There could be two types of Zoos. Using human analogy, city zoo and wild-life reserve. City zoo has a few animals under very tight control, and they can live in a perfect simulation of the intact world, like fishes in tank. Wild-life reserve has more animals, but less protected from wrong observations. E.g. hunting grounds.
The second type is more probable based on anthropics, as it includes many more observers, and if we are in a zoo, it is probably of the second type. It may explain UFO observation, or, if we discard UFOs, it is an argument againt zoo.
There could be two types of Zoos. Using human analogy, city zoo and wild-life reserve. City zoo has a few animals under very tight control, and they can live in a perfect simulation of the intact world, like fishes in tank. Wild-life reserve has more animals, but less protected from wrong observations. E.g. hunting grounds. The second type is more probable based on anthropics, as it includes many more observers, and if we are in a zoo, it is probably of the second type. It may explain UFO observation, or, if we discard UFOs, it is an argument againt zoo.