title: The fast and forceful kicking strike of the secretary bird.
abstract: The study of animal locomotion has uncovered principles that can be applied to bio-inspired robotics, prosthetics and rehabilitation medicine, while also providing insight into musculoskeletal form and function [1-4]. In particular, study of extreme behaviors can reveal mechanical constraints and trade-offs that have influenced evolution of limb form and function [1,2]. Secretary birds (Sagittarius serpentarius; Figure 1A) are large terrestrial birds of prey endemic to sub-Saharan Africa, which feed on snakes, lizards and small mammals [5]. They frequently kick and stamp on the prey's head until it is killed or incapacitated, particularly when dispatching larger lizards and venomous snakes [5]. The consequences of a missed strike when hunting venomous snakes can be deadly [5], so the kicking strikes of secretary birds require fast yet accurate neural control. Delivery of fast, forceful and accurate foot strikes that are sufficient to stun and kill prey requires precision targeting, demanding a high level of coordination between the visual and neuromuscular systems.
authors.affiliation: School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK. Electronic address: Steve.Portugal@rhul.ac.uk.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Portugal
authors.affiliation: Hawk Conservancy Trust, Sarson Lane, Weyhill, Andover, Hampshire SP11 8DY, UK; School of Biological Sciences, University of Reading, Berkshire RG6 6AS, UK.
authors.forename: Campbell P
authors.initials: CP
authors.lastname: Murn
authors.affiliation: Structure and Motion Laboratory, Royal Veterinary College, University of London, Hawkshead Lane, Hertfordshire AL9 7TA, UK.
authors.forename: Emily L
authors.initials: EL
authors.lastname: Sparkes
authors.affiliation: Structure and Motion Laboratory, Royal Veterinary College, University of London, Hawkshead Lane, Hertfordshire AL9 7TA, UK.
authors.forename: Monica A
authors.initials: MA
authors.lastname: Daley
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001696:Biomechanical Phenomena / Q000502:physiology*; D001717:Birds; D005247:Feeding Behavior / Q000502:physiology*; D008116:Lizards / Q000502:physiology; D008124:Locomotion / Q000502:physiology*; D011235:Predatory Behavior / Q000502:physiology*; D012911:Snakes