Old habits die hard: pigeons maintain route fidelity but reduce flight altitude when exposed to a raptor-like robot

Prey organisms employ a range of adaptive strategies to mitigate predation risk, including camouflage, active predator deterrence by collective anti-predator behaviours, specialized predator evasion tactics, and spatial or temporal avoidance of predators. The latter may involve memorizing locations of non-lethal predator encounters and altering movement routines to subsequently avoid areas where such encounters are more likely, in line with the so-called ‘landscape of fear’ concept. We investigated whether and how experienced homing pigeons (Columba livia) altered their homing behaviour upon repeated exposures to simulated attacks by a robot mimicking a peregrine falcon (RobotFalcon), a common aerial predator of pigeons, along their consolidated homing route. Pigeons showed evidence of immediate responses to predator detection, considerably reducing their flight altitude (by ~ 50%) when they approach the RobotFalcon, starting when ~ 200 m from it, and maintained such lower altitude also when leaving the RobotFalcon area. Yet, pigeons showed no evidence of altering their path to avoid the area where they were more likely to encounter the RobotFalcon, even in subsequent flights when the RobotFalcon was absent, indicating that the tendency to retrace consolidated routes was not affected by predation risk. Our experiment showed that pigeons adaptively responded to immediate predation risk by flying closer to the ground, which may reduce the success of aerial predator attacks. These findings challenge the landscape of fear paradigm, suggesting that maximising energetic efficiency and flying over well25 known landscapes, which may make immediate predator responses more effective, are prioritized over minimizing predation risk by flying across novel and unknown environments