The Environment Ministry plans to basically ban the breeding or import of hybrids involving species designated as "invasive aliens," which authorities fear could heavily damage the nation's ecosystem, sources said.
So far, only invasive alien species have been subject to the ban. The rule change comes amid concerns that an increase in the number of such crossbred species, including Japanese monkey-rhesus macaque hybrids brought from other parts of Asia, will endanger a distinctive regional ecological system.
In Chiba Prefecture's Boso Peninsula, monkeys different from the domestic species were first discovered in the 1970s and later confirmed through genetic testing as rhesus macaques.
"We think privately raised rhesus macaques were released into the wild and reproduced," a Chiba Prefecture official said.
By revising an existing law, the ministry also plans to make it easier to exterminate the hybrids in mountain forests, even if owners of the land are unknown, the sources said.
Academic and educational breeding or import will be exempt from the ban.
If the law is revised as planned, individual offenders will face fines of up to ¥3 million or prison terms of up to three years and corporate offenders will face fines of up to ¥100 million.
Notification and consultation with landowners is currently required to exterminate alien organisms in mountain forests.
But since difficulties in locating landowners has prevented authorities from exterminating harmful invasive alien species, the ministry plans to simplify the procedures, making the process easier.
The upcoming law will also enable authorities to order owners of imported items to sterilize or dispose of them if invasive alien species such as ants and shells are detected in or on them during customs inspections.