Bats, Bat Houses, and White-Nose Syndrome 2009

Mosquito control is a perennial topic on the Flatbush Family Network, one of the numerous email discussion groups which cover the different neighborhoods of Brooklyn. Bat houses invariably come up as a way of attracting a natural predator to keep mosquito populations in check. Here I’m reprising and updating my posts on these and related topics from last year.

White-Nose Syndrome (WNS)

Last Spring I wrote about White-Nose Syndrome (WNS). A breakthrough that occurred just in the past few months is that the “White-Nose” has been identified as a group of previously unknown species of Geomyces fungus. It’s still unknown whether it’s a symptom – such as an opportunistic infection – or a cause or contributor.

Bats exhibiting white-nose syndrome in Hailes Cave, Albany County, NY, one of the first caves in which WNS was observed. Photo: Nancy Heaslip, NYS DEC.

Bob Hoke of the District of Columbia Grotto (DCG) of the National Speleological Society (NSS) maintains an excellent chronology of WNS news and understanding. WNS has already killed hundreds of thousands of bats across the northeast over the past four winters. Mortality has been as high as 90% in some caves. It’s estimated that 75% of northeastern bats have died in just four years. Unfortunately, it continues to spread; for the first time, it’s also been found or suspected in New Hampshire, New Jersey, Pennsylania, Virginia and West Virginia.

Map of occurrence of White Nose Syndrome by county as of March 4, 2009. WNS was later confirmed in Virginia. Credit: courtesy of Cal Butchkoski, Pennsylvania Game Commission
Counties with White Nose Syndrome

Because of the high mortality, rapid spread, and still-unknown causes of the disease, the U.S. Fish and Wildlife Service (US FWS) has issued a cave advisory to suspend all caving activities in affected states, and take precautions in states where WNS has not yet been detected:

The evidence collected to date indicates that human activity in caves and mines may be assisting the spread of WNS. Therefore, the U.S. Fish and Wildlife Service is recommending actions to reduce the risks of further spread of WNS:

  1. A voluntary moratorium on caving in states with confirmed WNS and all adjoining states;
  2. Nationally, in states not WNS-affected or adjoining states, use clothing and gear that has never been in caves in WNS-affected or adjoining states;
  3. State and federal conservation agencies should evaluate scientific activities for their potential to spread WNS; and
  4. Nationally, researchers should use clothing and gear that has never been in caves in a WNS-affected or adjoining state.

This also applies to mines used by cavers.

These recommendations will remain in effect until the mechanisms behind transmission of WNS are understood, and/or the means to mitigate the risk of human-assisted transport are developed.

There was a big thing that came out in the environmental reports last year that chemical mosquito killers are quite bad for the environment and killed more than just mosquitoes. They might even be part of the reason why there is a bacteria/virus killing off northeastern bats. Although, scientists haven’t found anything conclusive it seems.
– via Flatbush Family Network

WNS research is ongoing, but it’s still not known what the cause is. A plausible explanation is immunodeficiency caused by environmental contamination, such as insecticides sprayed for West Nile Virus, but again, that’s just one of several hypotheses being explored by researchers. A pathogen such as a virus, bacteria or fungus is likely due to the patterns by which it’s spreading.

Bat Houses

Bat houses seem like a great idea. At night, bats eat about 1,000 pesky insects an hour. I don’t know how one attracts bats to your bat house but I’ve seen them in the evening in Prospect Park, amazing little creatures that they are.
– via Flatbush Family Network

I wrote about bat houses last year. Bats have specific requirements for roosting sites. Most of the houses I’ve seen commercially available are too small or lacking in other requirements. The National Wildlife Federation (NWF) article, “Why I Built a Bat House,” contains detailed instructions for building a house that meets current knowledge about bats roosting needs.

The bat house I purchased last year from Bat Conservation International before I installed it on the side of the second floor porch – my “tree fort” – at the back of my house.
Bat House

Note that this is the time of year when bats are looking for their “summer homes.” I put mine up mid-April last year, which was a little late. I’m hoping they find it and set up house this year!

General information about bats

Is there ANY danger to my 4 year old son? Do bats poop/pee/spit anything bad for him? Do they really only come out at night?
– via Flatbush Family Network

Bats really do only come out at night. You’re most likely to see them at dusk, when they leave their roosts, and dawn, when they return. At the end of last summer, I saw a few on my block flying amidst the gaps between the canopies of the street trees. They seemed to be feasting on the insects attracted to the street lights.

