The green frog (Rana clamitans) and northern leopard frog (R. pipiens) coexist at Van Pond in Emmet County, Michigan. To test the hypothesis that aggregating frogs benefit from increased vigilance, I slowly approached twenty 1 m2 plots staked out on the shoreline. I counted the number of frogs of both species in each plot (density) and measured the distance at which the first frog jumped (flight distance). Density was positively correlated with flight distance during three of eight trials conducted during a three-day period, suggesting that a potential predator may have been detected earlier by frogs when densities were higher. However, flight distances decreased significantly during the trials, suggesting that the frogs became habituated as the study progressed. A multiple linear regression indicated that both density and trial number were important in explaining the observed variation in flight distance. This study suggests that anuran amphibians may benefit from increased vigilance when aggregating, but further study is needed to confirm this hypothesis.