Mound of 4300-year-old bat guano reveals the ancient history of Jamaica

0

Scientists have been drilling ice cores to analyze environmental changes for decades, but now the technique is applied to a less attractive medium: bat poo.

Researchers discovered a real mountain of guano deep in a cave in Jamaica, deposited over 4,300 years.

The stack has been largely untouched and is more than 1.8 meters high.

Analysis of undigested material in the manure sketches a timeline of everything from dry periods in the Middle Ages to the arrival of Christopher Columbus and the advent of the gas engine.

Researchers in Jamaica discovered a mountain of bat guano more than six feet high, deposited over 4,300 years.  Samples were manually removed using sterile scoops and trays

Researchers in Jamaica discovered a mountain of bat guano more than six feet high, deposited over 4,300 years. Samples were manually removed using sterile scoops and trays

“Bats play an important role in pollinating flowers, spreading seeds and controlling insect populations,” said researchers in a new study in the American Geophysical Union’s Journal of Geophysical Research: Biogeosciences.

‘It is therefore important that we understand how human activities and natural events change the feeding habits of bats, which can affect their ability to perform these important functions.’

About 5,000 bats of five different species currently use the Home Away from Home cave in Trelawny, Jamaica. as a shelter during the day.

The flying mammals have used the cave for over 4,300 years – sleeping, giving birth and, yes, defecating.

Researchers obtained a 'core' sample that stretched from the top of the dunghill to the oldest deposits.  They stopped about five feet down 'because the guano was so sticky that it became too difficult and time consuming to clean the tools'

Researchers obtained a ‘core’ sample that stretched from the top of the dunghill to the oldest deposits. They stopped about five feet down ‘because the guano was so sticky that it became too difficult and time consuming to clean the tools’

The Jamaican fruit-eating bat (pictured) is one of five species that nest in Jamaica's Home Away from Home Cave.  Analysis of different layers of poo revealed changes in the bats' diet over the millennia, pointing to periods of dry climate and the beginning of sugar cane production in the 16th century.

The Jamaican fruit-eating bat (pictured) is one of five species that nest in Jamaica’s Home Away from Home Cave. Analysis of different layers of poo revealed changes in the bats’ diet over the millennia, pointing to periods of dry climate and the beginning of sugar cane production in the 16th century.

The result is a pile of bat guano that is more than six feet high, deposited in successive layers for generations and is largely undisturbed.

“We study natural records and reconstruct natural histories, mainly from lake sediments,” said study co-author Jules Blais, an environmental scientist at the University of Ottawa.

“As far as we know, this is the first time that scientists have interpreted bat diets from the past.”

An intact pile of this size was a rare find, as guano was mined for centuries to make gunpowder and is still used today as fertilizer in much of the world.

But the steep drop at the mouth of the cave appears to have protected the pile from previously excavated.

Blais and his colleagues retrieved a vertical ‘core’ sample extending from the top of the stack to the oldest deposits for analysis.

They examined the samples for sterols, biological markers made by plant and animal cells that pass through the digestive system and are secreted largely intact.

Cholesterol, for example, is a sterol synthesized by animals.

The Antillean bat with ghost face (photo) also calls the cave home.  The scientists examined the bats' poo for sterols, biological markers made by plant and animal cells that pass through the digestive system and are excreted largely intact.

The Antillean bat with ghost face (photo) also calls the cave home. The scientists examined the bats’ poo for sterols, biological markers made by plant and animal cells that pass through the digestive system and are excreted largely intact.

A huge undisturbed pile of bat poo is a rare find: Guano was mined for centuries to make gunpowder and is still used today as fertilizer in much of the world.  Pictured: Home Away from Home Cave estuary

A huge undisturbed pile of bat poo is a rare find: Guano was mined for centuries to make gunpowder and is still used today as fertilizer in much of the world. Pictured: Home Away from Home Cave estuary

Determining which sterols were dominant in which guano layers was like opening a time capsule from a period of time: More recent samples recorded the chemical signatures of human activities such as nuclear testing and leaded gasoline combustion, the researchers said.

That, along with radiocarbon dating, allowed them to create a relative timeline for the different layers.

They also found changes in the carbon composition of the guano in the late 15th century, when Europeans arrived in Jamaica and sugarcane production began.

Looking deeper, they found that plant sterols increased with animal sterols in 1350 BC, at a time known as the Minoan Warm Period, and again from 900 to 1300 AD, during what is referred to as the Medieval Warm Period.

At the time, America’s climate would have been incredibly dry, and “we thought the bats preferred fruit food,” Blais said.

Study co-author Lauren Gallant, a graduate researcher studying under Blais, admitted the work had a certain “ ick factor, ” specifically collecting fresh guano from live bats in Belize to get a baseline.

A researcher descends to the guano drilling site.  Four-by-four-inch and four-inch pieces about one-third of an inch thick were carefully extracted and labeled

A researcher descends to the guano drilling site. Four-by-four-inch and four-inch pieces about one-third of an inch thick were carefully extracted and labeled

“The bats defecate in cloth bags and to collect the samples I had to search hundreds of bags,” she told the Daily Mail. “All night long, a pile of cloth bags gathered for me to search.”

The researchers manually removed the guano from the cave using sterile shovels to collect 10 cm thick pieces of manure that were about a third of an inch thick.

“The guano at the top of the core had a very high water content,” she added. “Normally, people just use a sterile scoop to weigh the samples for analysis, but because the samples were so wet, I had to use a pipette, similar to a pipette.”

They stopped about a meter and a half away, Gallant said, “because the guano was so sticky it became too difficult and time consuming to clean the tools.”

Their analysis suggests that guano can be used to collect ecological and environmental data when ice cores and soil sediment are not available.

“It also contains biological information that lakes do not have.” said Michael Bird, a geologist at James Cook University in Queensland, Australia, who was not involved in the study.

“There is a lot more work to be done and there are many more caves.”