I can't remember much, if anything about belle vue zoo, I was just a toddler the last time I went. Stony family lore says that the lion did exactly what you said and let out a stream of piss like a fire hose.
My mum was unlucky with zoos. On another occasion at belle vue, she bent over to see to me in my buggy and a bloke opened his raincoat right in front of her face and exposed himself. I used to piss myself laughing when my mum recounted this tale because she always ended with "and it was that big" a look of horror on her face whilst she held open her arms like a fisherman describing the one that got away.