Bat guano from Missouri caves could offer climate change insight

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Anything that piles up over time can offer clues about past climate conditions or surrounding landscapes and how they’ve change, and that goes for bat poop.

Researchers from Missouri and Virginia are studying what’s scientifically known as guano that was taken from Missouri caves, the St. Louis Post-Dispatch reported recently. The study is being conducted by researchers from Washington University and the Missouri Botanical Garden, both in St. Louis, and from Virginia Tech.

“You definitely want to wear rubber boots,” said Christy Edwards, a conservation geneticist at the Missouri Botanical Garden. “You need to wear a mask. It’s pretty stinky. It’s dark. It’s not the most pleasant field environment.”

Edwards and colleagues see what could amount to centuries or millennia of localized natural history records buried within generations of bat diets.

“You’ve got insects flying around eating plants and then the bats flying around eating the insects,” said Rachel Reid of the geoscience department at Virginia Tech who began work on the project as a post-doctoral researcher at Washington University. So changes in the composition of the bat droppings can reflect how vegetation has transformed over time in the surrounding area.

In 2018, the team gathered guano from Mary Lawson Cave near Lebanon, Missouri. Sections can be analyzed for different carbon and nitrogen readings to identify changing trends over time. Modern guano samples from the cave’s population of gray bats were also gathered this past summer for comparison, using tarps placed in front of the entrance.

The analysis is continuing. One key question is how far back in time the guano record from that spot extends.

“Obviously the last couple hundred years would be reflecting shifts in agriculture and land-use changes,” said Edwards. “Over a longer period of time, you could get a look at climate.”

For example, different carbon signatures can reveal certain characteristics about the types of surrounding vegetation. Nitrogen readings can potentially reveal things such as the amount of precipitation in an area, Reid said. Brought together, the analysis can show how the land has changed over time, researchers say.

“We can explore not just the natural history, but how humans have changed landscapes,” said Reid.

Researchers say an improved understanding of paleoclimate offers plenty of important lessons for the present day.

“The better we understand what happened in the past, the better we can understand … how similar future events will affect species, as well,” said Edwards.