Just how cute are giant pandas? The public can't get enough of them. The star attractions at Ueno Zoo in Tokyo are Ri Ri and Shin Shin, a male and female pair who helped attract some 4.4 million visitors last fiscal year — the highest number for 19 years.

Ueno Zoo certainly needs the money they generate. To host a pair of pandas, foreign zoos must pay the Chinese government at least $500,000 per year for 10 years. Rich countries such as Japan pay more like $1 million. However, the animals remain the "property" of China, which means that if something goes wrong — a panda dies unexpectedly, for example — the foreign zoo has a lot of explaining to do to the Chinese.

This happened in 2010, when Xing Xing, a 14-year-old male, died a grizzly death at Prince Zoo in Kobe City. The animal, also known as Kou Kou, was anesthetized by keepers preparing to collect sperm to use in artificial insemination. Unfortunately, Xing Xing vomited gastric fluid, breathed the acidic mixture into its lungs, and suffocated. Kobe City had to pay $500,000 compensation to China.