Sand swimming lizard: sandfish

TL;DR

This study combines high-speed x-ray imaging and numerical modeling to analyze how the sandfish lizard swims within granular media, revealing unique undulatory propulsion mechanisms below the surface.

Contribution

It introduces a validated numerical model of the sandfish's subsurface swimming behavior in granular media, enhancing understanding of its locomotion dynamics.

Findings

Sandfish uses sinusoidal waves for propulsion underground.

The model accurately predicts flow fields and forces during swimming.

Sandfish can reach speeds up to 1.5 body lengths per second.

Abstract

We use high-speed x-ray imaging to reveal how a small (~10cm) desert dwelling lizard, the sandfish (Scincus scincus), swims within a granular medium [1]. On the surface, the lizard uses a standard diagonal gait, but once below the surface, the organism no longer uses limbs for propulsion. Instead it propagates a large amplitude single period sinusoidal traveling wave down its body and tail to propel itself at speeds up to ~1.5 body-length/sec. Motivated by these experiments we study a numerical model of the sandfish as it swims within a validated soft sphere Molecular Dynamics granular media simulation. We use this model as a tool to understand dynamics like flow fields and forces generated as the animal swims within the granular media. [1] Maladen, R.D. and Ding, Y. and Li, C. and Goldman, D.I., Undulatory Swimming in Sand: Subsurface Locomotion of the Sandfish Lizard, Science, 325, 314, 2009