Poop core records 4,300 years of bat diet and environment

An inaccessible cave preserved clues to Jamaica’s climate past in the sedimentary layers of bat guano


Research News


WASHINGTON–Deep in a Jamaican cave is a treasure trove of bat poop, deposited in sequential layers by generations of bats over 4,300 years.

Analogous to records of the past found in layers of lake mud and Antarctic ice, the guano pile is roughly the height of a tall man (2 meters), largely undisturbed, and holds information about changes in climate and how the bats’ food sources shifted over the millennia, according to a new study.

“We study natural archives and reconstruct natural histories, mostly from lake sediments. This is the first time scientists have interpreted past bat diets, to our knowledge,” said Jules Blais, a limnologist at the University of Ottawa and an author of the new study in the Journal of Geophysical Research: Biogeosciences, AGU’s journal for research on the interactions among biological, geological and chemical processes across Earth’s ecosystems.

Blais and his colleagues applied the same techniques used for lake sediments to a guano deposit found in Home Away from Home Cave, Jamaica, extracting a vertical “core” extending from the top of the pile to the oldest deposits at the bottom and taking it to the lab for biochemical analysis.

About 5,000 bats from five species currently use the cave as daytime shelter, according to the researchers.

“Like we see worldwide in lake sediments, the guano deposit was recording history in clear layers. It wasn’t all mixed up,” Blais said. “It’s a huge, continuous deposit, with radiocarbon dates going back 4,300 years in the oldest bottom layers.”

The new study looked at biochemical markers of diet called sterols, a family of sturdy chemicals made by plant and animal cells that are part of the food bats and other animals eat. Cholesterol, for example, is a well-known sterol made by animals. Plants make their own distinctive sterols. These sterol markers pass though the digestive system into excrement and can be preserved for thousands of years.

“As a piece of work showing what you can do with poo, this study breaks new ground,” said Michael Bird, a researcher in environmental change in the tropics at James Cook University in Queensland, Australia, who was not involved in the new study. “They really extended the toolkit that can be used on guano deposits around the world.”

Past climates, past diets

Like sediment and ice core records, the guano core extracted from the Jamaican cave recorded the chemical signatures of human activities like nuclear testing and leaded gasoline combustion, which, along with radiocarbon dating, helped the researchers to correlate the history seen in the guano with other events in Earth’s climate history.

Bats pollinate plants, suppress insects and spread seeds while foraging for food. Shifts in bat diet or species representation in response to climate can have reverberating effects on ecosystems and agricultural systems.

“We inferred from our results that past climate has had an effect on the bats. Given the current changes in climate, we expect to see changes in how bats interact with the environment,” said Lauren Gallant, a researcher at the University of Ottawa and an author of the new study. “That could have consequences for ecosystems.”

The new study compared the relative amounts of plant and animal sterols in the guano core moving back in time though the layers of guano to learn about how bat species as a group shifted their exploitation of different food sources in the past.

The research team, which included bat biologists and a local caving expert, also followed living bats in Belize, tracking their food consumption and elimination to gain a baseline for the kinds of sterols that pass through to the poop when bats dine on different food groups.

Plant sterols spiked compared to animal sterols about 1,000 years ago during the Medieval Warm Period (900-1,300 CE), the new study found, a time when cores of lakebed sediments in Central America suggest the climate in the Americas was unusually dry. A similar spike occurred 3,000 years ago, at a time known as the Minoan Warm Period (1350 BCE).

“Drier conditions tend to be bad for insects,” Blais said. “We surmised that fruit diets were favored during dry periods.”

The study also found changes in the carbon composition of the guano that likely reflect the arrival of sugarcane in Jamaica in the fifteenth century.

“It’s remarkable they can find biochemical markers that still contain information 4,000 years later,” Bird said. “In the tropics, everything breaks down fast.”

The approach demonstrated in the new study could be used to glean ecological information from guano deposits around the world, even those only a few hundred years old, Bird said.

“Quite often there are no lakes around, and the guano provides a good option for information about the past. It also contains biological information that lakes don’t.” Bird said. “There’s a lot more work to do and a lot more caves out there.”


AGU (http://www.agu.org) supports 130,000 enthusiasts to experts worldwide in Earth and space sciences. Through broad and inclusive partnerships, we advance discovery and solution science that accelerate knowledge and create solutions that are ethical, unbiased and respectful of communities and their values. Our programs include serving as a scholarly publisher, convening virtual and in-person events and providing career support. We live our values in everything we do, such as our net zero energy renovated building in Washington, D.C. and our Ethics and Equity Center, which fosters a diverse and inclusive geoscience community to ensure responsible conduct.

