A continuum of sleep and shallow torpor in fasting doves

Fasting doves entered shallow torpor during nocturnal sleep. Body temperature dropped lower each successive night by 1 degrees to 3 degrees in parallel with diminished rapid-eye-movement sleep until torpor was composed almost entirely of slow-wave sleep at a body temperature of 30 degrees to 32 degrees C. Shallow torpor in doves, as in mammals, thus appears to lie on a metabolic continuum with sleep.