You may not throw away a pile of 4,300-year-old bat poop for a second look – but for a group of scientists, it provided an interesting perspective on how bat diets and therefore climate conditions they have changed over thousands of years.
Taller than the average person (2 meters or 6 and a half meters), the pile of poop (also known as guano) records history in clear layers, like the sediments under a lake.
By analyzing the layers back in time, scientists have been able to figure out changes in the diets of bats that have lived in this cave for millennia.
In turn, dietary changes provide clues as to what the climate and environment may have been like at that time, with temperature and precipitation variations affecting animal life and the types of insects and plants available to bats.
“We study natural archives and reconstruct natural histories, mostly from lake sediments,” says limnologist Jules Blais of the University of Ottawa in Canada. “This is the first time scientists have interpreted bat diets in the past to our knowledge.”
Thin slices of bat guano core. (Chris Grooms)
The researchers were particularly interested in sterols, biochemical markers of the diet produced by plant and animal cells. These sterols pass through the digestive system and can be stored for thousands of years – as was the case here.
An analysis was also made of poop from bats currently living in the same location: Jamaica’s Home Away from Home Cave, which currently houses about 5,000 bats from five different species. This gave the team a baseline against which to work.
Researchers have found that there is an increase in plant sterols in the bat diet about a thousand years ago, which corresponds to the warm medieval period (900-1,300 CE), when America was thought to be particularly dry.
Another peak of plant sterol was found around 1350 BC, at a time known as the Minoan Warm Period. Drier conditions usually make life more difficult for insects, and in these times bats tasted fruit more often.
“We deduced from our results that the past climate had an effect on bats,” says biologist Lauren Gallant of the University of Ottawa. “Given current climate change, we expect to see changes in the way bats interact with the environment. This could have consequences for ecosystems.”
Another interesting discovery was the changes in the carbon composition of guan, which probably correlated with the arrival of sugar cane in Jamaica in the 15th century. Chemical signs of human activities, such as nuclear testing and the arrival of lead gas, could also be observed.
Bats are more important to ecosystems than you might think: they control insect populations, pollinate flowers and disperse seeds. This cave method is a non-invasive, effective way to study your diets and check your well-being throughout a history that – with the right bunch of guano – can stretch back thousands of years.
It is also worth noting that the same techniques used here can be applied to other caves around the world, say researchers – which could be especially useful in areas without lakes and underlying sediments, which reveal a lot of the same information about the climate. time.
“As a work that shows what you can do with poo, this study opens a new path,” says geologist Michael Bird of James Cook University in Australia, who was not involved in the new study.
“They have really expanded the set of tools that can be used on guano depots around the world.”
The research was published in Journal of Geophysical Research: Biogeosciences.