Determinants of male reproductive success in American black bears

We determined annual male reproductive success in black bears (Ursus americanus) using DNA and field data from two populations in New Mexico. We identified the likely father for 78 of 120 genotyped cubs born during 1994–2000 and calculated reproductive success for 102 males known or presumed present within designated mating regions. Age was a strong determinant of reproductive success. The observed peak in reproductive success occurred at roughly the same intermediate age (10 years) as milder peaks in body size characteristics (11–12 years) and frequency of bear-inflicted wounds (13 years), suggesting body size and fighting might be important for mating. Success was negatively associated with the distance between home range centers of males and mothers. Success of young males (<7 years old) was also negatively associated with mature male (≥7 years old) density, and increasing density shifted the peak age of reproduction higher. The dispersed distribution of females likely limited the capacity of large mature males to dominate reproduction; therefore, success was determined by a complex set of variables.