Developing an integrative understanding of escape mode decisions

Optimal escape theory predicts that individuals should escape when the costs of staying (risk of being injured or killed) exceed the costs of leaving (energetic costs of escape, lost foraging opportunities and costs incurred for monitoring the approaching predator). We extend these theoretical principles to analyse preferences for alternative escape modes in a model animal group, birds, which can escape by either flight (costlier but safer) or using cheaper but riskier alternatives (jump, walk, or swim). We used a large, published database that included 21 222 records on 179 species taken in 15 European localities during the breeding seasons of 2009–2019, with data on escape mode, latitude, habitat (urban or rural), precipitation and temperature. Most individuals escaped by taking flight (15 940 records; 79%). Variation in escape mode decisions was mostly driven by species-specific traits (body size, diet), whereas external environmental variables (climate, geography, habitat) showed small effects. Flight initiation distances were longer when birds escaped by taking flight than when they chose lower-cost alternatives. Overall, escape mode preferences showed spatial and temporal variation compatible with expectations from risk–energy trade-off optimization. Escape mode decisions seemed more related to predation avoidance and flight initiation distance decisions to energy-saving goals. Thus, escape mode preferences interacted with fleeing–staying decisions, suggesting a behavioural integration of different aspects of escape strategies under a general optimization model. • Optimal escape distance occurs when costs of staying exceed costs of leaving. • Escape by flight or by less costly but riskier modes should modulate escape distance. • Escape mode preferences indicated a risk-energy trade-off optimization in birds. • Mode and distance decisions were integrated under a general optimization model. • Mode was more related to predation avoidance and distance to energy-saving.