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How Small, Arboreal Lizards Run on Water: Surface Tension, Morphology, Behavior, and Kinematics
Philip J Bergmann1, Samantha E Reed1
1Clark University, Department of Biology, 950 Main Street, Worcester, MA 01610, USA.
Integrative and Comparative Biology
|April 9, 2026
Summary
Small lizards, Anolis sagrei, can run on water by adjusting their movements. Reducing water surface tension decreased how often they ran, but their speed and performance remained the same due to kinematic adjustments.
Area of Science:
- Biomechanics
- Vertebrate locomotion
- Surface interactions
Background:
- Most water-walking animals are small invertebrates; larger vertebrates are specialized.
- As animal size increases, surface tension's role diminishes, with inertial mechanisms becoming dominant.
- Anolis sagrei lizards, with adhesive pads, are studied for their water-running capabilities.
Purpose of the Study:
- Investigate how Anolis sagrei lizards run on water.
- Quantify the effect of reduced surface tension on water-running frequency and performance.
- Analyze kinematic variables and morphological features influencing water-running performance.
Main Methods:
- Behavioral observations and high-speed video analysis.
- Experimentation with reduced water surface tension using a surfactant.
- Comparison of running performance and kinematics on normal and treated water.
- Testing the influence of morphological features on performance.
Main Results:
- Reduced surface tension decreased the frequency of water running (17% to 9% of trials).
- Performance metrics (velocity, Froude number, body out of water) were unaffected by reduced surface tension.
- Lizards employed faster limb slaps and shorter undulatory wavelengths with reduced surface tension.
- Increased stride and undulatory frequencies were key to enhancing water-running performance.
- Morphological features did not significantly impact water-running success.
Conclusions:
- Anolis sagrei lizards compensate kinematically for reduced surface tension, maintaining performance.
- Adjusting stride and undulatory frequencies are primary strategies for optimizing water-running.
- Behavioral frequency may explain discrepancies in previous studies on water-running vertebrates.
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