This is a very revealing photo as you can clearly see the back wall was added after the original Tecton structure was built. In fact, there are early photos of the polar bear pit where the orginal metal railings along the back of the enclosure in this photo (the right hand tecton current black bear enclosure) can be seen. They are identical to the bars in the photo on this forum of the old lion enclosure.
When the zoo opened this was originally the Tiger Enclosure with the Polar Bear enclosure in the middle and the Lion enclosure was where they have now got Sarah (Sumatran Tiger) as we can see very little as changed except the layered area is now flattened and a climbing frame been added
as you can see from this one, the same fencing was installed at the back of the left-hand side, only this was replaced with chain link, indicating its continuous use for cats since its inception.
The right-hand enclosure however, was clearly modified for bears with the construction of the back wall which was painted to resemble the rest of the tecton structure. Not having known Dudley until the 1980s, I make the assumption that the lions were moved out to the site of the current wild dog enclosure about the same time that the bear ravine stopped holding bears, and the resulting modification was to allow bears to be held in the right-hand tecton pit. However, I am intrigued to know why the bears weren't simply housed in the left-hand enclosure once the lions had moved out. Perhaps there was a break in them keeping tigers rather than the tigers being moved from the right hand pit into the left. Or perhaps the bears were kept for some time with a chain link fence in the right-hand enclosure before it was realised something sturdier was required.
What I would actually like to believe is that the zoo wanted the option of running the polar bears in the right hand enclosure, as there is a connecting door from their inside quarters into this exhibit.
Does anyone have the Dudley zoo memory I am searching for here?