Hunting land is categorised in a number of ways which may restrict who is allowed to hunt. The category a parcel of land falls into can be identified by the signs prominently displayed on the boundaries.
Chasse gardée means that hunting is the main activity undertaken on the land, and it is managed to maintain a good population of game. Non-hunters are not welcome on this land as they will disturb the game. Hunters need the permission of the landowner to enter.
Chasse réservée means that unless you have permission from the owner you can't hunt there. In practice it usually means the land is reserved for the local communal hunt.
Chasse privée signs mean an estate of more than 20ha which you cannot hunt on unless you have the owner's permission. These are usually the private hunting estates, which operate more or less according to the wishes of the owner and cater for paying clients.
Chasse interdite means that the land has been officially registered as withdrawn completely from any hunting activity. It means that even the landowner cannot hunt on the land, and you very rarely see this sign here.
No sign at all on a parcel of land means that theoretically anyone with a hunting licence can hunt there. Strictly speaking they are required to notify the landowner in advance in writing that they wish to cross the land but my impression is that most hunts obtain a verbal agreement only, and do not deliberately antagonise landowners by entering properties where they are not welcome. Since theoretically you cannot discharge a gun within 150m of any building (including garden sheds and caravans) in practice the hunt is not very likely to cross your backyard even if the quarry does. (I have it on good authority that the 150m rule is routinely broken, but even so, the hunt is not generally conducted on land where it is not welcome.)
Temporary signs on the roadside saying Attention! Chasse en cours mean that the hunt is currently operating in that area. You need to be careful of dogs or game dashing across the road. Occasionally you may encounter a mounted huntsman, in which case you should give the horse a wide berth at a slow even speed. Usually the huntsmen are on foot though and wearing hi-viz vests. If they are carrying a gun it must be uncocked or broken. If the hunt is only just starting beware of panelvans slowing down and turning off.
The hunting season opens in Indre et Loire today. For the rules about what can be hunted, how and when throughout France, go to the Féderation Nationale des Chasseurs website.