Several species of bats that spend
the summer in Rhode Island have experienced dramatic declines in their
populations due to white nose syndrome, the fungal disease discovered in 2007
that infects bats in the caves and mines where they hibernate for the
winter. Little brown bats, for instance,
the most abundant species in the region prior to the outbreak and the species
most likely to be found breeding in attics and barns during the summer, have
declined by about 90 percent in the Northeast, and northern long-eared bats
have lost more than 98 percent of their population.
Perhaps the only good news that has
resulted from the disease is that bat biologists have been forced to think
out-of-the-box for ways to protect the remaining populations of bats. They’ve
begun to re-think the concept of hibernation caves – called hibernacula – in
hopes of discovering previously unknown locations where bats may be spending
the winter.
Until very recently, it was not
believed that many bats wintered in Rhode Island. Those species that migrate,
including hoary, silver-haired and red bats, head south well before the winter
freeze. And those that hibernate underground – like little brown, northern
long-eared and tri-colored bats – were all thought to migrate to caves and
mines in New Hampshire, Vermont, and New York. And they do. But, it turns out,
not all of them.
After a biologist in New Hampshire
discovered bats hibernating in abandoned man-made structures along that state’s
coast, Charlie Brown, the wildlife biologist responsible for bat conservation
for the Rhode Island Department of Environmental Management, began to seek out
sites where the animals may be over-wintering in the Ocean State.
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| Little brown bats with white nose syndrome (USFWS) |
“To my knowledge, no effort had been
made previously to survey those kinds of sites,” Brown said. “But it got us
thinking about what constitutes a hibernaculum. Instead of caves and mines, are
there alternative sites that bats might use that we haven’t noticed in the
past? And might these places be the last holdouts for the species?”
Beginning in 2011, Brown began
identifying possible facilities, most on state-owned land, that might have the
appropriate conditions.
“Bats are finicky about their
environment. Those that typically use subterranean structures to hibernate
require a stable environment with high humidity and low temperatures
consistently around 35 to 40 degrees in winter,” Brown explained. “There can’t
be much airflow through the structure that might change those conditions.”
He said the bats also require a
location that is undisturbed by frequent human visitation. “Every time they’re aroused, they burn
calories,” Brown said.
After several years of using a
headlamp and flashlight to explore abandoned structures throughout the coastal
regions of Rhode Island, Brown has identified four structures where small
numbers of bats have been found hibernating. A total of less than 100 bats have
been recorded at the four sites, with big brown bats the most common species
detected. Northern long-eared and tri-colored bats have also been observed.
Peter August, a biologist at the University of Rhode Island who has studied tropical bats, isn’t surprised that
Brown has discovered big brown bats overwintering in Rhode Island. He said that
species typically hibernates within 30 miles of their summer roost. “We just
don’t notice them here because they’re hibernating,” he said. “If we continue
to have warm weather like we have, I wouldn’t be at all surprised if people
start seeing bats flying around outside this winter.” Finding the other two
species, however, is a surprise.
Brown banded eight of the
hibernating big brown bats he discovered, and four of them returned to the same
site the following year, which suggests they have a degree of site fidelity.
But the small numbers of bats he has found so far may indicate that the
structures do not provide optimal conditions for hibernation. And Brown has no
idea how long they may have been in use.
“We don’t see skeletons of bats that would suggest that 10 years
ago there were many more using these sites than today,” said Brown, who won’t
reveal the location of the sites in order to reduce the likely hood of
disturbance. “I assume that these facilities became appropriate as hibernacula
at some point, maybe because they were abandoned recently or are not used in
the same way any more.”
The DEM biologist will continue
searching smaller structures this winter in hopes of finding additional bats.
“We’d like to find more sites. Bats
may use cisterns, sewage systems, military-type structures, summer homes, and
other places we haven’t looked at yet,” he said. “We’ve looked at most of the
larger structures, but we’re sure there are other smaller places out there.”
As exciting as it is to find a
diversity of hibernating bats in Rhode Island, Brown isn’t convinced that these
sites are protecting local bats from white nose syndrome, even after tests of
samples collected last year from the structures and from the bats themselves
all came back negative.
“The fungus was not detected, but we
can’t say it’s not there,” Brown said. “Given that the bats move around the
landscape and interact with bats from infected caves, it’s hard to imagine that
our area hasn’t been affected or that we’re insulated from it. That would be
nice, but we don’t know that yet.”
Those who observe a bat in a home or
other structure in winter are encouraged to contact Brown at 401-789-7481 or charles.brown@dem.ri.gov. He also monitors maternity colonies in the summer months and
asks those with large numbers of bats in their attics or barns in the summer to
contact him. And if you find a bat in the living space of your home, he
recommends contacting the Rhode Island Department of Health for a health
screening, as bats are known to carry rabies and other diseases.
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