At first I thought it was really gross that people in South Korea were wiping out river rats for food. Then I found out that the rats are being sought for their bile. With bear bile in the short supply due to the overhunting of bears and new national protections, Koreans are turning to river rats as a source of ursodeoxycholic acid. Rats have an even greater amount of the acid than bears.
The rats were introduced in the 1980s and the South Korean government has been trying to eliminate the invasive species known as Nutria. Then a report came out on the higher level of the acid. The result was a sharp increase in people hunting the critters. That might all be for the good except for two problems. It is preserving this demand for bile in traditional medicine and the government now fears that people will start to actively breed Nutria and spread them throughout the country.
The government offers a cash reward of 20,000 won ($17; £14) for each Nutria caught, but people could likely make much more selling the bile.