Notes for Journalists: This research study will be free available for 30 days. Download a PDF copy of the paper here. Neither the paper nor this press release is under embargo.

Paper title: “A 4,300 year history of dietary changes in a bat colony determined from a tropical guano deposit”


  • Lauren Gallant (University of Ottawa, Canada)
  • MB Fenton (University of Western Ontario, Canada)
  • Chris Grooms (Queens University, Canada)
  • Wieslaw Bogdanowicz (Museum and Institute of Zoology, Poland)
  • RS Stewart (Jamaican Caves Organization, Ewarton, Jamaica)
  • Elizabeth Clare (Queen Mary University of London, United Kingdom)
  • John Smol (Queens University, Canada)
  • Jules Blais, corresponding author (University of Ottawa, Canada)

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April 12, 2021 2:14 pm

I like the concept. But working with guano is a biohazard so I’m sure they’re taking precautions that are not necessary for mud or ice cores.

Reply to  Rah
April 12, 2021 3:14 pm

It looks like this is something like science – going out into the field and collecting hard evidence.
Interpretations of the findings, of course, can vary – as Rud Istvan notes below.


Trying to Play Nice
Reply to  auto
April 13, 2021 5:38 am

I find it hard to believe that nobody has ever studied bat guano like this before.

old engineer
Reply to  Trying to Play Nice
April 13, 2021 3:56 pm

And you would be correct.

I remember about 25 years going along a narrow path in one of the caves in the Carlsbad Caverns complex. The walls on each side of the path were a good 4 feet above my head. When got to an open space our National Park Ranger guide said “you just walked thru a bat guano deposit.

So a quick trip to google advanced search with “Bat guano” and “Carlsbad” as search terms, got me to a research paper dated 1980. See:


I am sure there are lots more.

old engineer
Reply to  old engineer
April 13, 2021 4:46 pm

I should have read on a further for this gem:

Using ratios in cave guano to assess past environmental changes
Daniel M. Cleary and Bogdan P. Onac
Geological Society, London, Special Publications, 507, 21 August 2020, https://doi.org/10.1144/SP507-2020-13

AbstractStable isotope ratios of cave bat guano reflect environmental influences at the soil and plant level within the foraging range of the bats. Carbon, nitrogen and hydrogen isotopes have utility in reconstructing precipitation and temperature as well as in tracing the influence of large-scale atmospheric circulation and climate variability. Guano-derived stable isotope time series have been demonstrated to effectively provide high-resolution records of palaeoenvironmental variation from the late Pleistocene to present. Owing to their influence on these isotopes, factors such as bat ecology, species foraging range and site location must be considered when interpreting such records. Research analysing the isotopic composition of guano has provided a highly resolved history of vegetation and climate dynamics previously less understood. In this chapter we discuss the factors influencing the δ13C, δ15N and δ2H values in guano and provide an up-to-date review of cave guano as palaeo-climate archive.

Apparently bat guano palaeo-climate studies are as common as lake sediment studies.

Researchers really should do a literature search before starting a research project.

April 12, 2021 2:25 pm

Plant sterols spiked compared to animal sterols about 1,000 years ago during the Medieval Warm Period (900-1,300 CE), the new study found, a time when cores of lakebed sediments in Central America suggest the climate in the Americas was unusually dry. A similar spike occurred 3,000 years ago, at a time known as the Minoan Warm Period (1350 BCE).”

…. thereby proving that Michael Mann is bat sh!t crazy ??

Reply to  philincalifornia
April 12, 2021 2:39 pm

… but much more efficient. Mann could have analyzed a single bat turd to put together a similar report.

Reply to  DonM
April 12, 2021 5:54 pm

Oh no he wouldn’t.

His report would totally erase the Medieval Warm Period and the Minoan Warm Period. He would prove conclusively that the Earth’s climate has been absolutely unchanging until we started warming it up by putting more CO2 into the atmosphere.

As always, I gleefully point out that, by avoiding the production of evidence under his control in the Ball case, Mann has, by adverse inference, confessed that he does belong in state pen rather than Penn State.

oeman 50
Reply to  DonM
April 13, 2021 7:33 am

And the bat turd would be upside down.

