An apparatus and methods for detection of estrus and optimal time for embryo transfer or artificial insemination in animals. An arched polycarbonate housing is attached to an animal. A circuit board is disposed within the housing. A rechargeable battery mounted on the circuit board provides power to the apparatus. A switch mounted on the circuit board is actuated when a breeding behavior occurs. A controller mounted on the circuit board detects actuations of the switch to generate data indicative of breeding behavior. A transmitter transmits data indicative of breeding behavior to a remote receiver.