I too have no expertise here, but I've known quite a few rodents. So... my amateur take:
I do not think that the area would necessarily need to be cleared of debris first. Rats can get places people would never imagine they could quite easily.
What I did find to be consistent with rodents is the difficulty in getting them to use set search patterns and such. Rodents go where and how rodents go, and I've never found it possible to teach them set routes. They get a whiff and tend to go right at whatever they smelled in contrast to dogs who can be taught to take set routes/patterns.
The "distance from the nose" wouldn't matter. Rodents can often smell stuff that's around a mile away... a few inches of dirt (most landmines are under fewer than 25cm of dirt, anti-tank mines under fewer than 30cm) wouldn't be sufficient to deter them.
Reliably signaling humans depends upon the particular rodent. Rodents have personalities, and they will often make very particular signals to their people in response to particular things. Reliably enough to bet a life on it? Not sure, but I don't think they'd be terrible in that regard.
I do not think that the area would necessarily need to be cleared of debris first. Rats can get places people would never imagine they could quite easily.
What I did find to be consistent with rodents is the difficulty in getting them to use set search patterns and such. Rodents go where and how rodents go, and I've never found it possible to teach them set routes. They get a whiff and tend to go right at whatever they smelled in contrast to dogs who can be taught to take set routes/patterns.
The "distance from the nose" wouldn't matter. Rodents can often smell stuff that's around a mile away... a few inches of dirt (most landmines are under fewer than 25cm of dirt, anti-tank mines under fewer than 30cm) wouldn't be sufficient to deter them.
Reliably signaling humans depends upon the particular rodent. Rodents have personalities, and they will often make very particular signals to their people in response to particular things. Reliably enough to bet a life on it? Not sure, but I don't think they'd be terrible in that regard.