This is specifically not thermal (blackbody) radiation, which is negligible at the visible frequency range for mice at these temperatures. The researchers find

This is specifically not thermal (blackbody) radiation, which is negligible at the visible frequency range for mice at these temperatures. The researchers find a difference in visible wavelength emission between living and dead mice at the same temperature This point is addressed on page 2 of the paper. Paper is accessible on bioarxiv: https://www.biorxiv.org/content/10.1101/2024.11.08.622743v1 https://www.biorxiv.org/content/10.1101/2024.11.08.622743v1