The Hawaiian Islands have long been thought to support just one endemic land mammal in its brief geologic history, the Hawaiian hoary bat.
But research conducted by two scientists at Bishop Museum, and a third from the American Museum of Natural History, uncovered the presence of a second, very different species of bat.
Bishop Museum entomologist Francis Howarth was investigating lava tubes in Maui in 1981 when he discovered skeletal remains of the mysterious bat, now named Synemporion keana. Additional remains were subsequently found on four other islands: Hawaii, Kauai, Molokai, and Oahu.
Scientists believe this bat lived alongside the hoary bat for thousands of years before going extinct shortly after humans arrived on the islands.
“The initial specimens included skeletons embedded in crystals on the lava tube wall and thus were likely very old,” Howarth said. “(Late Bishop Museum mammologist Alan) 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 recognized that the small bat was very different from anything else he had seen and started the long process of investigating where it sits in the tree of life. He died in 2003 and the project was put on hold until Nancy Simmons, curator-in-charge of the American Museum of Natural History’s Department of Mammalogy, was brought in to continue the work.
“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,” said Simmons. “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.”
Scientists think that the extinction of Synemporion keana might have happened directly or indirectly because of human colonization of the islands and invasive, nonnative species that came with human explorers and settlers. “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.
Smaller than the hoary bat, Synemporion keana first appeared in the fossil record on the islands around 320,000 years ago and survived until at least 1,100 years ago, and possibly much later.
Synemporion keana, which is a kind of vesper, or evening bat, had an array of features that so far have made it impossible for the researchers to identify its closest relatives. Simmons and Howarth hope that future work with ancient DNA extracted from the fossils might help them solve the mystery.