The most common bat in the United States, the big brown bat boasts an unusually long lifespan of up to 19 years. A new study led by researchers at the University of Maryland has revealed one of the secrets to this bat’s exceptional longevity: hibernation.
“Hibernation allows bats, and presumably other animals, to remain in northern or very southern areas where there is no food during the winter,” said the study’s senior author, UMD biology professor Gerald Wilkinson. “Hibernators tend to live much longer than migrants. We knew that, but we didn’t know if we would detect changes in epigenetic age due to hibernation.”
The researchers determined that hibernation for one winter extended the big brown bat’s epigenetic clock — a biological marker of aging — by three quarters of a year. A study published in the journal Proceedings of the Royal Society BAugust 10, 2022 also included scientists from McMaster University and the University of Waterloo, both in Ontario, Canada.
They analyzed small tissue samples taken from the wings of 20 big brown bats (Eptesicus fuscus) in two periods: in winter, when they hibernate, and in summer, when they were active. The bats, kept in a research colony at McMaster University, ranged in age from less than 1 year to just over 10 years.
After the samples were collected, the researchers measured changes in DNA methylation – a biological process related to gene regulation – between samples taken from the same animal during the active period and the hibernation period. They found that changes in DNA methylation occur in specific regions of the bat genome, and these locations appear to affect metabolism during hibernation.
“It’s pretty clear that the sites that reduce methylation in the winter are the sites that seem to have an active effect,” Wilkinson said. “Many of the genes closest to them are known to be involved in the regulation of metabolism, so they are thought to inhibit metabolism.”
Some of these genes are the same ones that Wilkinson and his research colleagues identified as “longevity genes” in a previous study. Wilkinson said there is significant overlap between hibernation genes and longevity genes, further emphasizing the link between hibernation and longer lifespans.
The earlier study also created the first epigenetic clock for bats, capable of accurately predicting the age of any bat in the wild. This clock was used in the latest study, which allowed the researchers to demonstrate that hibernation reduces the epigenetic age of a bat compared to an age-matched non-hibernating animal.
Studies like this help explain why bats have longer lifespans than expected for small, mouse-sized mammals. However, they also raise new questions.
“We still don’t really understand why some bats can live very long and others can’t,” Wilkinson said. “We have shown that those who live very long have a general ability to hibernate or to faint frequently. That seems like a consequence, but it’s not enough, because hibernating rodents don’t live for 20 years.”
Wilkinson said he plans a follow-up study to compare the epigenetic aging of big brown bats in Canada, where they hibernate, with the same species in Florida, where they do not hibernate. In doing so, Wilkinson hopes to gain an even clearer picture of the role hibernation plays in extending lifespan.