Many species of ants have multiple nests, older ants may never return to the main nest, but relay information about good finds to younger ants who have contact with the queen and brood. This is a natural barrier to keep poisons and pathogens from reaching the most sensitive and irreplaceable members of the colony.
So to track ants you may first need to find the outpost, then track those going from outpost to the main nest.
futurebird