Peromyscus gossypinus is one of the largest members of the genus Peromyscus in the US, and can be recognized by its dark color. The dorsal pelage of this species consists of two different types of hair: short, dark brown hair that covers the majority of the body, and longer, darker hair that covers the middle of the dorsum. The hair on the feet and ventral side is white. The tail is sparsely haired and relatively short, compared to other rodents.
The top of the skull is flattened and there is little or no postorbital process. The dental formula is 1/1, 0/0, 0/0, 3/3.
These mice measure 142 to 206 mm in length, of which 55 to 97 mm is the tail. They can weigh between 17 and 46 g.
Range mass: 17 to 46 g.
Range length: 142 to 206 mm.
Other Physical Features: endothermic ; heterothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike