Animals in a Ugandan forest have been eating bat poo laden with viruses after tobacco farming wiped out their usual food source, a study has found.

A virus linked to Covid-19 was among the 27 identified in the poo eaten by chimpanzees, antelopes and monkeys.

Researchers say this finding sheds light on how new viruses might spread from wildlife to humans.

The animals were monitored in a study by the University of Stirling and the University of Wisconsin-Madison.

The six-year project was prompted when Dr Pawel Fedurek from the Faculty of Natural Sciences and Scotland's University of Stirling observed wild chimpanzees in Budongo forest eating accumulated bat excrement, known as guano, from the hollow of a tree.

In July 2017, he set up cameras which captured other species also eating the poo.

According to the peer-reviewed study, which features in the Nature journal, guano is an "alternative source of crucial minerals" for the animals after the the palm trees they once consumed were "harvested to extinction".

The trees were used by locals in Budongo to dry tobacco leaves, which were then sold to international companies.

For just over six months, researchers collected samples of guano from the tree hollow the animals were filmed eating from.

Lab analysis of the poo identified several viruses, including one related to SARS-CoV-2, the virus that caused the Covid-19 pandemic.

"It remains unknown whether the betacoronavirus found in the guano is transmissible to humans, but it does offer an example of how new infections might jump species barriers," a press release from the University of Stirling said.

"About a quarter the 27 viruses we identified were viruses of mammals - the rest were viruses of insects and other invertebrates," Prof Tony Goldberg, from the University of Wisconsin-Madison, in the US, told the BBC.

"All 27 viruses were new to science, so we don't know what effects they might have on humans or other animals. But one virus stood out because is was a relative of a virus everyone knows: SARS coronavirus 2."

Dr Pawel Fedurek, an expert in animal behaviour at the University of Stirling, said: "Our research illustrates how a subtle form of selective deforestation, ultimately driven by a global demand for tobacco, can expose wildlife and, by extension, humans to viruses residing in bat guano, increasing virus spillover risk.

"Studies like ours shed light on the triggers and pathways of both wildlife-to-wildlife and wildlife-to-human virus transmission, ultimately improving our abilities to prevent outbreaks and pandemics in the future."

The researchers hope their findings make it possible to intervene in the transmission of viruses between species and ultimately help to prevent future pandemics.