A method and apparatus for photoplethysmographic measurements from non-human species is disclosed. The extinction of light by hemoglobin, as a function of wavelength, varies as a function of the species of the subject being monitored. The calibration of a photoplethysmographic device should therefore also vary dependant upon the species of the subject. The photoplethysmographic device of this invention includes calibrations specifically designed to provide accurate readings on non-human subjects.