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Snapping-turtle expert in Chiba leads battle against invasive species

Growing population of invasive species poses a big threat to biodiversity

by

Staff Writer

Takeshi Imazu’s daily tasks are far from what a typical prefectural official handles.

For more than half of the week, he goes out to the Inbanuma marsh of Chiba Prefecture either to capture or study snapping turtles, a freshwater species that threatens local biodiversity.

Snapping turtles, considered one of the 100 most destructive invasive alien species by The Ecological Society of Japan, pose a major threat to the ecosystem and can cause serious injuries with their strong bite.

Imazu, 34, works at the Chiba Prefecture-run Chiba Biodiversity Center, and has dedicated his life to researching turtle ecology. He was hired by the prefecture in February as possibly the first-ever public servant in Japan tasked with developing new methods to capture and culling snapping turtles.

Although it’s been only about six months since he started working at the center, his contribution could go a long way, potentially leading to the extermination of the species in the country.

“I’ve always been researching turtles. I have experience in capturing snapping turtles, so I applied for the position to take advantage of that,” Imazu said during a recent interview with The Japan Times.

Hiring Imazu was the biggest step the prefecture has ever taken to exterminate snapping turtles, according to the Chiba Biodiversity Center.

In Chiba, snapping turtles were first seen in the wild in 1978. Since then, their population has exploded with few natural predators to keep its growth in check. With an estimated 16,000 snapping turtles now inhabiting the prefecture, the species threatens to destroy great swaths of local biodiversity — consuming native plants, fish and crustaceans.

The prefecture aims to cull over 2,500 snapping turtles annually. It started its extermination program in 2007, but the population kept growing. Finally, Imazu was hired to put an end to the problem.

Imazu said he is now trying out new capturing methods.

A new organization was recently contracted to be involved in the extermination program, and Imazu has spent a great portion of his time teaching its ranks how to use a conventional trap.

Imazu said he also wanted to test other tools, including fixed fishnets, but admitted that time is running out for this year.

Starting in mid-October, as water temperatures drop, snapping turtles will gradually go into hibernation, he said.

Meanwhile, he will continue using his own hands to dig mud to capture turtles, and release some of the animals with attached GPS tags to track their movements until spring, he said.

Before joining the institute, Imazu studied at the biology department of Toho University, and later earned his master’s degree from the Meiji University’s graduate school of agriculture.

While at Toho University, his graduation thesis focused on population characteristics and the ecology of Chinese pond turtles. He had specialized on the same type of turtle species in his research during graduate school.

The results of his research were published in the Bulletin of the Herpetological Society of Japan, and he has been involved in studies run by other groups such as the Japan Wildlife Research Center. However, carving out a career as a turtle researcher comes with many challenges, Imazu said.

“I’ve worked as an environmental consultant at several organizations, not as an official employee but as a part-timer or a temporary staffer,” he said.

Imazu’s previous job title: a pet shop clerk keeping tropical fish.

“I’ve always wanted to get a job where I could take advantage of my experience, but there were no such positions. Even a majority of the seniors at my university who studied turtles couldn’t find research positions. But this time, I was the perfect candidate for this job offer,” he said.

Imazu’s team at the biodiversity center has captured over 600 turtles since April.

Imazu, who also keeps 50 turtles at his home, said the extermination of invasive species of turtles is sad but unavoidable, noting that full blame for the problem can be laid at the feet of irresponsible pet owners who released the turtles into the wild.

Snapping turtles, which originally inhabited the Americas, were believed to have been introduced to Japan as pets in the 1960s.

The species can grow as heavy as 35 kg, with its shell measuring about 50 cm in length. As snapping turtles live for 40 years on average, with some living for up to 80 years, the animals can easily outlive the people who adopt them. After the novelty wore off and these exotic turtles grew unmanageable as house pets, some owners just threw them out into the wild to fend for themselves.

“In most cases, snapping turtles were released when their owners got tired of keeping them. It’s hard to believe that the situation has become this bad,” Imazu said.

Imazu’s contract term is three years. After that, he said he wants to continue pursuing a career that allows him to keep researching turtles and nothing else.

To date, snapping turtles have been found throughout Japan, with many even thought to be living in Ueno Park’s Shinobazu Pond and Nerima’s Hikarigaoka Park in Tokyo. Spotted in at least 20 prefectures, the turtles are overpowering domestic species of turtles and other vulnerable organisms, according to the National Institute for Environmental Studies database.

Chiba has high expectations for Imazu.

“It’s only been a half of the year, and I admit I have had my share of missteps. So I haven’t thought too deeply about my future career just yet,” Imazu said.

“But within the next three years, I’ll establish a new capturing method. After that, I will look for another job in which I can draw upon my experience.”

“Generational Change” is a series of interviews, profiling people in various fields who are taking a leading role in bringing about changes in society.