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.

Differential locomotor and predatory strategies of Gondwanan and derived Laurasian dromaeosaurids (Dinosauria, Theropoda, Paraves): Inferences from morphometric and comparative anatomical studies

“…Extant long‐legged and predominantly terrestrial birds that forage on the ground and hunt small prey include the seriemas (Cariamiformes) and the Secretary Bird (Falconiformes). The Secretary Bird kicks and stamps on the prey until it is wounded or incapacitated, and then takes it with its beak (Kemp and Kemp, ; Kemp, ; Portugal et al ). By contrast, the Red‐legged Seriema ( Cariama cristata ) takes the prey with its beak and hits it on the ground with sudden movements of the head until it is injured (Boyle, ).…”

“…Secretary Bird kicks and stamps on the prey until it is wounded or incapacitated, and then takes it with its beak (Kemp and Kemp, 1978;Kemp, 1995;Portugal et al 2016). By contrast, the Red-legged Seriema (Cariama cristata) takes the prey with its beak and hits it on the ground with sudden movements of the head until it is injured (Boyle, 1917).…”

An Overview on Principles for Energy Efficient Robot Locomotion

“…To understand the principles of bipedal gait, it is essential to combine perspectives from biomechanics, sensorimotor control and engineering. Recent studies have focused on measuring movement biomechanics over simple terrain features, such as obstacle negotiation and single downward steps Blum et al, 2014), gait transition dynamics of ostriches moving freely in an open field , and leg loading during kicking and locomotion in the snake-hunting secretary bird (Portugal et al, 2016). These studies provide insight into locomotor control strategies by comparing steady and transient movement tasks, and investigating potential trade-offs among factors such as speed, stability, robustness and economy.…”

Scaling of avian bipedal locomotion reveals independent effects of body mass and leg posture on gait

“…Current scaling analyses do not account for the vast diversity of avian ecology, life history and locomotor behaviors. In this Review, we have focused on the well-studied striding bipedal gaits of walking and running, but birds use their legs for a diverse range of behaviors, including hopping and skipping, jumping for flight takeoff, arboreal locomotion, swimming, water running and scratch preening (Abourachid and Höfling, 2012;Biewener and Corning, 2001;Heers and Dial, 2015;Portugal et al, 2016;Provini et al, 2012aProvini et al, ,b, 2014. Although most birds use striding gaits during some part of their life history, other behaviors are undoubtedly ecologically important.…”