Escape behaviour varies with distance from safe refuge

Abstract

Locomotor performance and behaviour are important for escape from predators, yet the intersection of these strategies is poorly studied. Escape behaviour is context dependent, and optimal escape theory predicts that animals that are farther from a safe refuge will generally use faster running speeds but might choose to use more variable escape paths. We studied locomotor performance and behaviour of six-lined racerunner lizards (Aspidoscelis sexlineata) escaping on natural surface runways that were varied experimentally to be either 5 or 10 m from a safe refuge. On the 5 m runway, lizards usually escaped directly towards the refuge, attained a slower maximal running speed (3.2 m s−1) at ~3 m from the start, and reached the target refuge in most of the trials (80%). On the 10 m runway, lizards used more variable behaviour, including reversals and turns, attained a faster maximal running speed (3.7 m s−1) at ~6 m from the start, and reached the final refuge in only 43% of trials. Free-ranging racerunners were rarely > 5 m from their nearest refuge and used escape paths that were typically < 5 m. Our findings align with predictions from optimal escape theory, in that the perceived risk of a predator–prey encounter can drive adjustments in locomotor behaviour and performance. Additionally, we show that the escape behaviour of free-ranging lizards closely matches their escape behaviour and performance during controlled escape trials.

Stop, then go! Rapid acceleration offsets the costs of intermittent locomotion when turning in Florida scrub lizards

“…Pausing may give the lizard time to locate the predator (in this case the human pursuer) while also stabilizing its field of view and alleviating motion blur (Kramer & McLaughlin, 2001; Trouilloud et al, 2004). In addition to offsetting the effects of motion blur, intermittent locomotion while evading a predator may also aid in finding alternate routes of escape (McElroy & McBrayer, 2021; Stojan‐Dolar & Heymann, 2010). The placement of pauses was not affected by the turn angle.…”

“…Intermittent locomotion (also referred to as stop-go running, pause-travel locomotion, and saltatory search) is defined as stopping for extended periods of time (usually only a few seconds) during bouts of running (Kramer & McLaughlin, 2001). This type of locomotion has been documented in many animals from various fishes (Kemp et al, 2009;Wilson et al, 2010) to terrestrial and arboreal mammals (McAdam & Kramer, 1998;Stojan-Dolar & Heymann, 2010;Vasquez, 2002) and reptiles (Higham et al, 2010;McElroy & McBrayer, 2021;Weinstein & Full, 2000). Several studies have quantified the benefits of intermittent locomotion.…”

“…The presence of obstacles, such as vegetation, woody debris, or rocks, requires turning, enhanced maneuverability, or alternative locomotor behavior (Brownsmith, 1977; Wynn et al, 2015). Animals may choose to alter their posture (bipedal running) to increase visual field use reactive feedback control to avoid obstacles (Fabian et al, 2022), or use intermittent locomotion to navigate obstacles (McElroy & McBrayer, 2021). Intermittent locomotion (also referred to as stop–go running, pause‐travel locomotion, and saltatory search) is defined as stopping for extended periods of time (usually only a few seconds) during bouts of running (Kramer & McLaughlin, 2001).…”

“…Because many animals visually identify movement to locate potential prey, deciding to become cryptic during locomotion may confuse a predator and cause it to lose sight (Herzog & Burghardt, 1974). In addition to aiding an animal in predator location and avoiding detection, the brief visual stabilization from intermittent locomotion (Avery, 1993; Probst et al, 1986) may also give prey a moment to identify nearby refuges and/or to decide on alternative escape routes (McElroy & McBrayer, 2021; Stojan‐Dolar & Heymann, 2010; Zamora‐Camacho, 2020).…”

“…While there are numerous studies exploring speed and intermittent locomotion on straight paths (McAdam & Kramer, 1998; Vasquez, 2002; Weinstein & Full, 2000), the use of intermittent locomotion when negotiating a turn is not very well understood. Many studies have documented that animals will run at near maximal speed straight to a known refuge (Kramer & Bonenfant, 1997; McElroy & McBrayer, 2021). Comparatively, little is known about the behavior and performance when turning during predator evasion.…”