Abstract: An animal birth detector is described comprising apparatus attached in the proximity of the animal's vulva for detecting the birth of offspring by monitoring the swelling of the vulva during the period prior to and during delivery of the newborn. More specifically, the animal birth detector comprises a unitary device containing a transmitter attached to the skin proximate one side of the animal's vulva, the transmitter utilizing a reed relay switch to sense the proximity of a permanent magnet located in the device. As the vulva dilates at time of delivery, the magnet is moved out of the magnetic field sensing area of the reed switch, turning on the transmitter whose transmissions are received by a receiver monitored by an attendant.