New fossil findings show that Hawaii, long known to have painfully few mammals because of its long distance from any mainland, had a second land mammal for thousands of years. Until now, the Hawaiian hoary bat was thought to be the only endemic (native and restricted to one region) mammal living on land on the Hawaiian archipelago for all of its history.
The new bat is named Synemporion keana. Its remains were found in a lava tube more than 30 years ago - but scientists have worked on learning its place in the tree of life since then.
The unique flyer seems to have lived for thousands of years alongside the hoary bat. This newly known bat appeared in the islands' fossil record about 320,000 years ago. It was a surviving species until at least 1,100 years ago, or possibly a good deal later.
What's more, a research team believes that human colonization likely had a strong impact on the ancient bat, which became extinct not long after humans arrived on the islands. This might give us useful knowledge about how animals on islands are affected by humans and climate.
"It is most interesting that two species of bats lived together in the islands until about the time of colonization by humans," noted Nancy Simmons, a study co-author and curator-in-charge at the American Museum of Natural History's Department of Mammalogy. "Human activities, including altering the habitats for agriculture and bringing in exotic animals like rats - may have contributed to extinction of Synemporion.
"The Hawaiian Islands are a long way from anywhere, and as a result, they have a very unique fauna - its native animals apparently got there originally by flying or swimming. Besides the animals that humans have introduced to the islands, like rats and pigs, the only mammals that we've known to be native to Hawaii are a monk seal, which is primarily aquatic, and the hoary bat. So finding that there actually was a different bat - a second native land mammal for the islands - living there for such a long period of time was quite a surprise."
The new bat first turned up when study co-author Francis Howarth at the Bishop Museum in Honolulu found bat skeletal remains in a lava tube in Maui in 1981. Howarth, Alan Ziegler and other colleagues later found other bat remains on four other islands.
Ziegler, and later Simmons, investigated the bat's place in the tree of life. Synemporion keana was a kind of vesper, or evening bat. So far, many of its features have only distinguished it - scientists have not been able to identify possible relatives. The team hopes that working with the ancient DNA from the fossils will help them to glean more information.
"This extinct bat really is something new, not just a slight variation on a theme of a known genus," said Simmons. "The new bat contains a mosaic of features from taxa seen on many different continents. At some point, their ancestors flew to Hawaii, but we can't tell if they came from North America, Asia, or the Pacific Islands - they really could have come from anywhere based on what we know now."
Human colonization of the islands, and the arrival of non-native species following those people, may have contributed to the bat's extinction. "It seems possible that the reduction of native forests and associated insects after human colonization of the islands contributed not just to the extinction of plants, birds, and invertebrates, but also to the extinction of this endemic bat," said Howarth.
The finding was published in the journal American Museum Novitates.
Additional reporting by Catherine Arnold.
