I believe Mastiffs wer originally bred to keep poachers off the kings lands in England. This practice was stopped when the Mastiffs started killing the poachers.
They will often hold intruders in a corner for an entire day until owners return. As my close friends dicovered when returning to their providence r.i home and found an intruder badly injured and pinned in a corner by there two english mastiffs. Needless to say it was the only incident they ever had at that address.
They can be great dogs when raised around children from a pup. These 2 were sketch and I never left my kids unattended around those dogs when they were young (kids).
But definately a better option than my retriever. I have yet to see a duck in my op, let alone shot one for my dog to go get. I bet he would fuck up some buds pulling the fowl out of the reeds......i mean weeds.