, also known as the common rat, sewer rat, or street rat. They are brown or gray in color, at adult age are usually around 11 inches in length, and weigh up to a pound and a half (at its largest). They have a long tail that can be as long as 24 inches. Rats are a part of the rodent group, which also includes squirrels, chipmunks, and guinea pigs. The brown rat has acute hearing and smell, but are known to have poor eyesight.
The brown rat is a nocturnal animal. They have been studied and have been found to communicate using ultrasonic vocalizations. To people, it may sound like a high pitch chirping. Females may produce up to 5 litters a year with the litters producing up to 14 young, with the average being 7. The gestation period is normally only 21 days. The life span of the brown rat is normally 2 years.