We used to have a problem with bears at the restaurant I worked at in Haliburton county a couple years ago (Dorset, Ontario...I'll bet you can guess which restaurant it was

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I got quite a fright in the late spring when taking the garbage out at the end of the night. I came around the corner of an outbuilding with a large bag of kitchen garbage to find a LARGE sow in the process of ripping top off of the the steel bear proof bin. "HEY!" says I. She stops ripping the bin apart and jumps down to the ground, closing the distance between us to about 15 feet. I didn't like the way she was rumbling and pawing. Then, peripheral vision shows me her cub, about 6 feet to my left next to the grease bin. "HOLY F*%K!" I said, throwing the bag of garbage in her general direction and booked it back inside. I went out later, and the bag of garbage was gone. This was my closest encounter, but one of many by the staff at the restaurant. I also had the opportunity to watch a large boar jump on the grease bin until it tipped, and kept slurping away at the oil despite being hit with a large block of maple firewood. Pretty common occurence in northern Ontario, but I have to stress the point that she was NOT afraid of me.
The boss had called the MNR numerous times, and they had attempted to live trap on the property and surrounding property, with no success. Apparently, they're to smart to walk into the gian cake and flip the switch. She asked me if i could "take care of the problem" if it happened again. Sure, I said. She asked me what kind of gun i would use, and i told her that one good shot from my .308 would probably solve the problem of one bear. She didn't want the noise, though, and requested that i might use my crossbow. My reply? Not a f*#%in chance. 10 yards from the ground in the dark with a pissed off momma with cubs? Might take her a half hour to die after being shot? No thanks....
Bottom line, in my opinion, if there is a bear in the yard, you can't otherwise frighten it off, and you have reason to fear damage or injury to yourself, other people, or your property, then blast away. I know my father and father in law had dispatched dozens of problem bears in the past, and this reasoning worked well enough for them. Just make sure to phone the mnr afterwards to let them know, "Hey, come get this dead bear off of my lawn."