Bats in Sierra Nevada Have Adapted to Fire, Thriving After Forests Burn, Study Finds

Bats don't just survive in the face of wildfire—they thrive. According to researchers writing in the journal Scientific Reports, bat populations are not fazed by the heat—at least, not those in the Sierra Nevada mountain range in California.

Acoustic surveys were used to monitor the impact wildfire had on the region's 17 species of bats from 2014 to 2017. This included testing the effects of burn severity and its effects on species diversity.

By and large, populations appeared to benefit from the flames or, more specifically, the conditions they created, with burned forests of moderate to severe intensity hosting more species of bats than unburned forests (11 versus 8 species). Only one species (the small-footed bat) occurred most often in unburned forests.

The researchers put this preference down to forest density. While there were differences between bat species, as a group they tended to benefit from the lower density of the burned forest in comparison to the higher density of the unburned forest. This was true not only of species of bats that are known to prefer less dense, more open spaces, but those who have evolved to live in denser forests—an observation that might show how cluttered some forests have become.

Zack Steel, a postdoctoral researcher with the University of California Davis and University of California Berkeley, believes this could be the result of decades of fire suppression.

Butte Fire
The Butte Fire is seen on September 13, 2015 near San Andreas, California. New research suggests some species of bat native to California thrive in forests burned by wildfire. David McNew/Getty

The reason for this inclination towards less dense forest could come down to greater accessibility when it comes to foraging and a more diverse habitat.

As animals that rely on echolocation to track down prey, some species are naturally more tolerant of cluttered spaces than others. Typically, smaller duration calls made with higher frequency and smaller body sizes in comparison to the wing area are traits that are more adaptable to denser habitats.

Therefore, reason goes, the more diverse the habitat, the more species you can expect to find. Wildfires that lead to a more diverse habitat should then lead to more species. A less cluttered environment will also, the researchers argue, improve accessibility when it comes to foraging for prey—a conclusion backed up by a previous study monitoring bat activity in the Piliga forests in Australia, which hypothesized some species may be joined to burned forest by the abundance of insects to feast on. (Another study, based on Arizona bats, found that the effect of wildfire varies depending on the species, and raised concern about the effect of climate change—which is linked to more severe and more frequent wildfires—on the state's bat populations.) Individual bats may also use dead trees and snags, damaged by fire, as a place to roost, the researchers add.

The researchers hope the information can help with the conservation and protection of bat species, who might deal with wildfire but are facing several other threats, including habitat loss, climate change and disease. White-nose syndrome, in particular, has been devastating populations of bats across the US and Canada, where it is responsible for millions of deaths.

"This is an interesting and important study," Robert M R Barclay, a professor in biological studies at the University of Calgary, told Newsweek.

"Predictions are that wildfire frequency and severity will increase due to climate change. Understanding the effects of wildfires on biodiversity and on specific groups of organisms is thus important."

This article has been updated to include statements from Robert M R Barclay.