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The common species of pest rodents in New York are house mice, white-footed mice, deer mice, and Norway rats (roof rats are generally not found in NY). Adult mice and rats can be distinguished from each other by their size, some of their features, and fur patterns.

House Mouse

Adult mice are 2.5 to 3.75 inches long (63-95mm), with a tail that ranges from 2.75 to 4 inches in length. Compared to young/juvenile rats, they have large ears and eyes, and a pointier nose. Their body is uniformly colored, meaning that their backs and bellies are roughly the same greyish-brown. The tail is semi-naked and is as long as the body.

A mouse standing on crushed stone with twigs and leaf debris scattered about.
House mice can live outdoors if conditions are suitable, but can successfully live their entire life indoors.  Photo: NYSIPM. Click photos to see enlarged versions.

White-Footed Mouse and Deer Mouse

These two Peromyscus species with similar appearance and behaviors have two-tone fur with a darker back (grey or tan) and white belly. Because they are the same size as house mice, their coloring is a distinguishing feature.

a brown mouse with a pale belly on ground covered with dead leaves and twigs
This Peromyscus mouse was captured and tagged as part of a research project collecting information about ticks in NY.  Photo: NYSIPM.

Norway Rats

Adult Norway rats can reach 11 inches (28cm) in length, with a slightly shorter tail for a total length of 16 inches. A field identification test used in areas where roof and Norway rats coexist is to pull the tail toward the head. If the tail extends past the snout, it’s a roof rat; otherwise, a Norway rat. Like white-footed and deer mice, Norway rats tend to have two-tone fur, while the color may vary from brown to gray. These rats have small ears and eyes, and a blunt muzzle.

brown rat looking up at camera sitting on the ground strewn with pebbles and seeds
Norway rats are opportunistic feeders, and predictably, are found in areas such as parks where food is discarded. Photo: NYSIPM.

For rodents other than mice and rats, visit our Wildlife page.

A good resource for rodent identification is the CDC Rodents: Pictorial Key to Some Common United States Genera.