The cats keep the rats under control in the monkey enclosure at Kunming Zoo, June 27, 2017. [Photo/VCG]

Two years ago, the zoo introduced two stray cats, but they proved unwelcome guests and were killed by the monkeys.

The zoo tried again, upping the number of cats to seven. Again the monkeys bullied their new roommates at the beginning, but, this time, the two sides gradually learnt to live peacefully together.

According to Wang, the monkeys even made room for their guests in one of the rooms set up for the monkeys, and they would pick flees from the cats during the day.