One possible scenario that has been bugging me for a week now:
The day when mankind’s continual expansion and decimation of natural habitats result in micro-pockets of forests + accelerated shrinkage of existing fragments (some of which we call reserves, national parks, protected areas) as a result of the lack of buffer zones.
"At what point does that become captivity? A 10000 m fence? 1000 m fence? What if veterinary care is provided? Or extra food? Or the animal is left alone, but has a tracking collar attached?"