A noninvasive photoplethysmographic sensor platform for mobile animals such as small rodents, namely rats and mice is useful such as in a laboratory research environment. The noninvasive photoplethysmographic sensor platform may be a collar which provides an easily affixed, adjustable attachment mechanism that encircles the animal, such as the neck. The neck of the animal provides several particular advantages as a sensor mounting platform for photoplethysmographic sensors. For pulse oximetry, the neck location will provide significant blood flow under all conditions. For small mammals, such as rats and mice, transmittance pulse oximetry through the neck of the subject remains possible. The neck mounted collar also offers inherent bite resistance to the sensor platform.