My wife is a sucker for stray mutt puppies that wander into the yard. We had five of these yard dogs at one point. The second to last that wandered in and took up residence was a pit bull/setter cross. Nice guy when things were calm but far to aggressive. A sister to three of the mutts that ended up in my yard ended up with a family up the street. They thought it would be cute to bring her down for a reunion when they were about 4 years old. Needless to say, it was a six on one holocaust (5 yard dogs and my Australian Sheppard). Got the crap bit out of me the pit bull bull/setter and ended up breaking the whole thing up with a cattle prod. Cost me a couple hundred to get the other dog sewed up and I butterflyed my own self. Fast forward a few weeks, he had the UPS guy cornered. Fast forward a few more weeks, he went for a friend that came to help me pull a calf. Bear in mind that during this time I had worked with him to try to correct the behavior but I'm not here 24/7. He dropped it as fast as he learned it. Collar on, me in sight, he was an angel. Me not here, an absolute terror for the regular 'strangers', UPS, mailman, meter reader, house keeper. The last aggressive move on my Buddy was the last straw. End of story, doggie heaven. I know I'll get flamed but I don't care. He had a good life, albeit abreviated. Square meals, squirrels to tree, 2 acres to crap on and a warm place to sleep. Just way too agressive.
For the potential flamers, we always try to place these strays. We've had about 10 or 11 in the last several years but no one wants them. Some have gone down to Parvo before we could get them innoculated, some were just sickly inbreeds. All the rest are neutered, current on meds and GD county tax.
Flame away, I'll likely ignore you.