Vigilance within troops plays a key role in the survival of vervet monkeys (Chlorocebus pygerythrus) and the success of their offspring. We hypothesized that males would display more vigilant behavior than females and juveniles within troops, because troop males mate with many females and consequently achieve greater fitness by keeping the females safe so they can breed more often. Females, on the other hand, maximize their fitness by producing and caring for a single juvenile. Numerous troops of vervet monkeys were observed in multiple, moderately-forested areas within Wits Rural Facility near Acornhoek, South Africa. We categorized the monkeys based on their age and sex. Seven behaviors were recorded including vigilance, idleness, grooming, playing, sleeping, foraging, and roaming. Males displayed more vigilant behavior (50%), than females (27.8%) and juveniles (9.4 %). All data were found to be significant; males vs. females (p=0.004), males vs. juveniles (p < 0.001), females vs. juveniles (p < 0.001). These data support our hypothesis that male vervet monkeys display the most vigilant behavior within a troop, which suggests that males are the guardians of their troops.