A terrain treadmill to study animal locomotion through large obstacles

TL;DR

This paper introduces a terrain treadmill that allows high-resolution, long-duration study of animal locomotion through large obstacles, overcoming previous scale limitations in terrain research.

Contribution

A novel terrain treadmill design enables detailed, large-scale observation of animal movement in complex 3-D terrains within a controlled lab setting.

Findings

Discoid cockroach moved 67 meters over 25 minutes on obstacles.

Animal maintained proximity to center 83% of the time at high speeds.

The system captures diverse locomotor behaviors and interactions.

Abstract

A major challenge to understanding locomotion in complex 3-D terrain with large obstacles is to create tools for controlled, systematic lab experiments. Existing terrain arenas only allow observations at small spatiotemporal scales (~10 body length, ~10 stride cycles). Here, we create a terrain treadmill to enable high-resolution observations of animal locomotion through large obstacles over large spatiotemporal scales. An animal moves through modular obstacles on an inner sphere, while a rigidly-attached, concentric, transparent outer sphere rotated with the opposite velocity via closed-loop feedback to keep the animal on top. During sustained locomotion, a discoid cockroach moved through pillar obstacles for 25 minutes ($\approx$2500 strides) over 67 m ($\approx$1500 body lengths), and was contained within a radius of 4 cm (0.9 body length) for 83% of the duration, even at speeds of up to 10 body length/s. The treadmill enabled observation of diverse locomotor behaviors and quantification of animal-obstacle interaction.