Bristol Zoo had scales in their old Gorilla House which was purpose built for 'Congo' and 'Josephine' in the 1950's. The platform was inside (obviously!) the outdoor cage and the dial (like an old fashioned weighing machine) was outside. Mind you, I never saw the Gorillas use it voluntarily but I think they could be coaxed onto it with food. The female 'Josephine' was so obese its probably better she didn't...
I think they routinely scatter food over the scales here. I saw Anette sitting on them on each day I was there. I believe Paignton has scales for the orangs in the den at the back of the ape house and food is used as an enticement. Presumably the gorilla scales are in Kumbuka's old den. Duchess, the African elephant, has to walk over hers to get in and out of her house, but the readout isn't always switched on.
