American zoos are the worst offenders.
Years ago, when we visited a zoo in our state, two of the
big cats were doing a sort of repetitive routine that
looked like a circus routine. I asked if they had been in
a circus. Someone told me, “No. This is simply manic
behavior from having been confined in a cage for so long.”
Nashville has one where they’re kept outside in a larger
outdoor situation. Better but not ideal.
When our son was little, the zoo in Memphis kept their
hippos in a pool with horizontal “restraining” bars above
them. Son was sort of “energetic” back then; and ran in
under the bars - almost fell into the pool before I could
get oriented to my surroundings. Come to think of it; there
were other less than ideal situations lots of places - but
I didn’t complain. (Back when I was a kid; there was an
old filthy rich woman who used to have her chauffeur drive
around that zoo near the sandbox and kidnap little kids and
adopt them out to rich parents. My parents always watched
me like hawks.)