April 12, 2021 2:27 pm

Bat Guano Expert. Hmmm, there’s a job my high school guidance counsellor never mentioned. Sheeesh.


Reply to  Bob Tisdale
April 12, 2021 8:11 pm

Never too late to learn something new Bob, just think, with an Honorable Doctorate in Bat Guano you would be doubly qualified to argue Climate with the likes of the Possum Dr Flannery but you would have more ammunition since you would be highly qualified with guano!!

Reply to  Bob Tisdale
April 13, 2021 2:06 am

One of the characters in Stanley Kubrick’s masterpiece Dr Strangelove is named “Colonel Bat Guano”.

Joe Wagner
April 12, 2021 2:32 pm

Ok- its going to happen: let the jokes flow!

While I can see the merits in this, trying to get consistent results from such an area strikes me as being bat-guano crazy.

Rud Istvan
April 12, 2021 2:56 pm

This is silly. The study says this cave currently hosts 5 different bat species, illustrated was the Jamaican fruit bat. Simple changes in population mix (insect eaters to fruit eaters) having nothing to do with background climate but everything to do with, for example, disease (horror, bat coronaviruses) could also explain the results. And last I checked, Jamaica was sitting in a rather wet year round eastern Caribbean Sea, not sometimes dry Central America (think decline of the Yucatan Maya 1000 years ago likely due to drought).

Rud Istvan
Reply to  Rud Istvan
April 12, 2021 3:10 pm

Did some quick further research. Turns out that with recent advances in ‘semiautomated’ analytic chemistry, environmental sterols in lakes, ponds, and soils have become a very trendy environmental research area. Now it has reached climate change via bat shit.

Joel O'Bryan
Reply to  Rud Istvan
April 12, 2021 5:18 pm

Sounds like a perfect fit for Mike Mann’s expertise.

Reply to  Rud Istvan
April 13, 2021 8:57 am

Reviewers determined that the bat guano studies were crap….

April 12, 2021 2:57 pm

Guano “holds information about changes in climate”

That info is only as good as the assumptions made as to how it correlates to the food sources and how well the food sources correlate to the climate. May be yet another specious proxy in a never-ending search for proxies.

April 12, 2021 3:13 pm

“sterol markers pass though the digestive system into excrement and can be preserved for thousands of years.”
Bats are responsible for microplastic hydrocarbon compounds that do not break down over millenia!

“We surmised that fruit diets were favored during dry periods.”
As if dry weather is bad for insects didn’t mean that dry periods were also bad for fruit?

A lot of unsupported guesswork amounts to bull — not bat — crap, no matter how well written, or where it is published.

Reply to  dk_
April 12, 2021 4:50 pm

I read, never comment. Not in the habit of doing so. But as a historian and archaeologist, I must say I am stunned … “the arrival of sugarcane in Jamaica in the fifteenth (sic) century” (i.e. in the 1400s CE)? Really? Thus, well before 1492 (“in the fifteenth century”)? I.e. Saccharum officinarum, S. sinensis and S. barberi? Please!!!!!!! EurekAlert really needs to improve its ‘fact-checking’.

Jeff Alberts
Reply to  MElbl
April 12, 2021 6:05 pm

Isn’t 1492 in the 1400s?

Reply to  Jeff Alberts
April 12, 2021 6:32 pm


Thank you for the question. I was merely trying to set the record straight, and it was not my intention to be hypercritical or anything of the sort. Neither am I trying to play semantics. The article, as such, explicitly claims that there was sugarcane in Jamaice “in the 1400s CE” (specifically). NO post-contact records of any sort suport this, and I would genuinely love to see conclusive field archaeology data corroborating the claim that pre-1501 / 1508 (pre-contact) Taino in Jamaica knew and cultivated the sugarcane on a significant scale. Yes, I do read Spanish and Portuguese (and Latin) fifteenth and sixteenth-century sources and colonial records fluently, in the manuscript original, and I do not require printed versions or translations, even though I have worked with most of such. I am familiar with the vast majority of the relevant sources. I am not trying to posture or impress. Very simply, if part of the article’s chronology is, perhaps, predicated on the claim that sugarcane was indeed present in environmentally significant quantities in the island in the 1400s CE (i.e. pre-contact) (as explicitly stated in the article), then the connected chronology and analysis is basically off by 50 years to a century where the relevant 1400-1500s section of the data is concerned.

