I guess the advantage over a dog is that, should it indeed have a detectable effect, and a sufficiently noticeable one, one could fly a drone (even, perhaps, a

I guess the advantage over a dog is that, should it indeed have a detectable effect, and a sufficiently noticeable one, one could fly a drone (even, perhaps, a Global Hawk; I don't know how precise the pictures it takes are), and just scan huge swaths of forest at once, much faster than one could with even a hundred dogs. But that's a lot of ifs.