Together with colleagues, Dr. Christopher Turbill has made some worrying findings about the safety of bat boxes for Eptesicus fuscus— big brown bats. Their research period was in Lillooet, British Columbia. Their research demonstrates that temperature inside these artificial roosts can exceed 50 degrees Celsius during extreme heat events. This extreme heat is creating deadly threats to the bat populations that depend on them. Science is clearly calling for action to confront climate-related perils to these remarkable nighttime pollinators. Continued exposure to the increasing extreme heat will have catastrophic effects on their health and safety.
That’s why the study’s recent revelations are particularly notable as rising temperatures from climate change are increasingly felt across the country. Roosting caves require unique conditions to serve bats as optimal roosting habitat. Unfortunately, conventional bat houses no longer seem to provide the safe havens they once did. Researchers are advocating for smarter designs in bat roosts. They want to improve how they serve the needs of these keystone species.
The Dangers of Heatwaves
Dr. Turbill’s recent research highlights why temperature extremes are a key limit for bats. He wants communities to understand the risks of bat boxes becoming dangerously hot. It’s that prolonged exposure to all that extreme heat that is hugely problematic. Ruvinda de Mel, a PhD candidate at the University of New England, resonates with this worry. She has recorded similar instances of mortality among Australian bats during heat events.
“Prolonged exposure to that high heat is also extremely problematic,” – Ruvinda de Mel
Our research points to links with previous events. One notable instance was back in 2017, when bats perished due to the extreme heat while roosting. Australia has seen several of these mass die-offs during recent heatwave conditions. In response, researchers are urgently exploring methods to improve artificial roosts to better advance bat conservation efforts.
In response to this, Dr. Shannon Currie explained that bat boxes can still be harmful despite keeping temperatures at about 40 degrees Celsius. Extended exposure to those conditions can be detrimental to bats. “If you are providing artificial roosts, they should be made up of varied materials and placed in different orientations on trees or around a home to give different opportunities for roosting,” she stated.
The Need for Innovation in Bat Housing
In reaction to these alarming results, Dr. Turbill suggests moving away from conventional bat boxes and creating “bat condos.” These structures would include several independent chambers at different temperature gradients, providing bats with more options and more thermal comfort. This type of policy is already starting to take hold in the United States but is underused throughout the rest of the world.
“I think one of the best things to do is to try and provide multiple microclimates within the bat box,” – Ruvinda de Mel
Dr. Currie is a proponent of this approach, explaining that diversity in roosting options is key to bat survival. “Diversity in everything, in animals, in roosts, in plants. That’s really the best way to go about things,” she remarked.
Bat condos can be an important tool in protecting bat populations from the heat that is becoming a more prevalent aspect of climate change. Moving from single-unit bat boxes to multi-unit bat houses allows bats greater access to cooler or shaded areas. This modification increases their habitats, promotes their overall health and well-being.
The Importance of Natural Roosting Sites
Though artificial roosts offer important assistance, researchers emphasize the need to protect natural habitats in which bats flourish. In Australia, over half of bat species rely on hollow-bearing trees for their roosts. These trees provide hollows that only form with age in the ecosystem. Sadly, habitat destruction has forced species such as Gould’s wattled bat to find shelter in human-built structures.
Dr. Currie emphasized the significance of maintaining old trees: “Keeping old trees upright is going to benefit so many species beyond bats, but definitely will benefit bats.” Natural roosts are vigorously defended by conservationists. By conserving these habitats, they not only help bats but benefit countless other wildlife.
“Bats do tend to be quite faithful to certain roosts, so there is the risk that they keep returning to a roost that they’ve used in the past and extreme heat events become more severe,” – Dr. Christopher Turbill
With climate change likely to exacerbate temperatures in the coming years, knowing why bats select certain roosts over others will be critical. Rather, they seem to select roosts based on understanding the layout of sunlight sources more than the thermal preferences in temperature.