Zig Zag Wanderer
Reply to  MElbl
April 12, 2021 8:17 pm

I wonder if it’s just a comprehension error, labelling the 1500s as the “fifteenth century”? It’s a common mistake.

Rich Davis
Reply to  Zig Zag Wanderer
April 13, 2021 6:10 pm

It is EurekAlert! after all.

Clyde Spencer
Reply to  Jeff Alberts
April 12, 2021 6:33 pm

According to Wiki’ the Portuguese introduced sugar cane to the Caribbean in 1550, and it was important from the 18th through the 20th centuries.


Pat from kerbob
Reply to  Clyde Spencer
April 12, 2021 6:49 pm

It was so important that the French figured those small islands were worth more than all of canada

Reply to  Pat from kerbob
April 12, 2021 10:47 pm

Sacreblue! They didn’t know or forgot about maple syrup! I fart in their general direction!

Trying to Play Nice
Reply to  Pat from kerbob
April 14, 2021 4:52 am

And Trudeau is trying to prove them correct.

Last edited 1 year ago by Trying to Play Nice
Pat from Kerbob
April 12, 2021 3:13 pm

So, what i read from this is that they just confirmed that the MWP period and the Minoan warm period were not isolated to europe like the climate scientologists always like to say.

Do they know they will lose future funding opportunities?

April 12, 2021 3:34 pm

Great detective work. Sedimentary my dear Watts.

April 12, 2021 3:40 pm

“As a piece of work showing what you can do with poo, this study breaks new ground”

Well, maybe. But packrat (Neotoma spp.) middens composed of dried rat urine, feces, and other debris have been used to assess paleo climate back to 50,000 years.

April 12, 2021 4:27 pm

At least it’s not another pile of shit from James Cook University !!!

Joel O'Bryan
April 12, 2021 5:20 pm

Using a climate tie is just a way for researchers across diverse fields to ride the grant gravy train and virtue signal the same time.

Tom in Florida
April 12, 2021 5:25 pm

Perhaps we shouldn’t be so quick to poo poo this story.

April 12, 2021 5:25 pm

I kind of doubt the arrival of “sugarcane in Jamaica in the fifteenth century” what with Columbus sailing the ocean blue in 1492. Likely it was the 16th century.

April 12, 2021 6:14 pm

I wonder what the resolution of the proxy is? It would be pretty low, given that each year would be less than 0.5mm of poop. Then you would need to account for a “mixed layer” caused by the various species of beetles and other invertebrates that would live in the top few centimetres of the pile. Though, the thickness of the layers would be compressed as you went down, so the top mixed layer would represent less time than a naive layer distribution would presume.

Zig Zag Wanderer
April 12, 2021 8:11 pm

As a piece of work showing what you can do with poo, this study breaks new ground

I dunno. Climate Scientologists have been pretty successful at this for decades…

Peta of Newark
April 12, 2021 9:23 pm

What gets me about these things almost all thinking about ‘change’ is that:
Climate controls Everything

What if, it was or is the other way round.
What if Everything controls Climate
What if something really small, modest and massively overlooked actually: Controls Climate?

We’re told, “The diet of the bats changed

Is it beyond the bounds that ‘a particular’ species of plant, favoured by the bats ‘started to run out of its food or essential nutrient’
It would then be prone to disease, pest attack and fire, would go into decline but then, be replaced by another species with a different set of limiting nutrients.
And Stereos as a consequence.
Ain’t that is the whole theory and practice of Crop Rotation inside agriculture and has been for as long as agriculture has been practised.
Easily twice as long as the record here

Or what if the existing plants were given a huge dousing of fertiliser. What if a nearby volcano ‘smothered’ them with dust.
Or sulphur loaded rain?
The original weaker ones would in fact be smothered but once the dust had washed off into the soil, a whole new generation and species mix would set off ‘with vigour’

Isn’t that what happened with the dinosaur extinction 65 million years ago. So lets imagine something smaller and more local. There is after all a volcano going off in that part of the world right now.

