Great Basin Naturalist


Data on reproduction of three species of pocket mice (Perognathus) occurring in northern Utah are summarized. Perognathus parvus and P. formosus bred in spring but not the remainder of the year. This occurred despite mild fall and winter temperatures and shallow snowcover. Litter sizes for P. parvus and P. formosus were similar to those reported by previous investigators. A small sample of P. longimembris indicated they may have much larger litters (averaging 5.78 young) than previously reported for laboratory populations. Adult body mass was positively correlated with testis mass in all species, and with litter size in P. parvus.