Male mutation bias theory explains that the observed mutation rate in males is often higher than in females because male gametes, sperm, undergo significantly more rounds of replication than female gametes, eggs (Miyata, et. al. 1987). Many studies support the existence of male-mutation bias, which can me measured as the ratio of the male to female mutation rates (α), but few have investigated the factors that might influence the magnitude of the bias. Both regional sequence variation and species-specific biology (e.g. generation time, sexual selection) can influence α. What is needed is a synthesis of previous studies. Here we develop a model to tease apart the relative influences of regional sequence variation and species-specific biology on the magnitude of male mutation bias. To do this have collected species-specific biological traits, accounted for differences in genome-wide regional variation across sequences from 34 mammalian species, computed α using nucleotide substitutions and developed a model to describe the relative influences of biological traits on the magnitude of male mutation bias.