Animal escapology II: escape trajectory case studies

SUMMARYWe placed locusts in a wind tunnel using a loose tether design that allowed for motion in all three rotational degrees of freedom during presentation of a computer-generated looming disc. High-speed video allowed us to extract wing kinematics, abdomen position and 3-dimensional body orientation. Concurrent electromyographic (EMG) recordings monitored bilateral activity from the first basalar depressor muscles (m97) of the forewings, which are implicated in flight steering. Behavioural responses to a looming disc included cessation of flight (wings folded over the body), glides and active steering during sustained flight in addition to a decrease and increase in wingbeat frequency prior to and during, respectively, an evasive turn. Active steering involved shifts in bilateral m97 timing, wing asymmetries and whole-body rotations in the yaw (ψ), pitch (χ) and roll (η) planes. Changes in abdomen position and hindwing asymmetries occurred after turns were initiated. Forewing asymmetry and changes in η were most highly correlated with m97 spike latency. Correlations also increased as the disc approached, peaking prior to collision. On the inside of a turn, m97 spikes occurred earlier relative to forewing stroke reversal and bilateral timing corresponded to forewing asymmetry as well as changes in whole-body rotation. Double spikes in each m97 occurred most frequently at or immediately prior to the time the locusts turned, suggesting a behavioural significance. These data provide information on mechanisms underlying 3-dimensional flight manoeuvres and will be used to drive a closed loop flight simulator to study responses of motion-sensitive visual neurons during production of realistic behaviours. Supplementary material available online at

Section: Discussionmentioning

confidence: 99%

Bilateral flight muscle activity predicts wing kinematics and 3-dimensional body orientation of locusts responding to looming objects

McMillan

Loessin

Gray

2013

“…Away and towards responses are escapes with a rotation directed away from and towards the stimulus, respectively. A towards response does not necessarily imply that the final escape trajectory will be towards the stimulus, because an animal initially oriented at 170deg that makes a 20deg rotation towards the stimulus will end up having an escape trajectory of 150deg from the stimulus itself (Domenici et al, 2011). We note that, in contrast to the general convention adopted in this paper, some authors have based their definition of away and towards responses on the final trajectory (e.g.…”

Section: The Meaning Of Directionalitymentioning

confidence: 92%

“…whether prey escape by rotating their body away from or towards the threat. A theoretical framework for predicting escape trajectories is then presented, followed by a discussion of the emerging trends of escape trajectories in various animal taxa that is based on a survey of ET data from the literature in the accompanying paper (Domenici et al, 2011). We also consider taxon-specific physiology and ecology, the implications for the sensory and locomotor systems, the issue of context dependency and conclude with the significance of escape trajectories in terms of survival.…”

Section: Introductionmentioning

confidence: 99%

“…The term ET is used throughout to refer to escape trajectories in general, unless the particular way an ET has been measured needs to be noted. In these cases, the metrics ET 0 , ETЈ and ETЉ, briefly defined below, are used (Domenici et al, 2011). ET 0 spans 360deg based on whether, at the end of the escape, the threat remains on the side of the original stimulation (0-180deg) or not (180-360deg); ETЈ spans 360deg, with the sectors 0-180deg and 180-360deg corresponding to escapes directed to the right and left of the line directly away from the threat, respectively; ETЉ spans only 180deg from the threat, regardless of the side stimulated.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Animal escapology I: theoretical issues and emerging trends in escape trajectories

