While the study was done in Canada, lead author Ruvinda de Mel, a PhD candidate at the University of New England, said there have been cases of Australian bats succumbing to the heat in bat boxes as well.<\/p>\n
He added that bat boxes needed to be thoughtfully built to prevent them getting too hot.<\/p>\n
“We wanted to see if this conservation tool that’s so ubiquitously used has any issues attached to it, and if there are, how we can mitigate them.”<\/p>\n
Checking bat box safety<\/p>\n
The researchers studied big brown bats (Eptesicus fuscus) in Lillooet, in western Canada.<\/p>\n
“Bat boxes were practically everywhere,” Mr de Mel said, adding that the residents and First Nations community of Lillooet were passionate about conserving bats and other wildlife.<\/p>\n
“They want to make sure the birds and the bats and everything around them are fine, so it’s up to us to try and provide them with the best tools possible.”<\/p>\n
<\/p>\n
Micro bats crawl into these homes \u2013 particularly during the cooler months \u2013 and leave little scratch marks on the outside so you know they are being used. (ABC Capricornia: Erin Semmler)<\/p>\n
The team captured 22 bats \u2014 11 female and 11 male \u2014 and spent a few hours with each one in a field laboratory before releasing them.<\/p>\n
They monitored each bat’s breathing at different temperatures, tracking how much carbon dioxide they exhaled and how much water they lost.<\/p>\n
This gave the team data which they could use to calculate how long a bat could withstand higher temperatures.<\/p>\n
In the same summer month, the team recorded temperatures in existing bat boxes.<\/p>\n
While that month, they found the boxes remained a safe temperature, they used their data to predict how bats would fare inside the boxes during heatwaves the area had sweltered through a few years prior.<\/p>\n
<\/p>\n
Species like the big brown bat can take a drink of water while on the fly. (iNaturalist: Jos\u00e9 G. Mart\u00ednez-Fonseca<\/a>, Big brown bat<\/a>, CC BY-NC 4.0<\/a>)<\/p>\n They found the boxes could exceed 50 degrees Celsius during heatwaves, which would be deadly for the bats.<\/p>\n Just as dangerously, the boxes could hover at slightly lower temperatures of around 40C for hours at a time.<\/p>\n “Prolonged exposure to that high heat is also extremely problematic,” Mr de Mel said.<\/p>\n Christopher Turbill, an ecologist at the University of Western Sydney who wasn’t involved in the study, said the research was “powerful” in the way it combined physiological data with environmental measures.<\/p>\n Such information , Dr Turbill said, would be useful for understanding how a bat could handle a rapidly changing climate.<\/p>\n “We can make pretty firm predictions and we can understand the physiology underlying those predictions,” Dr Turbill said.<\/p>\n Mr de Mel is now working on more general modelling that can help scientists understand what conditions various bat species can handle.<\/p>\n Do Australian bats face the same risk?<\/p>\n Mr de Mel said different species of bat would have different physiological limits.<\/p>\n But he pointed out plenty of documented cases of Australian bat mortality in heat, including a 2017 case<\/a> where bats died in a bat box, and multiple mass die-offs during heatwaves<\/a>.<\/p>\n Shannon Currie, an ecologist at the University of Melbourne who wasn’t involved in the study, said Australian bats were often particularly dependent on very old trees.<\/p>\n Loss of old trees has prompted Australian species like Gould’s wattled bat (Chalinolobus gouldii) to shift to bat boxes. (iNaturalist: chocolatebacon<\/a>, Gould’s wattled bat<\/a>, CC BY-NC 4.0<\/a>)<\/p>\n Unlike Europe and North America, where woodpeckers make plenty of suitable bat homes, hollows in Australian trees only form with age, Dr Currie said.<\/p>\n “As eucalypts get old, the bark begins to peel away from the trunk a little bit, and that’s an optimal roosting location for many, many bats,” she added.<\/p>\n This makes Australian bats good at choosing the right spot to roost based on temperature, because they’ll often seek out the side of a tree which gains the right amount of sunlight.<\/p>\n But climate change could render even natural habitats more dangerous for bats.<\/p>\n Dr Currie warned that rising temperatures from climate change could make traditional roosts dangerously hot.<\/p>\n “They’ll likely select a roost based on their knowledge of the position of the sun in the sky, but not necessarily how warm that roost will get.”<\/p>\n Bats also need warmer temperatures during the winter, and when rearing their young.<\/p>\n Dr Turbill feared that roosts could become “ecological traps” for bats.<\/p>\n “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,” he said.<\/p>\n How to make safe bat roosts in your garden<\/p>\n Despite the study’s findings, Mr de Mel reiterated that boxes were an excellent conservation tool if they were designed well.<\/p>\n To make existing bat boxes safer, he suggested:<\/p>\n painting boxes white to reflect sunlightmoving them to shaded places to prevent them from getting extremely hot.<\/p>\n He also recommended shifting from a “bat box” to a “bat condo”: structures that are designed to have multiple different temperatures inside them, and are popular in the US.<\/p>\n “I think one of the best things to do is to try and provide multiple microclimates within the bat box.”<\/p>\n This can be done by creating sections of the box with different levels of insulation, adding chimneys, or placing the box in partial sunlight, for example.<\/p>\n Bats can then enjoy warmer temperatures when they need them in winter.<\/p>\n “It’s a case of providing the bat choice within that artificial structure,” Mr de Mel said.<\/p>\n Chimneys and insulation can also help to regulate bat box temperature. (iNaturalist: Brittany Porter<\/a>, Lesser long-eared bat<\/a>, CC BY-NC 4.0<\/a>)<\/p>\n Dr Currie agreed.<\/p>\n “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.”<\/p>\n She also recommended keeping old stands of trees wherever possible.<\/p>\n “Keeping old trees upright is going to benefit so many species beyond bats, but definitely will benefit bats,” she said.<\/p>\n Making insect-friendly gardens also provided bats with a good food source, alongside helping other native species.<\/p>\n “Diversity in everything, in animals, in roosts, in plants. That’s really the best way to go about things,” Dr Currie said.<\/p>\n<\/p>\n
<\/p>\n