YAKUSHIMA, Kagoshima Prefecture—Growing numbers of invasive raccoon dogs are preying on baby sea turtles on the beaches of Yakushima island, one of the world’s largest nesting sites for the theatened species.

Raccoon dogs not only attack turtle hatchlings that are trying to reach the safety of the sea, but they also use their front paws to dig up turtle nests and eat the eggs.

That makes raccoon dogs more potentially destructive to turtle populations than crows or cats, environmentalists said.

With little solid data on the scale of raccoon dog damage, local officials and the Environment Ministry’s Yakushima Ranger Office plan to gauge the raccoon dog population and implement measures to protect the sea turtles.

Raccoon dogs are not indigenous to Yakushima island, a World Natural Heritage site located about 60 kilometers from the southernmost part of Kyushu, one of Japan’s four main islands.

The animal is believed to have been brought to the island in the 1980s.

Since then, raccoon dogs have thrived and now likely inhabit all parts of the 505-square-kilometer island, according to ministry and local officials.

The animal has even been spotted in a mountainous area at an altitude of 1,600 meters, the Yakushima town government said.

The nesting season for sea turtles runs from around May to August. It takes on average two months for the eggs to hatch.

Evidence of raccoon dog attacks was found on Nagatahama beach in the island’s northwestern area. The beach is the largest nesting site in the North Pacific for endangered loggerhead turtles, and it also provides a nesting site for vulnerable green turtles.

Conservationists who inspected the beach in August said they found countless paw prints of raccoon dogs around destroyed turtle nests. Pieces of broken eggshells were scattered nearby.

They also watched footage from a security camera set up on the beach by Yakushima Umigame-kan (Yakushima sea turtle museum), a nonprofit group that works to protect sea turtles.

The footage showed a raccoon dog attacking a newly-emerged hatchling and also digging up the nest to prey on others.

Hirobumi Ueda, a representative director of the group, said reports about raccoon dogs’ assaults became more frequent from around 2010.

“Raccoon dogs apparently know when the eggs will hatch and come to the beach to target them,” Ueda said. “They go straight to the beach, ignoring baited traps.”

A ministry survey confirmed signs of animal predation at 20 to 50 turtle nesting sites annually on the island from 2014 to 2016.

Umigame-kan’s investigation found that the extent of damage last year was larger than many of the preceding years.

At one beach, about 100 of around 430 nesting sites where turtles had hatched showed signs of being attacked. At another beach, 70 to 80 percent of the nests were dug up.

Ueda’s group carries out nightly patrols and sets up nets to safeguard the nests.

But the nets cannot fend off all of the predators, given the vastness of the beaches and raccoon dogs’ ability to enter the nets through an opening, Ueda said.

“Raccoon dogs’ presence is a growing concern not only for hatchlings but also for the entire ecosystem on Yakushima,” he said.

Local officials say that deer and monkeys are the main culprits behind the damage to agricultural crops in Yakushima. But they suspect raccoon dogs are also responsible for some of the damage.

The Yakushima town government and the Yakushima Ranger Office plan to study the distribution of the raccoon dog population on the island and the impact on ecosystems. They will also look into ways to reduce the species’ numbers.

“It is not yet clear how much impact raccoon dogs have had on ecosystems, but we need to reduce their predation of sea turtles,” said Yasunori Takenaka, an officer with the Yakushima Ranger Office.

Toru Ikeda, professor emeritus of conservation ecology at Hokkaido University, warned that raccoon dogs could transmit the virus that causes Severe Fever with Thrombocytopenia Syndrome (SFTS), a potentially fatal, tick-borne disease.

Ikeda has been with Roundtable on Alien Species Control Inc., a Sapporo-based start-up affiliated with the university that has been involved in programs to control raccoon populations across Japan.

He urged more people in local communities on Yakushima island to join the effort.

“Raccoon dogs are detrimental to the island,” he said. “Islanders should not dismiss raccoon dog damage simply as a consequence of wildlife but should treat it as an alien species issue.”

Nagatahama beach was designated as a Ramsar Convention site in 2005 based on the recognition that it is an irreplaceable area for sea turtle conservation.