Animals in the zoo are distressed, they do not have enough space, most of them live in small, concrete floored
cages.Many of these animals show signs of "stereotypic behavior" which is common in animals that exist
in cages without anything to stimulate their mind.
Signs of "stereotypic behavior" are:
pacing, circling, neck twisting, bar licking, bar biting, tongue playing,
coprophagia, overgrooming, self-mutilation or abuse: tail biting, leg chewing, head bashing...
Wikipedia, Stereotypic behaviour »
Cages are small and visitors are to close to the animals.Visitors often disturb animals by feeding them, climbing on fences, taking photographs with flashes, shouting, tapping on bars, etc.