Fig. 2 |. Example of foraging and escape choice, and the cost-of-fleeing and cost-of-staying curves.

a | The solitary prey (for example, a zebra) must make a decision about whether to flee to safety when a predator is approaching (for example, a lion). The flight initiation distance (FID) is the measurable distance at which the prey makes the decision to flee from an approaching threat². The FID is influenced by several factors, including the degree of threat posed by the predator (for example, whether it is a fast-moving or slow-moving predator) and the value of its current location (for example, there is an abundance of food or mates). b | The schematic represents the cost of fleeing versus remaining and is based on the model proposed by Ydenberg and Dill⁷⁶. As the distance between the prey and the predator decreases, the cost of fleeing decreases (red line), whereas the cost of not fleeing increases (blue line). d* represents the optimal distance between the prey and the predator at which the prey should flee. c | In situations in which there are multiple benefits of remaining at a particular patch but a single cost of fleeing, d* is longer for the higher of the two cost-of-not-fleeing curves. d | Conversely, d* is longer for the lower of the two cost-of-fleeing curves when there is a single cost-of-not-fleeing curve². d*_CH, high cost; d*_CL, low cost; d*_NH, not fleeing, high cost; d*_NL, not fleeing, low cost. Adapted with permission from REF.²,Cambridge University Press.