Correction: A previous version of this story incorrectly stated that the Fish and Wildlife Service had announced a proposal to downlist the Hawaiian hoary bat’s status to threatened, but the agency has so far announced only its intent to propose a status change for the species.

When the furry, rodent-sized Hawaiian hoary bat was declared an endangered species in 1970, little was known about where in the islands it dwelled or what the species required to survive.

The nocturnal night-flyer leaves its roost in the trees only after dark to consume 40% of its body weight in bugs, making its whereabouts difficult to map and its population difficult to count.

But thanks to millions of dollars of recent research funded by the wind farms that threaten the species, scientists now know that the solitary, highly mobile bat roosts, breeds and forages on all of the major Hawaiian islands. It’s also known to visit Lanai and Kahoolawe. A four-year study completed in 2011 suggests that the Big Island population is stable or growing.

It is unknown how many endangered Hawaiian hoary bats are left in the islands. Forest and Kim Starr

Although new research has revealed that the bats are more widely distributed across the island chain than previously believed, it remains a mystery how many of these jeopardized animals exist.

Scientists still don’t have enough information about the species to estimate its population size.

Despite glaring gaps in scientists’ understanding, Environment Hawaii first reported on Nov. 1 that federal regulators are preparing a proposal to strip the imperiled, uniquely Hawaiian creature of its endangered species status.

The U.S. Fish and Wildlife Service said the animal, also known as the opeapea, no longer appears to be on the brink of extinction and therefore should be reclassified as a threatened species.

The agency said its decision to develop a proposal to downlist the species is based on a five-year status review published in March that suggests the species is resilient, living on more islands than previously thought.

The bats would still be protected under the Endangered Species Act as a threatened species. But some conservation groups have expressed concern about reducing the bat’s protective status when scientists still have so much to learn.

“The real question is will they be protected to the level that they need in order to survive and recover as a threatened species?” said Maxx Phillips, Hawaii Director for the Center for Biological Diversity. “And I just don’t agree. I believe that the best available science shows that these species need the highest level of protection.”

Designated the state’s official land mammal — and the only land mammal native to Hawaii — as Environment Hawaii first noted, the Hawaiian hoary bat is under attack from timber harvesting that threatens the homes of adult bats and their dependent pups and coqui frogs that compete with the bats for food.

Wind farms operating at night, when the animal is most active, can lead to collisions that kill an average of 15 bats per year on Oahu, about 11 on Maui and three on the Big Island, according to the five-year status update.

There are eight wind farms operating across the state and one is under construction.

Research funded by the wind farms that threaten the Hawaiian hoary bat has revealed that the bat exists on more islands than previously thought. Jack Jeffrey

The Center for Biological Diversity said it supports the development of wind energy projects, which contribute to Hawaii’s goal of operating on 100% clean energy by 2045. But Phillips said Hawaii’s wind farms still have changes to make so that they’re operating in a way that minimizes negative impacts to endangered and threatened native species.

“We haven’t seen that happen with our wind farms yet,” she said.

So far, nearly all of the money that Hawaii wind farm developers have invested in mitigation measures, as part of their habitat conservation plans, has funded research, Phillips said.

“While it’s great to be able to learn more about the opeapea, it doesn’t mean that research is offsetting … the amount of bats that they’ve killed,” she said. “So it seems at this point that this decision by the Fish and Wildlife Service is definitely premature and counter to the best available science.”

One effective technique to reduce bat deaths, Phillips said, calls for wind farm developers to lock the turbine blades to stop them from spinning at night when wind speeds are low enough to permit the Hawaiian hoary bat to take to the sky. When wind speeds rise, the bats, which weigh as much as a mouse, can’t fly.

This technique, called wind speed curtailment, is something that wind developers have started to implement in Hawaii, Phillips said.

Another method that Kawailoa Wind Farm on Oahu has found promising, according to Phillips, is called acoustic deterrence, which involves emitting a noise that encourages bats to move away from the turbines.

But Phillips said researchers haven’t yet identified mitigation techniques that the wind farms can take to offset the bat deaths that still do occur.

And since the burden is on the violator of the Endangered Species Act to propose mitigation measures, Phillips said more work needs to be done to define these actions.

In the case of threatened and endangered seabirds that are prone to fall out of the sky after encountering bright artificial lighting, mitigation efforts might call for the violator to fence in a known seabird nesting colony to help protect the seabirds from predators.

There’s no equivalent mitigation measure for the Hawaiian hoary bat, Phillips said.

“We just don’t have that type of reliable information as it relates to the opeapea,” she said. “So none of the projects have been able to actually mitigate the (bat deaths) that they caused.”

The Hawaiian hoary bat first arrived in Hawaii 10,000 years ago after making an unlikely 2,500-mile journey from its North American origins.

The cryptic bat, with its foot-long wings, has evaded researchers for years due to its tiny size, its nocturnal, solitary nature and its ability to fly long distances in a single night.

The bats roost in tall treetops and female bats give birth once a year, usually to twins.

In 2015, the bat joined the Kamehameha butterfly, nene goose, humpback whale, humuhumunukunukuapuaa and Hawaiian monk seal in the exclusive club of official state animals. The goal of the designation was to raise public awareness of the threatened species.

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