Many people are concerned about rabies. While sensible caution is warranted, the risk is extremely low. In New York City, you’re more likely to contract West Nile Virus (WNV), which bats help combat by eating mosquitoes which carry the virus. If you see any normally nocturnal animal – such as a bat, raccoon or opossum – out in the open during the day, keep children and pets away from it and notify animal control by calling 311.


Related Content

Rabies in NYC: Facts and Figures, 2008-07-08
Bat Houses, 2008-04-13
Northeastern Bats in Peril, 2008-03-18
Other posts about bats



Bats of New York, Eileen Stegemann and Al Hicks, Conservationist, February 2008, NYSDEC
Bat Conservation International (BCI)

Bat Houses

Why I Built a Bat House, Carla Brown, National Wildlife Federation (NWF) (H/T Sara S. via Flatbush Family Network)
Bats Wanted, Al Hicks and Eileen Stegemann, Conservationist, February 2008, NYSDEC
The importance of bat houses, Organization for Bat Conservation
The Bat House Forum

White-Nose Syndrome

An excellent chronology of WNS is maintained by Bob Hoke of the District of Columbia Grotto (DCG) of the National Speleological Society (NSS).

White-Nose Syndrome Confirmed in VA Bats, WHSV, Richmond, VA, 2009-04-02
Cave activity discouraged to help protect bats from deadly white-nose syndrome, Press Release, U.S. Fish & Wildlife Service, 2009-03-26
Fungus Kills About 90 Percent Of Connecticut’s Bats, Rinker Buck, Hartford Courant, 2009-03-18 (H/T NewYorkology via Twitter)
Newly Identified Fungus Implicated in White-Nose Syndrome in Bats, Press Release, U.S. Department of the Interior, U.S. Geological Survey (USGS), 2008-10-31
Bats dying off across western Maine, Maine Sun Journal, 2008-07-19 (H/T Center for Biological Diversity)
Dying Bats in the Northeast Remain a Mystery, USGS Newsroom, 2008-05-09
First It Was Bees, Now It’s Bats That Are Dying, Natural News, 2008-04-11
Bats in the Region Are Dying From a Mysterious Ailment, Litchfield County Times, 2008-04-03
Bats Perish, and No One Knows Why, New York Times Science Section, 2008-03-25
Bat Die-Off Prompts Investigation, Environment DEC, March 2008, NYSDEC

White-nose Syndrome Threatens New York’s Bats, New York State Department of Environmental Conservation (NYSDEC)
White-Nose Syndrome, Pennsylvania Game Commission (PGC)
White-Nose Syndrome in bats: Something is killing our bats, U.S. Fish & Wildlife Service, Northeast Region

Mystery Disease Kills U.S. Bats, Bat Conservation International
Bat Crisis: The White-Nose Syndrome, Center for Biological Diversity
White Nose Syndrome Page, Liaison on White Nose Syndrome, National Speleological Society (NSS)

Something is killing our bats: The white-nose syndrome mystery, U.S. Fish and Wildlife Service

Wikipedia: White-nose syndrome

Bat Houses

Corrected 2008.04.17: Restored missing photos. Other edits.
Updated 2008.04.16: In response to Manhattan Users Guide, provided additional explanation of why I put up a bat house: to help prevent their extinction.
Updated 2008.04.15: Added inline links, plus link to BatCatalog, BCI’s online store.

The new bat house

Today I installed my first bat house, on the side of my tree fort, the second floor porch on the back of our house. It’s a two-chambered house which I purchased online three weeks ago from BatCatalog, the online store of Bat Conservation International (BCI). (Disclosure: I’m a supporting member of BCI.)

BCI has free plans for a single-chambered house [PDF] on their Web site, and they have a handbook of many different plans for folks to design and build their own houses. I chose a pre-built house, for my first one. Because it’s my first, I wanted one that was well-designed and built. I also wanted to get one installed in time, possibly, for this year’s summer breeding season. I’m handy, but I procrastinate; if I started building a house now, I’d be lucky if I got it done for NEXT year.


Why build (or buy) and install a bat house?

I know some of you are thinking, “WHY?!”

Why build a bat house? The simple answer is because having bats in the area is an easy way to observe nature at her finest, and the bats will provide a guaranteed show every warm evening of the summer season. Bats are insect eating-machines that may help keep troublesome insect populations in check. In addition, providing bat houses is one method of encouraging bats to relocate their colonies out of buildings.
Bats Wanted, Conservationist, February 2008, NYS DEC

This year, there is an additional, more urgent, reason. I wrote a few weeks ago about the disease that is wiping out bats hibernating in their Winter colonies across the northeast. The disease has been confirmed in four states so far: New York, Vermont, Massachusetts, and Connecticut. Mortality has been estimated to be as high as 90% in some of their hibernation caves. If the cause cannot be discovered and eliminated, we may lose entire species of bats in just a few years.

