The animals' boredom and suffering can be seen in the way they pace up and down the same area and sway back and forth. Some actually go mad with frustration. Some zoo enclosures mean that the inmates cannot even enjoy their most basic behavioural repertoire, including exercise, social interaction and bathing. When animals do find company, their world may be torn apart when cage mates are sold. Solitary and shy animals are often in enclosures with viewing from all sides, and even a window in the night quarters as well.
Visitors tap the glass of tanks, poke the animals, and are noisy and boisterous.
Some zoos admit that certain animals, like polar bears, simply shouldn't be there. For example, a polar bear's companion died. There she was left, in a zoo, her natural territory of hundreds of miles reduced to a few metres with an ice-flow painted on the wall, and rocks painted white. She is going mad, spending most of the day retracing the same steps again and again. Such pointless repetitive movements have also been noted in mentally ill people.