I've never seen that photo before - good find! What looks like a track is I believe, the walking path for visitors. The foundations and parts of the chimney of that house are still there and easily found.
foundations by
mr. rollers, on Flickr
Hi all, I'm the guy who took the color photos of the old zoo (originally posted a page or so back above) back in the 80s when the zoo was first re-opened to the public. Glad you found and shared them! They were taken with an Olympus Stylus point & shoot 35mm camera, so naturally there is no exif or GPS data (only that from the flatbed scanner used to scan the prints).
As you can see, it was pretty overgrown and dilapidated back then. A lot was subsequently changed - a lot of the old buildings were torn down - so it's hard to recognize the exact locations. A new restroom building was also put up across from the stone cages.
The fire of 2007 burned right up to the old zoo, but as far as I'm aware, didn't damage or destroy any existing structures.
There's also a fascinating film on Vimeo called "The Cal Arts Story" (well worth a watch on its own) that contains a scene about 7:25 in that I'm pretty sure was shot at the old zoo.
https://vimeo.com/11955096