An animal monitoring telltale device including a receiver attached to the animal and a transmitting device inserted in the animal subcutaneously or in a cavity at a location indicative of the deep body temperature of the animal. The implanted transmitter will send a signal to the proximately located receiver indicative of a monitored condition in the animal. In addition, the signal is encoded with an identification signal providing ownership information and theft protection. The receiver is preferably secured to an ear tag which tag includes a light or other visual signal indicative of a predetermined value of the measured condition. The receiver may also be operatively connected to a re-transmitter for re-transmitting a higher power signal to a remote monitoring location.