Apparatus and method for managing animals such as but not limited to livestock. In some embodiments, an ear tag assembly has a main body, a backing member and a shaft that extends through an aperture through an outer ear of an animal to interconnect the main body and the backing member. A primary temperature sensor obtains an outer ear temperature of the outer ear. An ambient temperature sensor obtains an ambient temperature of a surrounding environment external to the animal. A control circuit receives the outer ear and ambient temperatures and determines a state of the animal responsive to a comparison of the outer ear temperature and the ambient temperature over a selected time interval.
