The transmitter is programed to turn itself on and off to conserve battery life. It has a saltwater switch so that it only transmits while it is exposed to air. The signal is too weak to penetrate water. This limits the use of satellite technology to species that spend time at the water's surface or come to the surface regularly. Therefore these devices are particularly appropriate for studying marine mammals that must come up to breathe.
Battery life affects how much and the quality of data received from a tag.
Battery life varies depending upon size, temperature, depth or pressure and corrosion by the saltwater. Also, data transmission uses up the battery. Therefore, the more transmissions the shorter the battery life. WhaleNet has used various batteries with its tags in an effort to extend the life expectancy of the tag. Our tags have lasted up to nine months.