Injectable transmitters are provided that can include a body with the body housing a power source and an oscillator, the injectable transmitter also including an antenna extending from the body, the body and antenna being of sufficient size to be injected through a 9 gauge needle. Radio frequency transmitters are provided that can include a body extending from a nose to a tail with the body housing a power source and RF signal generator components. The power source of the transmitter can define at least a portion of the nose of the body. The transmitters can have an antenna extending from the tail. Methods for attaching a radio frequency (RF) transmitter to an animal are provided. The methods can include providing an RF transmitter and providing an injection device having a needle of gauge of 9 or smaller; providing the RF transmitter into the injection device; and providing the RF transmitter through the 9 gauge or smaller needle and into the animal.