Abstract: An automated system and method for obtaining early detection of biological changes or events by assessing core body temperatures that precede the events within individual animals in a production herd. The system and method may monitor the animals, assess the data acquired with a variation from a diurnally compliant baseline in the selection of or use of data monitored, and provide a timely communication to owners and operators as deemed appropriate. An assessment may establish variations from the baseline, compensate for ambient conditions or identify patterns of variation, that anticipate estrus, ovulation, illness, calving or other biological events throughout the herd population. The assessment may include signal processing techniques that substitute for baseline establishment, or be used in combination with baseline variation assessment.