| Peromyscus difficilis attained its name not by behaving badly, but by proving hard to classify. Taxonomists, whose specialty is classification, try to figure out which species are most closely related to each other, and whether they are so closely related that they are, in fact, the same species. Living humans are all classified as Homo sapiens, but living deermice are divided into a great number of species, and scientists are still working to tease out evolutionary relationships in the genus Peromyscus.
Also known as:
Zacatecan Deer Mouse
Head and Body: 70-170 mm; Tail: 40-205 mm
15 to more than 110 g
Allen, J.A, 1891. Bulletin of the American Museum of Natural History, 3:298.
Mammal Species of the World (opens in a new window).
Mammalian Species, American Society of Mammalogists' species account (opens in a new window).