Hawaiian hoary bats, or ‘ope’ape’a, may have migrated to the islands millennia ago by flying from San Francisco to the eastern part of Maui, the shortest possible flight distance between Hawaii and the Mainland, researchers report.

It’s impossible to know for sure exactly where the bats initially made landfall, but the 2,237 mile journey marks the longest overwater flight followed by the founding of a new population for any bat, according to a study published last week about the origins of the Hawaiian hoary bat.

The journey could have taken as few as three days, depending on wind conditions, according to Frank Bonaccorso, a wildlife biologist with the U.S. Geological Survey at Hawai’i Volcanoes National Park who co-authored the study.

The study also found that the Hawaiian hoary bat, which became the official state land mammal earlier this year, migrated to the islands from the Pacific coast of North America in two separate waves more than 9,000 years apart. Using DNA sampling and analytical tools, researchers determined the earlier migration occurred 10,000 years ago, while a more recent wave arrived in Hawaii about 800 years ago.

Descendants of both lineages are found on Maui and Oahu, but only descendants of the more recent migration are found on Hawaii island, the report said.

The fact that there are two evolutionarily distinct groups of Hawaiian hoary bats could help bolster protections for the endangered species.

“Because the Hawaiian hoary bat is the only living native land mammal in Hawaii and is on the U.S. Fish and Wildlife Service’s endangered species list, we want to know everything possible about its genetic history, relationships to other bats, and if there are unique subpopulations on different Hawaiian Islands,” said Amy Russell, associate professor of biology at Grand Valley State University in Michigan and lead author of the study.

No one knows how many hoary bats currently live in the islands because they live solitary existences and fly at night, Bonaccorso said. The bats have been spotted on the islands of Hawaii, Maui, Molokai, Oahu and Kauai but may only roost on Hawaii, Maui and Kauai, according to the U.S. Fish and Wildlife Service.

The bats can weigh from 0.49 to 0.63 ounces and have a wing span between 10 and 13 inches. Females are larger than males. Both eat insects. Their heavy fur coat is brown and gray and their ears are tinged with white, giving them a frosted or “hoary” look.

On Maui, the bats may be found in the Kahikinui Forest Reserve on the southern slopes of Haleakala, in forested sections Upcountry and other areas.

While long-distance overwater colonization might seem unlikely, it actually happened once before with another bat species that went extinct in the islands a few thousand years ago, researchers said.

The article, “Two Tickets to Paradise: Multiple Dispersal Events in the Founding of Hoary Bat Populations in Hawaii,” was published by the journal PLOS ONE and represented a joint effort between the University of Hawaii at Hilo, Grand Valley State University, Western Michigan University, EcoHealth Alliance and the U.S. Geological Survey.

* Eileen Chao can be reached at echao@mauinews.com.