Making their routine rounds in the mountains of Amami-Oshima Island, which lies roughly halfway between Okinawa and Kyushu, Shintaro Abe and Masahiro Nishi are relieved every time they find evidence their hard work is paying off: rabbit droppings.
Abe, 49, is in charge of the Environment Ministry Naha Nature Conservation Office's mongoose eradication campaign, while Nishi, 41, is one of Abe's team of "mongoose busters." An increasing amount of droppings from the island's native Amami rabbits is a good indicator that the number of mongooses, their natural predator, has decreased.
Amami-Oshima is considered one of the world's biodiversity hot spots, given the large number of species peculiar to that area. The mongoose was brought to the semitropical island in the late 1970s to control the poisonous "habu" snake.
But with no natural enemy and a high reproduction rate, the mongoose population expanded rapidly and preyed on all sorts of native animals. This caused significant disruption to the natural habitat and much of the unique fauna on the island. The Amami rabbit, for instance, is threatened with extinction.
Abe and his mongoose busters have set up around 30,000 snares across the 72-sq.-km island. Placed at intervals of about 50 meters in targeted areas, the cylindrical plastic traps are specifically designed to catch and kill animals the size of a mongoose, which measure 30 to 40 cm long.
The team initially tried metal snares such as those for capturing weasels, but they also trapped precious species like Amami spiny rats and thus needed to be checked every day so the nontargeted animals could be released.
The team had to improve the design so creatures smaller than the mongoose could free themselves.
After graduating from a university in Tokyo with the goal of becoming a veterinarian, Abe moved to Amami-Oshima, following a former teacher who began a project there to breed monkeys for use in experiments.
At the same time, Abe was eager to be involved in studying living creatures and so began surveying the growing mongoose population with some friends in 1988.
To determine the mongoose distribution and its impact on the island, Abe collected witness reports and caught the animals in traps.
He also performed dissections to learn about their eating habits and reproductive status.
"I cried and kept saying 'I'm sorry, I'm sorry' during the first few times," Abe recalled. "I kept count up to the 3,000th mongoose and always wondered to myself, 'Hadn't I become a veterinarian to save lives instead?'"
Thanks to the expertise he gained, however, Abe landed the government job in 1999 and began a full-fledged mongoose eradication campaign the following year.
When the Invasive Alien Species Law took effect in 2005, Abe hired Nishi and 11 others as his mongoose busters. The specialist team has since expanded and now comprises 42 members along with three sniffer dogs.
The team's initial goal back in 2005 was to completely eradicate the mongoose in 10 years, but that proved unrealistic. Now the target is fiscal 2023.
Currently, about 200 mongooses are captured annually, down from the peak of more than 4,000. The estimated population on Amami-Oshima is down to around 300, about one-twentieth of what it once was.
"In the beginning, we used red meat as bait (in the traps), but it rots easily so we switched to using lard we pickled in salt," Nishi said.
The team also experiments with different flavors and in different forms, such as soaking cloth in noodle soup or making the soup into jelly blocks with agar, to discover what the mongooses like most.
Some of the captured ones are kept alive at the ministry's Amami Wildlife Conservation Center for use when experimenting with new traps and bait.
Teruyuki Niino, a mongoose handler at the center, acknowledged that "the selfishness of human beings" was behind the original problem and the need now is to eradicate the mongoose population, but "we can't let the island's endemic species become extinct."
As a result of the work of Abe and his team, the distribution of Amami rabbits has expanded and the island's ecosystem is recovering.
Unfortunately, the mongooses aren't the only problem.
"Stray dogs and cats are also enemies (of indigenous species)," Abe said. "Human beings' ignorance and greed are the reasons behind the increase in alien species and escaped pets. These animals have done no wrong, but we simply cannot let them live on."
