Bones in Lava Tubes Reveal Hawaii's Natural History

Bird bones from an extinct giant goose that once inhabited the big island of Hawaii are found in a lava tube. CREDIT: Matthew Cimitile

This Behind the Scenes article was provided to LiveScience in partnership with the National Science Foundation.

On a chilly, Michigan winter day, a day you dream about Hawaii, I was sitting in the office of Michigan State University zoology professor Peggy Ostrom. We were discussing ocean sequestration of carbon for a magazine article I was writing. After the interview, Ostrom mentioned her upcoming work on a project involving a Hawaiian endangered seabird, a collaboration with Smithsonian Institution scientists Helen James and Robert Fleischer.

She asked me to get back in touch with her in a couple months to discuss options for my participation. Not thinking much about it at the time, I told her I would. Little did I know this interview would begin an adventure to Hawaii, where I would document ongoing research on the endangered Hawaiian Petrel and go probing in lava tubes for extinct and endangered bird bones.

James has made a career of walking and crawling her way through lava tubes and sinkholes, identifying the biodiversity treasures Hawaii once held. From a large flightless goose to the Hawaiian `O`o, James and her colleagues have been putting together Hawaii's natural history with bird bones as the pieces. Altogether, they have identified around 40 extinct bird species, with more to come.

Uncovering extinct bird bones provides a historical record of Hawaii's natural environment. These bones tell us what was there before humans arrived 1,000-1,300 years ago and the changes that occurred. Knowing the composition of the natural Hawaiian environment can inform conservationists in how they manage and restore ecosystems.

More Going Extinct

This is timely and significant. Many native Hawaiian species, from plants to birds, are threatened or endangered of becoming extinct. If habitat modification and threats from invasive species continue, the stunning array of plants and animals in Hawaii will quickly disappear.

One bird of interest is the Hawaiian Petrel. A seabird that was said to have darkened the skies of Hawaii has declined considerably and continued loss of habitat and threats from introduced predators will further dim this petrel's chances of survival.

James, Ostrom and Fleischer are trying to uncover the size of the petrel population before human arrival and whether the petrel diet and feeding locations have changed over time. They are also asking whether declines in seabird populations affected Hawaiian plant communities by reducing the flow of nutrients from the ocean to the land.

My time in Hawaii was spent talking to experts, shooting photographs and attempting to film while meandering through lava tubes.

These geologic structures form when the outer part of a lava flow cools before the inner portion. What's left is a hollow tube of lava that can extend for hundreds of meters or more. Lava tubes are great locations to find bird bones. Many birds either fall into these formations or travel into the tubes, perhaps for protection from storms or other threats. Since light is minimal and many of the caves have steep entrances, birds may not find their way out.

Searching for bones

Hours were spent each day navigating the rough terrain of these caves, going up and down slope, concentrating on where to make our next step while simultaneously on the search for bones. At certain points the ceiling extended 12 feet above the jagged a'a (a rough form of lava rock) while at others it would drop to only three feet. Under low ceilings we would crouch on hands and knees to maneuver through the difficult terrain, making sure to keep our balance.

One of the lava tubes was in a native Hawaiian rainforest. Here, the cave was damp and wet, where water droplets seeped through the upper layer of dried lava and found their way to the back of your neck. Another tube was located in an unthinkable desert environment on the islands, where a couple cold drops of water on the back of the neck was a blessing. After spending six hours at a time in the cave, you learned to trust orange tracking tape to find your way out of a tube that could splinter off into three, four or five different directions.

When bones were found, the team would gather around the site to wait for James to have a view. After a glance, she would identify a giant goose or a flightless rail from the small pile of bones and then mark the site. Upon making our way out of the cave, we would safely store the bones in "bone boxes" to be shipped to the Smithsonian.

Left with hope

If we weren't on the search for bird bones, we were being educated by some of Hawaii's top scientists about research and conservation projects taking place on the islands. Many researchers are trying to answer basic questions about the nature of petrels, such as where they breed and how often they leave their nests during rearing of chicks. Others are finding effective ways to protect the native flora and fauna found nowhere else in the world.

While spending only a week in Hawaii, I observed the difficult ecological problems facing the state on many fronts. I left Hawaii not feeling angry or saddened, but hopeful. Hope from the many dedicated people who are taking part in discovering the natural history of the islands and preserving the biodiversity that remains. It's a hope that will be difficult to realize and will require more people becoming educated and involved in solving environmental problems.

But as one scientist wisely said, by knowing the past and what naturally occurred, we can manage and preserve the future, not just in Hawaii but throughout the planet.

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Editor's Note: This research was supported by the National Science Foundation (NSF), the federal agency charged with funding basic research and education across all fields of science and engineering. See the Behind the Scenes Archive.