Underwater volcanoes and assorted rumblings would produce tsunamis.
(Would that explain the Bermuda Triangle – an epic burp/belch/outgassing of CO2 and whatever gases directly under a hapless ship and perfectly losing its buoyancy in the fizzy water)

What about a huge flood of water washing over the place, clearing away the tired old soil, exposing some fresh new soil/rock/dirt and a new species mix of plants setting off from that event. No need for A God to Change the Climate.
Cosmic Rays can stay at home, as can The Emperor’s underpants, fabricated from pure Carbon Dioxide as they are.
Bit like Star Wars innit, can’t you picture A God (some random baddie) pointing his/her arm and cosmic rays come fizzing out of their finger-tips. Right at ya!!!!
Or, and ever so sweetly, blowing you a ‘poisoned kiss’
Isn’t that exactly CO2?
Something nice & good being hideously twisted out of all recognition by warped & dysfunctional science, minds and thinking.
(haha Explains a lot don’t it. We’ve seen it all this before, at the movies)

So what have we actually got here?
They keep pointing to the symptoms but never to any actual cause of those symptoms. All so perfectly circular, symptoms cause symptoms. For truly simple-minded types, yes.
But symptoms are symptoms – they don’t cause themselves.
(Why am I minded so very strongly of Covid right now? Also the insane circus surrounding it)
Aren’t we supposed to have moved on from an assortment of Gods that ‘did stuff’?
Have we regressed to the Dark Ages?

To these folks any of those things, soil erosion, volcano, tsunami would look like ‘Climate Change’ but weren’t.
Simply Old Ma Nature doing a bit of gardening – throwing old the old ‘poor doers’ and bringing in some fresh blood.
Yes, The Climate would have changed because the plants are effectively in control.
They do it via water – which these muppets actually do know, without knowing it.
(The bit where they rattle on about dry spells, insects and fruits)

No need for an invisible and all powerful magic hand to bring on Natural Variation
The plants did it. Gaia did it.

Oh noes, I said it. ‘Gaia’
What ya gonna do about it, burn me at the stake………..
(Do recall, the word witch translates as ‘Wise One’ ## I get the last laugh)
Plenty would wouldn’t they?
UK Plod at the request of Princess Nuts-Nuts would ‘do the biz’
After having been ‘anonymously’ tipped off by (supposed) friends and neighbours – just like those Polish Jews who went to their church, in London, on Good Friday
yes, the 1930’s were ‘a bit dark’

## Nicely explains what happened to Mr Trump innit – a Wise One who got burned at the stake.
Yes. That’s it. We really are in a Dark Age

Last edited 1 year ago by Peta of Newark
Patrick healy
Reply to  Peta of Newark
April 12, 2021 11:43 pm

Wonderful perambulation through the weed infested scientific field Peta.
Any advance on the Wuhan Bat theory?

April 12, 2021 9:52 pm

At only 1/2 a millimeter of bat-poo per year, you are only going to determine chemistry change trends over a span of probably 20 mm, so maybe a 50 year change in bat diet might become apparent. So a long ways from tree rings.

April 12, 2021 10:40 pm

+10 for mentioning the Medieval and Minoan Warm Periods!

Bruce Cobb
April 13, 2021 4:57 am

Must. Not. Make. Poopjokes, ok here’s one:
What did one poop core say to the other?
“So tired of your crap!”

Reply to  Bruce Cobb
April 13, 2021 9:06 am

That one stunk. 🙂

High Treason
April 13, 2021 5:01 am

Deep in to the future, human poo cores will be analysed. They will find our diet today consisted of swallowing huge amounts of bovine excrement. Initially, the researchers could be forgiven for thinking humans either evolved in to dung beetles or were taken over by the dung beetles in some titanic battle.

Right-Handed Shark
April 13, 2021 6:43 am

They certainly know they’re shit. And no, I didn’t mean “their”..

April 13, 2021 7:07 am

Not enough feces jokes in the comments section.

Reply to  leowaj
April 14, 2021 2:58 pm

“Where there’s muck there’s brass”

April 13, 2021 12:08 pm

OK, Someone has to say it “Holy batshit Batman- Robin

old engineer
April 13, 2021 4:04 pm

Just another use of an old division of biology- Scatology.


In medicine and biology, scatology or coprology is the study of feces. Scatological studies allow one to determine a wide range of biological information about a creature, including its diet, health and diseases such as tapeworms. Wikipedia

April 14, 2021 2:56 pm

Refractory plant substances can indeed be very good climate proxy material. This was shown in the classic study by Jessica Tierney et al in 2017, who reconstructed climate in north east Africa in the last 200,000 years in the context of study of early human migrations from Africa. They analysed leaf waxes deposited in marine sediments after being blown offshore from the Horn of Africa. This provided accurate reconstruction of humid and dry periods over this interval.


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