I don't know, but it's in the Children's Farm area - I'd have thought it would be prefectly possible to convert it for guinea pigs or something similar if nothing else.
That's a different exhibit to this one though; the bush dogs/binturongs are over near the Australian area, while this is in 'La Pequena Granje' - Paradoxurus posted this shot of it in its raccoon days: http://www.zoochat.com/178/madrid-raccoon-enclosure-35042/
If there was more coverage over head, I could see this being a sloth exhibit. With a different entrance into there indoor enclosure and a couple of dead trees, I believe it would be fine for a single sloth or a pair.