The Hawaiian Islands have been known as a place with only one endemic (native, restricted to one region or area) land mammal, in all the brief geologic history of this archipelago. That mammal is the Hawaiian hoary bat.
Now new fossil findings say that another and very different type of bat lived along with the hoary bat for thousands of years. It went extinct a short time after humans' arrival on the islands, says the new research.
The new bat is called Synemporion keana. Its remains were first found in a lava tube more than 30 years ago. Scientists have been threshing out its place in the tree of life since then.
"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," noted Nancy Simmons, a paper co-author and curator-in-charge at the American Museum of Natural History's Department of Mammalogy. "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 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.
"The initial specimens included skeletons embedded in crystals on the lava tube wall and thus were likely very old," said Howarth. "Ziegler eagerly guided me through the bat collection at the Bishop Museum to identify the bat and show me features to look for in order to find additional material for study."
Ziegler, and later Simmons, investigated the bat's place in the tree of life. The new extinct species 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. Synemporion keana was a kind of vesper, or evening bat. So far, many of its features have 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 .
