Five years have passed since the Beary Triplets came to ABR and created much chaos and merriment with their shenanigans. Typical of these little mischief-makers was the time that they conquered one of the Forbidden Trees. Their conquest was captured in a video that you can see by clicking here
As you can see, the original shields on the trees that are too close to fences or need protection from cubby claws. After these little cubs proved that the metal shields were able to be overcome, the curators switched to the hard plastic shields that are in use now.