Abstract: Disclosed is an apparatus for estrous detection, analysis and telemetric communication of a signal indicating estrus. The apparatus is specially adapted for surgical implantation on the hindquarters of cattle or other animals which exhibit selective standing heat behavior often termed standing to be mounted. The apparatus which is implanted under the hide of the animal, comprises a self contained power source, a force responsive sensor, a controller, a transmitter, an antenna, and a fluid-tight capsule which surrounds the other elements of the apparatus. The apparatus operates by sensing force applied during sustained mounting of an animal which is in estrus by another animal in the herd. The implantable apparatus analyzes the duration of mounting to discriminate standing heat mountings from shorter duration spurious mountings which routinely occur in cattle herds.