In my project, “Relationships between Blood Cell Types and Demographic/Morphological Factors in Rhesus Macaques,” I studied primarily white blood cell types, red blood cells, and platelets and how these cell types are correlated with measures such as age, sex, and pregnancy status in rhesus macaques. To do so, I analyzed blood samples collected from 456 animals over 4 years (2018 - 2021), as well as their associated demographic data, using R. These were free-ranging rhesus macaques on an island called Cayo Santiago, Puerto Rico. They are an especially excellent animal model due to their highly sociable nature. Sociability can greatly affect one’s health and their immune function, and we know that these blood cell types are greatly involved in immunity. Some interesting findings include a decline in lymphocytes as macaques age, but an increase in neutrophils. Furthermore, I found that lactating macaques had lower lymphocyte, monocyte, and red blood cell counts compared to non-lactating females. By analyzing measures of immunity via blood cell counts, relations between macaque characteristics and blood cell types can be inferred. This, in turn, can help us make more accurate predictions of blood cell ranges in the future, which can have implications in human medicine. Future analyses will incorporate behavioral data (such as grooming behaviors or aggression scores) and organ weights (specifically, spleen and liver, as they are involved in the immune response).