A study that could have implications for Hawaii’s timber and wind-turbine industries has found evidence of two distinct lineages of the endangered Hawaiian hoary bat, which flew 2,500 miles across open ocean in two migratory waves.
The study, published Wednesday in the journal PLOS ONE, involved researchers from Hawaii island and Michigan, and is the first to use genetic research to find evidence of two distinct types of endangered Hawaiian hoary bats.
Bat Migration
Two separate lineages of endangered Hawaiian hoary bats arrived in the islands in two waves 9,000 years apart, but it’s unclear why either variety made the three-day flight across the Pacific.
First wave of migration
10,000 years ago
Second wave of migration
800 years ago
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One type descended from an initial migration from the West Coast 10,000 years ago and later evolved in Hawaii with more red and brown fur and became 40 percent smaller than its cousins on the mainland. It’s found primarily on Hawaii island.
The second wave occurred just 800 years ago, and those hoary bat descendants spread across the islands and look more like their counterparts on the mainland in size, along with similar white, “frosty” fur, said Frank Bonaccorso, a wildlife biologist with the U.S. Geological Survey at Hawai‘i Volcanoes National Park who collected live bats and tissue samples and co-authored the study.
No one knows how many hoary bats of either variety remain in the islands because they live solitary existences and fly at night.
But Bonaccorso and lead author Amy Russell, associate professor of biology at Grand Valley State University outside of Grand Rapids, Mich., hope their study begins a new discussion about whether there should be state and federal protection for two different lineages of Hawaiian hoary bats, which is Hawaii’s state land mammal.
“If we identify them as possibly distinct populations within a species or a subspecies, it does have implications about how we manage the bat, how we manage the take of timber and has implications for the wind industry,” Bonaccorso said. “Bats do die from those two” industries.
The name of their study relies on scientific lingo while borrowing from Bay Area rocker Eddie Money. It’s called “Two Tickets to Paradise: Multiple Dispersal Events in the Founding of Hoary Bat Populations in Hawai‘i.”
A previous study by Bonaccorso found that hoary bats can pack on enough fat to fly thousands of miles in migratory routes around North America and could store enough fuel for the three-day trip from the West Cost to Hawaii, Bonaccorso said.
But exactly why the Hawaiian hoary bat left the continent for an archipelago in the middle of the Pacific Ocean remains unclear.
Hoary bats have been seen leaving land to fly out to islands off California. But nothing either 10,000 years ago or 800 years back offers theories why they would set off for the long, one-way trip to Hawaii, Russell said.
“There’s no evidence going back to those time points that made it especially beneficial for the bats to take out to the ocean,” she said. “They could have just gotten blown out by the wind.”
If so, Russell said it would have been easier for the ancient hoary bats to flap along with the tradewinds all the way to Hawaii, rather than fight a head wind back to the mainland.
“It wasn’t an unreasonable trip,” she said. “It was biologically possible.”
Bats have a sort of magnetic compass in their brains and can also navigate by landmarks, such as the peaks of various Hawaiian islands, Bonaccorso said.
“In science,” he said, “we look for the simplest explanation. By going with the wind, they were largely not draining themselves. And the wind took them to Hawaii.”
Both types of hoary bat were preceded by a third, smaller type of bat that likely arrived in Hawaii sometime during the Pleistocene Epoch, which included the last Ice Age.
The fossilized remains of that unknown species of bat have been found in lava tubes across the islands, Bonaccorso said, but genetic testing so far has produced little results to determine its origins.
New, more detailed genetic tests are also planned for the two modern-day varieties of Hawaiian hoary bats. And Bonaccorso hopes the results will lead to better management of distinctly different branches of an endangered species.
“This opens new discussions about what efforts we need to make to identify the boundaries of these two lineages more carefully,” he said.
