I use a special transponder that I use to track hogs. It goes off 4 times a day at 7 and 8 a.m. and 5 and 6 p.m. It is called a feeder. Put up a game camera and you will get a lot more info than a transponder.

In all seriousness I have a female friend that tracks turtles in the ocean with a gps transponder with all kinds of gizmos. They would work great but they are a tad pricey at 16,000 dollars each. But they are very accurate.