My DSRF-funded project addressed seasonal changes in hormones in the female-dominant blue-eyed black lemur. According to what’s called the Challenge Hypothesis, male mammals are expected to show increased androgen concentrations during the intensely competitive breeding season and lowered concentrations during periods of child-care, because androgens facilitate increased aggression while inhibiting affiliative behavior. Given that female lemurs have also been shown to face mating competition, there is reason to think that the Challenge Hypothesis may be applicable to them as well. To test this hypothesis, we assessed sex hormone fluctuations throughout the year in the aggressively female-dominant blue-eyed black lemur. In addressing this research question, I learned invaluable skills that I will hopefully apply to future projects: 1) Performing hormone assays on blood serum samples, and 2) using advanced statistical models, including general additive models to plot non-linear relationships, and linear mixed models to perform binary comparisons that control for non-independent samples. Ultimately, we observed that androgens increased for both sexes during the intensely competitive breeding season. Our previously-collected, albeit limited behavioral data also indicated that there was elevated female-to-male aggression during this same period. Our results may thus provide support for the Challenge Hypothesis in both sexes: Female androgens coincided with an increase in female aggression against males, perhaps as a means of exercising mate choice. Male androgens also increased, but we lack the behavioral data at this time to determine whether the increase was related to a competitive mating social situation. This experience of formulating and then answering a research question was incredibly fulfilling, and I am grateful for the opportunity to have a project to call my own.