Based on a new five-year status review released earlier this year, the U.S. Fish and Wildlife Service is seeking to reclassify the ‘ōpe‘ape‘a or Hawaiian hoary bat from endangered to threatened.
The species was listed as endangered in 1970, “based on apparent habitat loss and limited knowledge of its distribution and life history requirements,” the review states.
Despite all of the research done in the decades since, largely spurred by the proliferation of wind farms throughout the state, the species’ population size and overall population trends are still mysteries.
However, a lot more is known about their distribution and life history: The bats breed on Kauaʻi, Oʻahu, and Hawaiʻi, and also likely breed on Maui and Molokaʻi. They’re also known to visit Kahoʻolawe and be present on Lanaʻi. A 2007-2011 study suggests the Hawaiʻi island population is stable or increasing.
Studies indicate there is geographic variation in the bats’ genetic structure, but it “does not clearly support taxonomic reclassification,” the review states.
Wind farms, as part of their habitat conservation plans, have contributed millions of dollars toward research to better understand the animals and help determine what actions are needed to offset the bat deaths caused by their turbines.
Last year, the state Endangered Species Recovery Committee held a two-day workshop where the results of the research funded by these wind farms was presented. The review incorporates much of that work.
“Overall, over the last eight years, ʻōpeʻapeʻa have been documented to occur over a much broader range than was known at the time of listing or when the species’ recovery plan was finalized,” the review states, also noting that the bats have been found to be highly mobile and to use fragmented habitats in a range of environments.
“While there are no monitoring methods that can quantify the abundance of ʻōpeʻapeʻa on each island, all of the major Hawaiian islands are now recognized as providing roosting, breeding, and/or foraging habitat for the species,” it continues.
With the last status review released a decade ago, the review identifies wind farms as a “new threat.” Eight are currently operating and one is under construction.
“Based on an 80 percent credibility standard used for modeling fatalities, the number of direct and indirect bat fatalities at all existing commercial wind projects on Maui are estimated to not exceed 11.3 bats per year,” the review states. On Oʻahu, that number is 14.7 bats per year; on Hawaiʻi island, it’s 3.2 bats per year.
Wind farms operating at night do pose a risk to bats on those islands, but not so much to populations on Kaua‘i, Lānaʻi, and Moloka’i, which don’t have wind farms. Although the bats are highly mobile, sometimes flying long distances in a single night, they generally do not move between islands, researchers have found.
“The entire statewide population of ʻōpeʻapeʻa are not at direct risk of extirpation from the limited operation of the wind farms on the islands of Oʻahu, Maui and Hawaiʻi, as not all individuals are likely to enter wind project sites and be killed,” the review states.
Still, it notes that wind turbines operating at night, which is when ʻōpeʻapeʻa are active, could cause a localized reduction in bat numbers if the facilities lie within the bats’ core use areas.
The extent of that reduction “depends on how rapidly a niche vacated by a fatality is filled, and on the behavior of the resident ʻōpeʻapeʻa population,” the review states.
Although the wind farms have been required to mitigate their take of the bats, through the conservation and management of forest lands, among other things, the effectiveness of those actions “remains uncertain and requires continued research, monitoring, feedback, and adaptive management to ensure the mitigation meets the success criteria and the needs of the bat,” it states.
Other “new” threats identified in the review include timber harvesting, coqui frogs, and climate change. Timber harvesting of trees taller than 15 feet, which occurs mainly on Kauaʻi and Hawaiʻi, is a threat to roosting bats and their dependent pups. Coqui frogs compete with the bats for food in low elevations, and climate change may foster the spread of those frogs to higher elevations, the review states.
“Warmer temperatures may allow an expansion of pupping habitat into higher-elevation areas, but may also affect habitat conditions by effecting changes to the prey base, resulting in suboptimal foraging conditions. These impacts may be mitigated by the ability of the ʻōpeʻapeʻa to range widely in search of resources and its generalist diet,” it adds.
Despite these and other threats, the FWS found that it now knows enough about the bats to recommend a change in their status.
Under the Endangered Species Act, the review concludes, an endangered species “is one which is in danger of extinction throughout all or a significant portion of its range. A threatened species is defined as any species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range. The ʻōpeʻapeʻa appears to possess resilience, redundancy, and representation across the islands such that it is not on the brink of extinction. Therefore, we conclude that the ʻōpeʻapeʻa appropriately meets the definition of threatened under the ESA.”
—Teresa Dawson
For Further Reading
- “Wind Farms to Fund ‘Research Push’ On Endangered Hawaiian Hoary Bats,” February 2017;
- “Draft Guidance Would Further Curb Number of Bats Wind Farms Can Kill,” and “New & Noteworthy: ‘Pretty Stable,’” April 2020;
- “Wind Farms’ Representatives Pick Apart Draft Guidance on Takes of Endangered Bats,” May 2020.
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