Yambaru was under siege.
The forested, mountainous northern region of the island of Okinawa, Japan, is home to several species found only on the island, including Okinawa rails. The rails’ dramatic coloring makes them easily recognizable—they have sleek, striped faces, white-barred breasts, and bronze backs accentuated by bright red-orange feet and beaks. Rails evolved to be nearly flightless, supported by a unique island ecosystem that had no carnivorous mammals—until humans stepped in.
In 1910, people hoping to protect themselves from poisonous Habu snakes set 17 mongooses loose on the southern part of the island with the intention that the small carnivores would eat the snakes. Unfortunately, the plan had a serious flaw: mongooses are active during the day, but Habu snakes are active at night. Instead of preying on snakes, the mongooses developed a taste for other local wildlife, including Okinawa rails.
Over the next century, the mongooses multiplied and expanded their territory northward. By 1980, it was clear that rail populations had rapidly declined in areas where mongooses had become established. By 2006, the estimated total population had diminished from around 1,800 to fewer than 1,000.
Researchers, wildlife managers, and government agencies in Japan recognized that eradicating mongooses from Yambaru was the key to preserving Okinawa rails. They also considered the benefits of cultivating a small insurance population in a local breeding facility in case the mongooses drove the wild population to complete extinction. They invited CPSG to help them organize their different but related conservation activities into a coordinated plan.
On the first day of the 2006 workshop, the participants split into two groups according to their expertise in order to focus on two main objectives. One group worked out the best ways to eradicate mongooses in Yambaru and support wild populations, and the other group, with input from the local and national zoo community, laid out plans to develop a healthy insurance population of Okinawa rails to ensure long-term species survival.
On the second day, CPSG brought the two groups together and created a timeline to show how, over time, the different elements of the plan could coincide and eventually achieve the overall aim of safeguarding rails in the wild. Establishing a common understanding of how major events were intertwined was crucial, since each group would depend on the other’s progress to succeed.
After the plan was forged, a new force entered the forest to help carry it out. The Yambaru Mongoose Busters, a group of professional invasive species managers and their highly trained mongoose-sniffing dogs, took to Yambaru daily to track, trap, and remove mongooses. By 2010, they had achieved the first target of the action plan—to secure a mongoose-free area in the northern part of the island, and by 2020, mongoose were eliminated from most areas north of the fence. Efforts to win the next battle—complete regional eradication of mongooses north of a mongoose-proof fence—continue tirelessly.
Concurrently, as recommended at the workshop, Japan’s Ministry of Environment created a policy for conservation-focused breeding of Okinawa rails. By 2012 a large, genetically healthy captive population was established, incorporating rescued birds that have been injured by cars and rehabilitated at the centers, as well as eggs that were abandoned by their parents after human activities, like mowing grasslands, disrupted their nests.
As of 2019, a captive population of about 80 birds thrives, with 45 birds released from captivity into mongoose-free habitat since 2014. And, a new national park, named Yambaru National Park in honor of the birds, protects the heart of Oknawa rail habitat.
Local conservation authorities estimate that the wild population of Okinawa rails has increased to around 1,500, thanks to decreased mongoose predation. The rails have been spotted in areas where they were once believed to have disappeared completely. By working with CPSG to organize their collaborative conservation efforts, stakeholders have given these living national monuments a second chance to thrive.
