Red deer individual landscapes of fear in response to human recreation

Abstract Animals adjust behavior to changes in perceived predation risk, even when risk is non-consumptive, as is the case for human recreation. However, individuals within populations can differ greatly in their plasticity towards perceived risk, especially when antipredator responses incur fitness costs via lost foraging opportunities. Therefore, risk-benefit trade-offs are usually made at the individual level. We test whether red deer (Cervus elaphus) inhabiting the Bavarian Forest National Park show individual variation in behavioral plasticity towards human disturbance. We measured human disturbance as the number of recreationists on the closest trail on a given day and used random regression to dissolve movement responses, measured as hourly step-length, of 63 GPS-collared red deer females to fine scale spatio-temporal variation in disturbance. We quantified behavioral state-specific between-individual variation along the disturbance gradient. At the population level, red deer responded to recreational disturbance during the middle of the day only, and reduced movement in response to recreation. However, population patterns masked strong between-individual variation in plasticity to recreational disturbance during the morning, midday, and evening, such that some deer reacted with increased or decreased movement rates while others responded little. Behavioral responses were mediated by vegetation cover with stronger responses in more open habitat. Flight responses are costly due to lost foraging opportunities. A shift in risk-benefit trade-offs when risk is non-lethal, as is the case for recreation in many national parks, may favor more human-tolerant individuals over time.