In October 1932, in Milwaukee's Washington Park Zoo, two young polar bears drowned a black bear in a pool, over the course of a half an hour. Hundreds of visitors gathered, as the group of animals that had been kept in a single enclosure—three grizzly bears, three polar bears, five black bears, and three wolves, in total—assembled to look on.
When the black bear finally died, the other animals began to eat its body. The staff of the Milwaukee Public Library, which recently recalled this failed experiment in multi-species housing on its blog Now@MPL, write that the zookeepers struggled to contain the melee; eventually, "the Fire Department arrived and removed the mutilated carcass with grappling hooks."
The Washington Park Zoo's keeper Edmund Heller got the idea to put all of these charismatic species in one enclosure from Heinrich Hagenbeck, son of Carl Hagenbeck, the German animal trainer, dealer, and zoo designer. One of the elder Hagenbeck's principles of zoo-building was that animals could be exhibited in uncovered pits or enclosures, rather than in the barred cells that had been common before that time. Heinrich Hagenbeck ran the family's zoo after his father died in 1914, and he experimented with combining species in a single enclosure, to "partially simulate nature," as the librarians write.
In Milwaukee, after the events of October 1932, Heller resisted the idea that he had made a mistake, and kept the group of animals together. In July 1933, a polar bear again drowned a black bear; Heller argued that the black bears would soon learn their lesson, and would stay away from the pool when polar bears were in the vicinity. But in August,1933, the polar bears trapped a third black bear in the pool and killed it.
These events were not common at the time—the librarians point out that newspapers nationwide reported on the drownings. Heller eventually relented, and the remaining black bears were moved to a separate enclosure.
After I posted the link to the library's blog post on Twitter, writer Eva Holland pointed out that this tragedy repeated itself in British Columbia in 2005, when two grizzly bears and a pack of wolves were temporarily housed together in a 5-acre enclosure at the wilderness sanctuary Grouse Mountain. In that case, one of the bears killed a grey wolf in a fight over food, as a group of visitors looked on.