Sorry it took so long to get back to you - did not have access to computer last week.
The caterpillars should be ok raised indoors as long as they are kept in the dark from sundown to sunup. I have not found my book that explains it better yet, to give you more details, but it has to do with the shortening of the days as fall comes.
As I remember it, during the longer days of summer a monarch caterpiller develops normally sexually and will produce eggs and mate and then die eventually of old age. These are not the ones that migrate to Mexico and other overwintering grounds. As the days grow shorter in the fall the newly emerged butterflies do not mature sexually and this triggers the instinct to migrate. The ones who make it to the overwintering grounds do not mature and mate until the days start getting warmer and longer in the spring. As they start migrating to the north they mature and mate and lay eggs and die, and it is their offspring that keep coming north. Hope this helps.
I would imagine that the worst that could happen with the ones you have raised so far is that they would mature normally and reproduce and it will be their offspring that migrates. You can continue to raise them indoors, just don't expose them to artificial light once the sun is down, and they should go through a normal cycle when they are released. Breeding if they are meant to breed and migrating if they are meant to migrate.
Funny you should mention bears and racoons, as that is the very reason I have not put my clothesline out with baggies this year. The bears have been playing havoc on my regular seed bird feeders, and have destoyed and or carried away four feeders since late spring, and have bent two sherpherd crooks right down to the ground. And the racoons have gotten after my hummingbird feeders several times this year also.
Today at noon my hubbie saw something black out of the kitchen window and was watching it because he thought it was one of our black kitties, and next thing I knew he yelled and told me to look out the window and there was a huge black bear snuffing around my birdfeer post and then it shuffled off into the woods as if he owned the place. (Which he does when he is in the yard! ha ha! At least neither one of us is gonna argue the point with him.) We have seen signs that he makes regular visits to the yard but this is the first time we have seen him personally. It was pretty awesome to see but I would just as soon he restricted his visits to nocturnal so I can be in my yard during the day.