Trade-offs between growth and reproduction in female bison.

The extent to which (a) larger females produce more or larger offspring, (b) reproduction imposes costs, and (c) the benefits of early reproduction outweigh the costs was examined for female bison (Bison bison) with data from an 8-year period. Description of ontogenetic patterns indicated that reproductive performance reached a plateau near the end of the growth period; changes with age in fecundity were little related to those of body weight during the typical reproductive lifespan (age 3-18 years). Examination of inter-and intra-individual variation showed that the relationship between growth and reproduction depends on the age of subjects.