While wild populations are sometimes studied, Peromyscus species are also easy to breed and keep in captivity, although they are more energetic and difficult to handle than the relatively more tame M. musculus. For certain studies, They are also favored over the common laboratory mouse (M. musculus) and the laboratory rat (Rattus norvegicus). Apart from their importance in studying infectious diseases, Peromyscus species are useful for studying phylogeography, speciation, chromosomes, genetics, ecology, population genetics, and evolution in general. They are also useful for researching repetitive-movement disorders. Their use in aging research is because Peromyscus spp. , despite being of similar size to the standard laboratory mouse, have maximum lifespans of 5-7 years, compared to the 3-year maximum lifespan of ad libitum-fed laboratory strains or wild-caught M. musculus.