Zoos can have problems (see also this and this), as one would expect, when people try to cage nonhuman animals (animals) and take away their basic needs and freedom. However, there also can be problems when the animals themselves kill other animals and some, not surprisingly, escape.
I just learned of some very sad and apparently avoidable incidents at the UK's Bristol Zoo that happened in December. The article I read called "Rare warty pigs are lost when male eats his entire family at Bristol zoo" begins:
"A zoo lost some of its most endangered animals when a male warty pig ate his entire family and a rare monkey was eaten for lunch by hungry otters. The incidents happened at Bristol Zoo in December and were shortly followed by further tragedy when three rainbow lorikeets escaped."
An anonymous whistleblower claimed "the deaths and escapes were avoidable."
There are so few warty pigs in the wild that no one knows how many, or how few, there are. These pigs are native to the Visayan Islands in the central Philippines.