Are owls technically capable of making a full head turn?

Area of Science:

• * Comparative biomechanics
• * Vertebrate anatomy and physiology
• * Avian locomotion and kinematics

Background:

• * Owls possess a remarkable ability for extreme head rotation.
• * Understanding the biomechanical basis of this 360° head turn is key to avian functional morphology.

Purpose of the Study:

• * To analyze the three-dimensional configuration of owl necks during extreme head rotation.
• * To quantify vertebral joint mobility and its contribution to the 360° head turn.
• * To assess the role of specific neck muscles in facilitating this movement.

Main Methods:

• * Utilized the Joint Coordinate System to measure planar axial rotation (AR), lateral, and sagittal bending in each vertebral joint.
• * Analyzed vertebral joint angles during a simulated 360° head turn.
• * Evaluated the shortening capacity of the mm. intertransversarii muscles.

Main Results:

• * Owl neck joint mobility is generally within typical avian ranges, with extended AR being a notable exception.
• * The 360° head turn is achieved by combining planar motions, with joints often exhibiting counter-lateral bending or rotation.
• * The mm. intertransversarii muscles do not need to shorten beyond 50% of their capacity for the full head turn.

Conclusions:

• * Owl head rotation is a complex interplay of standard joint movements, enhanced by counter-balancing.
• * The observed joint configurations likely preserve visual function during extreme rotation.
• * The study introduces a novel CT scan-based method for measuring intervertebral angles, applicable to various tetrapods.