A Japanese zoo has culled 57 primates officials thought were Snow Monkeys because they carried the genes of an "invasive alien species".

The possession and transport of the Rhesus Macaque is banned under Japanese law, but somehow their DNA get into the mix at the Takagoyama Wildlife Zoo on the Boso Peninsula in Chiba Prefecture.  Culling of the non-native form of macaque is allowed under the law to protect the indigenous species.  Snow monkeys are a large part of Japanese life and culture, and are one of the country's major tourist attractions.  And in this case, officials were concerned the mixed-breed monkeys might escape and interbreed with the distinctive, red-faced population.

An official with the Chiba prefectural government said, "They have to be killed to protect the indigenous environment"; and Junkichi Mima of the conservation group WWF Japan agreed, noting that invasive species cause problems "because they get mixed in with indigenous animals and threaten the natural environment and ecosystem".

"Preventing exposures to foreign animals is very important," said Tomoko Shimura of the Nature Conservation Society of Japan.

No one actually felt very good about euthanizing the 57 monkeys, a process that took about a month.  After the task was completed, the zoo operator held a memorial service for the monkeys at a nearby Buddhist temple to appease their souls.