It is entirely possible for the need zone you discovered for a Moose (for example) is also used by rabbits, Whitetail or Blacktail deer or ever bears. Also, the thing about need zones is that the info pertaining to it shown on the map reflects the last species to use it.
The icon on the map only designates the general area of the need zone. Need zones may cover an area 200 meters in diameter not just the one little place you checked out a weed or footprints or put the spot on an animal. Need zones stay in place once you either investigate a need week or put the spot on an animal that is feeding or drinking at it (provided of course you don't kill max out the hunting pressure in it). I believe that if you look in the bottom right of the map legend the time frame is displayed when you move the pointer over the need zone.
