Although it is intuitively clear that an increase in antipredator behavior lowers an animal's risk of predation when predators are present, such benefits are not easily demonstrated. One study that did so found that well-fed guppies are more alert for predators and are consequently less likely to be killed than are their hungry counterparts, which feed with greater intensity. It is also well documented that a decrease in activity lowers an animal's risk of predation by reducing the probability of being detected or encountered by a predator. This effect was convincingly demonstrated by a study in which it was found that partially anesthetized tadpoles were less likely to be captured by dragonfly larvae than were unanesthetized tadpoles.