4300 year old bat guano, anyone interested in using it in medicine. They are a rare treasure, at least for scientists, enough to understand the history of bat life and how the climate has changed over thousands of years.
The piles of guano are taller than a man (2 meters) and are divided into clear layers, like sedimentary layers in geology, recording history page by page.
By looking through this ancient book of dung, scientists figured out what the bats in the cave, for thousands of years, ate. The menu, in turn, provided clues to the climate and environment of the time – how changes in temperature and precipitation could affect species survival, and the kinds of insects and plants that bats could eat.
”We study natural archives and reconstruct natural history, largely based on lake sediments.” Jules Blais, a lacustrine scientist at the University of Ottawa in Canada, explains, “To our knowledge, this is the first time scientists have deciphered natural history through bat guano.”
The researchers are particularly interested in sterols, which are biochemical markers of diet produced by plant and animal cells. These sterols pass through the digestive system and can be preserved for thousands of years.
In addition, for comparison, they analyzed the guano of extant bats in the same area: Jamaica’s Home Away from Home Cave, which currently has about 5,000 bats of five different species. Their data gave the team a reference point for calibration.
The researchers found that there was a peak in plant sterols in the bats’ diet about a thousand years ago – corresponding to the Medieval Warm Period (900-1300 AD). It is thought that the Americas were particularly dry at that time.
Another peak in phytosterols was found around 1350 B.C., during what was known as the Minoan Warm Period. Drier conditions typically make life more difficult for insects, and during these periods, bats fed more on fruit.
”We infer from the results that past climate had an impact on bats.” Lauren Gallant, a biologist at the University of Ottawa, said, “Given the current changes in climate, we would like to see different ways in which bats interact with their environment.”
Another interesting finding is the change in the carbon composition of guano, which may be related to the initial landing of sugar cane in Jamaica in the 15th century. Chemical signals of human activity, such as nuclear testing and leaded gas molecules, can also be observed.
Bats are much more important to ecosystems than you may realize: they control insect populations, pollinate flowers, and disperse seeds. This cave method, which spans history and extends back thousands of years, is a non-invasive and effective way to study the diet and health of bats.
It is also notable that the same technique is applicable to other caves around the world and, the researchers say, may be particularly useful in areas without lakes and underlying sediments; it reveals much about climate change.
The study has been published in the Journal of Geophysical Research.
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