Reproductive tactics among deer mice of the genus Peromyscus

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Abstract
Life history tactics were assessed for 18 species and subspecies of deer mice with respect to nine growth and reproductive parameters. Four of the six tropical species investigated generally exhibited K-type tactics. The tropical Peromyscus yucatanicus has adopted a colonizing r-strategy probably in response to repeated habitat destruction by fire; whereas the large Peromyscus thomasi possesses both r- and K-type characteristics. With respect to most parameters, many temperate species represent a rather homogenous aggregate that is well differentiated from the tropical forms. One outlier, Peromyscus californicus, combines moderate body size and low fecundity with short gestation period and high relative birth mass. Peromyscus crinitus, an inhabitant of unproductive, rocky canyons, has evolved a late time to weaning and a very high relative birth mass. Temperate sylvan taxa have evolved larger litter sizes than pastoral taxa; this may allow them to respond to temporal changes in food availability. Most species possess characteristics that represent a compromise between the r and K extremes. Among the parameters examined those most highly correlated with one another are adult mass, age at eye opening, and relative biomass of offspring. Large mice have prolonged developmental times and smaller relative total neonatal biomass. The relationship between litter size and adult mass or latitude appears complex. In several cases, phylogenetically distant taxa have evolved similar reproductive habits, while in other situations closely related taxa have adopted divergent strategies.