Domenici¹,

Blagburn

Bacon

2011

Self Cite

180

169

SummaryEscape responses are used by many animal species as their main defence against predator attacks. Escape success is determined by a number of variables; important are the directionality (the percentage of responses directed away from the threat) and the escape trajectories (ETs) measured relative to the threat. Although logic would suggest that animals should always turn away from a predator, work on various species shows that these away responses occur only approximately 50-90% of the time. A small proportion of towards responses may introduce some unpredictability and may be an adaptive feature of the escape system. Similar issues apply to ETs. Theoretically, an optimal ET can be modelled on the geometry of predator-prey encounters. However, unpredictability (and hence high variability) in trajectories may be necessary for preventing predators from learning a simple escape pattern. This review discusses the emerging trends in escape trajectories, as well as the modulating key factors, such as the surroundings and body design. The main ET patterns identified are: (1) high ET variability within a limited angular sector (mainly 90-180deg away from the threat; this variability is in some cases based on multiple peaks of ETs), (2) ETs that allow sensory tracking of the threat and (3) ETs towards a shelter. These characteristic features are observed across various taxa and, therefore, their expression may be mainly related to taxon-independent animal design features and to the environmental context in which prey live -for example whether the immediate surroundings of the prey provide potential refuges.

“…Most prior research on optimal evasive responses by birds has focused on locomotion rather than sensory inputs (Hedenstrom and Rosen, 2001;Howland, 1974;Van den Hout et al, 2010;Weihs and Webb, 1984). A recent review of prey escape strategies has commented on the tendency of prey to double back and move toward the pursuing predator (Domenici et al, 2011), a strategy found to result in lower capture rates for owls (Shifferman and Eilam, 2004). Such prey maneuvers may be attempts to move out of the predator's high acuity visual field.…”

Section: Research Articlementioning

confidence: 99%

Falcons pursue prey using visual motion cues: new perspectives from animal-borne cameras

Kane

Zamani

2014

117

107

This study reports on experiments on falcons wearing miniature videocameras mounted on their backs or heads while pursuing flying prey. Videos of hunts by a gyrfalcon (Falco rusticolus), gyrfalcon (F. rusticolus)/Saker falcon (F. cherrug) hybrids and peregrine falcons (F. peregrinus) were analyzed to determine apparent prey positions on their visual fields during pursuits. These video data were then interpreted using computer simulations of pursuit steering laws observed in insects and mammals. A comparison of the empirical and modeling data indicates that falcons use cues due to the apparent motion of prey on the falcon's visual field to track and capture flying prey via a form of motion camouflage. The falcons also were found to maintain their prey's image at visual angles consistent with using their shallow fovea. These results should prove relevant for understanding the co-evolution of pursuit and evasion, as well as the development of computer models of predation and the integration of sensory and locomotion systems in biomimetic robots. KEY WORDS: Predation, Pursuit-evasion, Avian vision, Falcon, Motion camouflage INTRODUCTIONHow predators track and capture their prey poses a fundamental problem in animal behavior that combines sensory perception, neural computation and locomotion. Empirical studies in combination with computational modeling (Pais and Leonard, 2010;Reddy et al., 2006;Srinivasan and Davey, 1995) have identified pursuit strategies used by insects (Olberg, 2012), bats (Ghose et al., 2006), dogs (Shaffer et al., 2004), fish (Lanchester and Mark, 1975) and humans (Fajen and Warren, 2004;McBeath et al., 1995). However, no empirical studies have addressed how falcons and other birds pursue flying prey, mostly due to the difficulty of recording their 3D flight trajectories in the field. The pursuit strategies used by birds have evolved in the context of their unique flight capabilities, as well as their need to pursue rapid, erratically moving prey in complex environments. Understanding their methods for tracking and following rapidly moving objects should provide inspiration for the design of unmanned aerial vehicles (UAVs) and other biomimetic robots.Stereoscopic video methods successfully used to study flocking (Ballerini et al., 2008a;Cavagna et al., 2010;Cavagna et al., 2008) are challenging to apply to this problem because of the wide geographic areas covered and the rapid, unpredictable motion of both predator and prey. However, bird-mounted sensors offer new opportunities for this field. While miniaturized, bird-mounted GPS sensors have been used to study navigation, flocking energetics and decision making in bird flocks (Biro et al., 2006;Nagy et al., 2010;Steiner et al., 2000;Usherwood et al., 2011), the 10 Hz data collection rate and 0.3 m spatial resolution of the GPS are of limited use in the present context. By contrast, miniaturized bird-mounted cameras have proved effective in studying the aerodynamics of avian flight (Carruthers et al., 2007;Gillies et al., 2011) and bird ...