Love bats? Think twice about that bat box, experts say

Date:
March 29, 2021
Source:
University of Illinois College of Agricultural, Consumer and
Environmental Sciences
Summary:
Ever thought about buying or building a bat box to help bats? Think
carefully about the design and where you put it, researchers say.



FULL STORY ==========================================================================
Ever thought about buying or building a bat box to help bats? Think
carefully about the design and where you put it, University of Illinois researchers say.


========================================================================== Here's why: Bats and their pups can overheat and die in poorly designed
or placed bat boxes, and in a warming climate, it could happen more often.

Illinois bat ecologists Joy O'Keefe and Reed Crawford recently synthesized
the available data on bat boxes, also known as bat houses or artificial
roosts, to raise awareness of the issue and motivate change in bat box
design, marketing, and consumer education. Their recommendations are
published in Conservation Science and Practice.

"Conservation practitioners and homeowners are well-intentioned; they want
to help bats. Inevitably, the first thing they do is go online and buy a
bat house," says Crawford, a doctoral student in the Program in Ecology, Evolution, and Conservation Biology at Illinois. "But unfortunately,
a lot of bat houses on the market are small and painted dark colors,
and they get hot really quickly. They're likely to hurt bats if they're installed in the wrong spot.

"We're trying to highlight that there's a lot of misleading information
out there. We want to steer people away from putting up bat boxes as a
first course of action, to instead consider the risks and ask if there
is anything we can do that's going to be more beneficial for bats."
Crawford has read just about every study that's ever been done on bat
boxes, and he and O'Keefe have conducted their fair share of studies, as
well. They and other members of the bat research community have identified
a critical temperature threshold -- 104 degrees Fahrenheit or 40 Celsius
-- above which most bat species are significantly heat-stressed.



========================================================================== Although very few studies have documented temperatures inside the
countless bat boxes currently in use across the world, researchers have recorded temperatures as high as 142 degrees Fahrenheit in artificial
roosts. And they've observed bats in natural roosts moving to avoid temperatures above 97 degrees.

In many bat boxes, bats can't move around to avoid hot spots. The most
common design is a small, flat-panel box with vertical slats creating
one to four chambers. The boxes are often painted or stained dark colors,
and that can be a big part of the problem.

"We know darker boxes can be, on average, 41-43 degrees hotter than white
boxes and are more likely to overheat. Yet we see companies marketing
black boxes as preferable to bats and suitable for most U.S. climates," Crawford says. "But one hot summer day in a really tiny black bat house is probably going to kill anything that's in there. So it's very dangerous." O'Keefe, an assistant professor and wildlife extension specialist in the Department of Natural Resources and Environmental Sciences at Illinois,
adds, "Even our colleagues in cooler climates have seen a number of bat
deaths in dark-colored boxes. That's why we advocate for not painting
boxes in dark colors." But she points out that bat deaths have also
occurred in unpainted, light-wood boxes in warm climates. "Clearly, more intervention is needed than just the color of the box." Bats do like to
be warm and protected when they're sleeping and raising their young. But
when they're seeking out natural roosts in the wild, they choose spots
that allow them some flexibility to move when it gets too hot.



========================================================================== That's why Crawford and O'Keefe say if you're going to invest in a bat
box, large designs are better. For example, tall, four-sided boxes allow
bats to move up and down in space and around to the back side when the
front is being blasted by sun.

Researchers are also investigating novel materials and design elements
that are better temperature buffers than the usual plywood, including wood-cement (a molded mixture of wood shavings and cement), insulating
water chambers, and chimneys.

But regardless of design and color, placement has implications that go
beyond overheating.

"Obviously, you're going to want to avoid hanging a small, dark bat
house where it's going to get direct sun all day, especially in warmer, southern climates," Crawford says. "But we're just starting to learn about
how artificial roosts might represent ecological traps for bats. They
could be preferentially selecting the bat box because of where it is and passing over natural habitats that would keep them safer from predators
and parasites, as well as dangerously warm temperatures." O'Keefe adds,
"Bat houses can also draw bats to areas that are inappropriate.

That's one of the reasons I've moved away from advising people to put
out bat boxes as a first step in bat conservation. People need to think
about what they're drawing bats to. Do they have to cross any difficult boundaries, like busy roads, to get there? "I encourage homeowners to
think about doing something else that could benefit bats instead, like
planting native trees or wildflowers to attract insect prey, providing
clean water sources, or leaving standing dead trees wherever it is
safe to do so, as these are natural roosting habitat for bat box users." ========================================================================== Story Source: Materials provided by University_of_Illinois_College_of_Agricultural,_Consumer and_Environmental_Sciences. Original written by Lauren Quinn. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Reed D. Crawford, Joy M. O'Keefe. Avoiding a conservation pitfall:
Considering the risks of unsuitably hot bat boxes. Conservation
Science and Practice, 2021; DOI: 10.1111/csp2.412 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/03/210329122749.htm

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