The USDA Wildlife Services have been putting out the raccoon rabies oral vaccine baits and after those baits have been out for a while, they go into those areas and trap raccoons to see how many of them actually picked up and ingested baits that are bio-marked with tetracycline. This is done to ensure that enough vaccine baits are distributed to effectively vaccinate the raccoon population in the area that is treated. You can find more information about the program at the following website National Rabies Management Program
