Apex predators in terrestrial ecosystems, such as leopards in the African savanna, feed on a wide variety of prey species, yet it is unknown whether individuals specialize on certain prey, and whether specialization changes with body traits. Here, we asked whether individual specialization of adult leopards (Panthera pardus) varies with sex, body mass, body length and age classes. We used the variation of stable carbon and nitrogen isotope ratios in 643 segments of whiskers as a temporal record of past diets and established isotopic dietary niches for 36 adult leopards (18 males, 18 females). Based on a variance analysis for stable carbon isotope ratios, we found that between-individual variation was larger than within-individual variation, indicating a high degree of overall specialization within the studied leopards. Female adult leopards exhibited larger isotopic dietary niche widths than male adult leopards. Isotopic niche width did not vary with body mass, body length or age. Our data suggest a difference in the level of specialization between the sexes, which might be explained by more opportunistic feeding of small-sized female leopards, most likely connected with a higher use of small prey species of different isotopic composition. Inter-sexual resource partitioning likely facilitates territory sharing between the sexes.