A Chameleon’s Skin Changes with Its Sleep Cycle

Brain oscillations during sleep could serve to protect animals from surprise attacks by predators.

By: Simon Koechlin

Published: June 4, 2026

Sleep still holds many secrets. But an international research team has shown that a key rhythm of our sleep is significantly older than previously believed. By recording brain activity in humans, rats, pigeons, and seven species of lizards—including geckos, iguanas, and panther chameleons—the researchers found that all of these species cycle through sleep phases marked by extremely slow brain oscillations.

The intervals of these "infraslow" rhythms span from roughly 50 seconds to two minutes and are coupled with autonomic bodily functions, including eye movements, muscle tone, heart rate, and respiration rate.

"When their sleep is less deep, this might allow an animal to be more aware of its surroundings."
— Markus Schmidt

This link is especially striking in panther chameleons, whose skin brightness visibly changes during sleep in synchronization with their brain oscillations. According to Markus Schmidt, a sleep researcher at Inselspital Bern involved in the investigation, these cycles likely cause rhythmic variations in blood vessel oxygen levels in the skin, which in turn alter the light-reflecting properties of pigment-bearing chromatophores.

These infraslow oscillations take place during non-REM sleep—a phase typically associated with low brain activity. While their primary biological function continues to be investigated, researchers hypothesize that these transient surges in neural activity keep animals from being caught off guard by predators, granting brief windows of heightened sensory awareness.

• Original Article: Horizons – The Swiss Research Magazine

• Underlying Study: Bergel, A., et al. (2025/2026). Sleep-dependent infraslow rhythms are evolutionarily conserved across reptiles and mammals. Nature Neuroscience, 29(3), 543–550.