How do you sex a marmoset monkey?

To sex a marmoset monkey, you typically look at their external genitalia. Males have a more pronounced scrotum, while females have a vulva that is less noticeable and positioned closer to their body. Additionally, males may exhibit larger size and more robust body features compared to females. Observing behavior, particularly during mating season, can also provide clues, as males often display more territorial and aggressive behaviors.