IIRC, Black Bears are the #1 predator when it comes to killing Elk calves each year.
Apparently the bears come out of hibernation, head for some fields to load up on grass,
etc. to get the stomach juices working again, and then they start looking for some
meat to fill a very empty hole.
If you're in the timber country and working a single spot, stringing a bunch of cans
together (lot's of 'em!) and running those strings to surround your area about 50'
off. If the bears take off when they hit the cans, great, but if not at least you won't
be surprised at 0300!