The tagging I'm familiar with uses collar transmitters that are on the animals neck.
The animal is tracked with a direction finding antenna from an aircraft or truck.
This method is used by wildlife scientists.
Interesting stuff, but pricey, not just in initial equipment but in support and man hours as well. I can't see it as much of a viable option for most feral colonies as a matainence tool, it is hard enough to raise enough man power and money for basic vet care & feeding.