I took one down with a single 230gr SilverTip HP out of a S&W 4506. It took about 2 seconds to die.
Did I mention it had already lost the use of its legs from a car hitting it and I was 6 feet away? As long as you can arrange to have a speeding car nearby, the .45 shouldn't give you any problems. ; )
Not being a hunter, I had no idea where that thing's heart was, so I just took a head shot, which worked out fine.
And, yes, I realize I'm no help at all. Sorry. I just don't get to tell that story in most social settings.