Mixed gaits in small avian terrestrial locomotion

Area of Science:

• Biomechanics
• Animal Locomotion
• Comparative Physiology

Background:

• Traditional locomotion studies categorize gaits discretely (e.g., walking, running).
• Emerging evidence suggests animals, particularly birds, may utilize mixed or switching gaits during steady-speed locomotion.
• Understanding gait flexibility is crucial for comprehending diverse animal movement strategies.

Purpose of the Study:

• To investigate gait utilization in various bird species.
• To determine if birds employ mixed gaits more frequently than previously assumed.
• To explore the mechanics and stability of mixed gaits using bio-inspired models.

Main Methods:

• Analysis of over one million frames of center of mass motion in quail, oystercatcher, northern lapwing, pigeon, and avocet.
• Combination of large-scale automated motion analysis with numerical simulations.
• Development of a bio-inspired model based on quail locomotion parameters.

Main Results:

• Birds do not exclusively use walking mechanics at low speeds or running mechanics at high speeds.
• Mixed gaits, involving combinations of walking and running mechanics within steps, are frequently employed.
• Mixed gaits are used more often than walking and nearly as often as grounded running.
• Two stable types of mixed gaits were identified in simulations: asymmetrical and alternating leg mechanics.
• Parameters for mixed gaits largely overlap with those of grounded running, suggesting easy transitions.

Conclusions:

• Locomotion in birds is more flexible than discrete gait categories suggest.
• Mixed gaits represent a significant and common mode of locomotion in the studied bird species.
• The overlap in parameters between mixed and running gaits indicates that minor perturbations can trigger gait switching.