The flush early and avoid the rush hypothesis holds after accounting for spontaneous behavior

When approached by a predator, prey make economic decisions between remaining where they are and obtaining benefits from their current activity or leaving and enhancing their safety. The "flush early and avoid the rush" hypothesis suggests that animals that flee to escape approaching threats flee soon after they become alert to an approaching predator so as to reduce any costs incurred by ongoing monitoring of the predator. This hypothesis has been supported by several studies, but some researchers argue the relationship may be partially or entirely a consequence of bouts of spontaneous vigilance and/or bouts of spontaneous locomotion (vigilance or locomotion that occur when the animal is unaffected by a predator), rather than an economic decision related to the approaching predator. If this were true, spontaneous vigilance might incorrectly be recorded as alert distance (predator–prey distance when the prey becomes aware of and begins to monitor the predator) and spontaneous locomotion might be incorrectly recorded as flight initiation distance (predator–prey distance when escape begins). To evaluate these potential effects, we recorded the intervals between bouts of spontaneous vigilance and locomotion by yellow-bellied marmots (Marmota flaviventris). We used these baseline rates to conduct a series of alert distance–flight initiation distance regressions after removing potentially spurious observations recorded as alert distance or flight initiation distance. Although spontaneous vigilance and spontaneous locomotion may lead to artifactual increases in flight initiation distance as alert distance increases, the fundamental relationship remains after effects of spontaneous movements have been removed, supporting the flush early and avoid the rush hypothesis. We tested a key challenge of the "flush early and avoid the rush" (FEAR) hypothesis; our results provide strong support for the hypothesis.