Logic says that if you have done nothing to alter the environment of your property, yet there has been a highly significant decline in snakes occurring there, then it has to do with either a significant decline in local snake populations or the creation of a barrier outside your property. As the latter hasn’t happened, the local populations must have declined for some reason.
Without seeing the area it is impossible to assess what has changed in the environment. You have indicated that their has been no significant physical disturbance so one can only assume that it is a biological factor(s). Introduction of predators to the area are a likely culprit. Cats being allowed to roam and kittens being dumped to go feral are a distinct possibility. Foxes are often found in association with human habitation. If anyone has been baiting for rats, that can take its toll. Basically, by the sounds of it I don’t like your chances of attracting the snakes back, as I don’t think they are there to attract.
Still, if you want to try, set up the frog pond as indicated. Add an aviary or chook yard. Let the grass grow long. Ensure there are plenty of potential refuges, like stacks of six or more sheets of corrugated iron etc.
Blue
