Monster Paradise

Humans, be it a powerhouse or a common man, had to breathe.

The difference in the pace and intensity of the breathing could roughly determine a person's condition. At least, Tang Ling's Precise Instinct could discern that. 

Humans generally breathed with the mouth and nose, so if something breathed through its body, what could it be?

More precisely, this particular thing breathed using every follicle on its skin and through the retraction of muscles. The body was able to function as the mouth and nose.

Tang Ling thought he heard wrongly at first, but his Precise Instinct was able to tell the subtle differences. The noise of the breathing was very different from that using the nose or mouth.

Tang Ling even triple-checked and was certain that more than three prisoners were breathing through their bodies and not their noses or mouths.

If such things were not monsters, what would they be?