Discovery of ‘invasive species gene’ prompts Japanese zoo to cull 57 monkeys
A city in Chiba Prefecture has culled 57 monkeys at a zoo after finding they were cross-breeds of Japanese monkeys and rhesus macaques, which have been designated as an invasive alien species in the country and apparently pose a threat to the natural environment.
Takagoyama Nature Zoo in Futtsu, Chiba, had considered the monkeys to be pure Japanese monkeys and had been housing them with 107 others. The culling, however, was conducted after the city found them to be crossbreeds.
The law on invasive alien species prohibits rearing of rhesus macaques and their mixed breeds.
The zoo is located only 3km from the habitat of Japanese monkeys, called “Nihonzaru” in Japanese and designated as a protected species in the country, prompting concerns about the impact on their habitat.
On the Boso Peninsula, where the zoo is located, rhesus macaques have bred after escaping from a now-defunct separate tourist facility. Having found some crossbreeds with Japanese monkeys, the city commissioned DNA checks to Kyoto University and a local research institute last autumn.
According to Futtsu city officials, Japanese monkeys are believed to have slipped in and out of the zoo through an opening in an old cage and crossbred with rhesus macaques.
Japanese monkeys live across the country, and their habitats in Aomori, Chiba, Osaka and three other prefectures, including the roughly 11 sq km area around the zoo, are designated as natural monuments.
“Cross-breeding was more rampant than we thought. We will update our facility and control plans so there won’t be a bad impact on wild Japanese monkeys,” one of the officials said.