About Peromyscus leucopus (Rafinesque, 1818)
Peromyscus leucopus adult body length, not including the tail, ranges from 90 to 100 mm (3.5 to 3.9 inches). The tail adds an additional 63 to 97 mm (2.5 to 3.8 inches) to total length. Young adult individuals weigh between 20 and 30 g (0.7 to 1.1 oz). The maximum lifespan for the species is 96 months. Mean life expectancy is 45.5 months for females and 47.5 months for males; in northern climates, average life expectancy ranges from 12 to 24 months. This species is similar in appearance to the closely related eastern deer mouse, Peromyscus maniculatus.
Urban populations of white-footed mice are densely concentrated in isolated urban parks, which creates conditions where sperm competition acts as an especially strong selective force. Genetic studies have detected signs of molecular-level evolution of reproductive traits in urban populations of this species. Compared to rural mice, genes linked to spermatogenesis, sperm locomotion, and sperm-egg interactions in urban mice show distinct regulatory patterns. As a result, intensified sperm competition in the dense mouse populations of urban areas has driven urban populations to evolve faster, more efficient sperm than rural populations possess.
