Movement and direction of movement of a simulated prey affect the success rate in barn owlTyto albaattack

116.The present study was aimed at testing a novel idea, that rather than maximizing theirdistance from a predator during close-distance encounters, prey species are better offmoving directly or diagonally toward the predator in order to increase the relative speedand confine the attack to a single available clashing point. We used two tamed barnowls Tyto alba to measure the rate of attack success in relation to the direction of preymovement. A dead mouse or chick was used to simulate the prey, pulled to variousdirections by means of a transparent string during the owl’s attack. Both owls showed ahigh success rate in catching stationary compared with moving food items (90% and21%, respectively). Success was higher when the prey moved directly away, rather thantowards the owls (50% and 18%, respectively). Strikingly, these owls had 0% success incatching food items that were pulled sideways. This failure to catch prey that movesideways may reflect constraints in postural head movements in aerial raptors thatcannot move the eyes but rather move the entire head in tracking prey. So far there isno evidence that defensive behavior in terrestrial prey species takes advantage of theabove escape directions to lower rates of predator success. However, birds seem toadjust their defensive tactics in the vertical domain by taking-off at a steep angle, thusmoving diagonally toward the direction of an approaching aerial predator. Thesepreliminary findings warrant further studies in barn owls and other predators, in bothfield and laboratory settings, to uncover fine predator head movements during hunting,the corresponding defensive behavior of the prey, and the adaptive significance of thesebehaviors.D. Eilam (correspondence) and E. Shifferman, Department of Zoology, Tel-AvivUniversity, Ramat-Aviv 69 978, Israel. E-mail: eilam@post.tau.ac.il