Since the appearance of the second edition of Sydney A. Asdell's widely used Patterns of Mammalian Reproduction in 1964, the field of reproductive physiology has expanded dramatically. Accordingly, this revision adopts a different structure from previous editions, substituting empirical delineations for physiological interpretations. With the emphases now on a presentation of the published facts of mammalian reproduction, it provides a thorough compilation of what is known about the basic reproductive biology of each of the 4300 mammalian species.

To gather information, the authors examined more than 20,000 publications, dating up to 1992. They used primary sources as much as possible, supplementing them with English translations of Russian, Finnish, Chinese, and Japanese journals. The data are presented in taxonomic order. Each familial account summarizes the pattern of reproduction for the family and provides lists of citations arranged by topic of the literature on the endocrinology, reproductive anatomy, and reproductive physiology of the family. Following each account is a tabular listing of species-specific data for neonatal mass and size, weaning mass and size, litter size, age at sexual maturity, estrous cycle length, gestation length, lactation length, number of litters per year, and seasonality of reproduction. For each of these reproductive variables, the range of data gleaned from the literature is given, together with the source of each value listed.