Bats are not prolific breeders. A mating pair may have a single pup a season. Even if scientists find a cause for the disease, and can prevent further mortality, it will take decades for bats to recover the numbers they’ve lost in a single season.

Artificial roosts, such as my new bat house, are bats’ “summer homes” and, more important, their nurseries: they use these to bear and raise their young. It’s my hope that by creating more summer roosting and nursery sites, we can increase their health and rates of survival during the year. They need all the help we can give them.

Where can bat houses be used?

Where will bat houses be effective? And where should they be placed? The answer, if familiar, is location, location, and location:

  • It should be located near fresh water, no more than 1/2 mile away. Houses within 1/4 mile have higher rates of occupancy.
  • The house must be mounted at least 12 feet high, either on a free-standing pole or the side of a building.
  • Away from bright lights.
  • They must be away from tree limbs and other aerial barriers such as wires which can create obstacles to finding the bat house or provide launches for predators.

In an urban area, it’s a challenge to find these conditions. I live just over a half-mile, as the bat flies, from Prospect Lake in Prospect Park, the largest body of fresh water around. But my area is more suburban than urban, with large lots and open yards. Many of my neighbors have “water features” in their gardens: ponds or pools which can serve as alternate sources of fresh water.

The bat house in place
The bat house in place

I think I have a good place for my bat house: on the side of my tree fort, facing south-southeast. The garden beds below are in full sun all summer. Even in Winter, when the sun is low and the beds are shaded by our neighbor’s house, the bat house is mounted high enough to receive full sun. My neighbor has a security light, but the house is placed behind its main field of illumination, out of direct line of the light itself.

Most nursery colonies of bats choose roosts within 1/4 mile of water, preferably a stream, river or lake. Greatest bat-house success has been achieved in areas of diverse habitat, especially where there is a mixture of varied agricultural use and natural vegetation. Bat houses are most likely to succeed in regions where bats are already attempting to live in buildings.
Criteria for Successful Bat Houses [PDF], BCI

Bat houses should be mounted on buildings or poles. Houses mounted on trees or metal siding are seldom used. Wood, brick or stone buildings with proper solar exposure are excellent choices, and houses mounted under eaves are often successful. Single-chamber houses work best when mounted on buildings. Mounting two bat houses back-to-back on poles (with one facing north and the other south) is ideal. Place houses 3/4-inch apart and cover both with a galvanized metal roof to protect the center roosting space from rain. All bat houses should be mounted at least 12 feet above ground, and 15 to 20 feet is better. Bat houses should not be lit by bright lights.
Criteria for Successful Bat Houses [PDF], BCI

Houses mounted on the sides of buildings or on metal poles provide the best protection from predators. Metal predator guards may be helpful, especially on wooden poles. Bats may find bat houses more quickly if they are located along forest or water edges where bats tend to fly. However, they should be placed at least 20 to 25 feet from the nearest tree branches, wires or other potential perches for aerial predators.
Criteria for Successful Bat Houses [PDF], BCI

Where you mount your bat house plays a major role in the internal temperature. Houses can be mounted on such structures as poles, sides of buildings and tall trees without obstructions. Houses placed on poles and structures tend to become occupied quicker than houses placed on trees. Bat houses should face south to southeast to take advantage of the morning sun. In northern states and Canada, bat houses need to receive at least 6 to 8 hours of direct sunlight. It is also advantageous to paint the house black to absorb plenty of heat (when baby bats are born, they need it very warm). Use non-toxic, latex paint to paint your bat house and only paint the outside. Your bat house should be mounted at least 15 feet above the ground, the higher the house the greater the chance of attracting bats.
Where to put up a bat house in the Northeastern United States, Organization for Bat Conservation

Bat houses installed on buildings or poles are easier for bats to locate, have greater occupancy rates and are occupied two and a half times faster than those mounted on trees.
Attracting Bats [PDF], BCI

What makes a well-designed bat house?

The bat house before installation
Bat House

Successful bat houses are much larger than one might think. Take a look at the photo above. The house is leaning against a table of standard height. That’s a garden spade next to the bat house for scale.

Bats are communal creatures. Because they’re so small, they need each other to keep warm at night. The more bats, the better. The larger the bat house, the better. This is especially important for infant survival in nursery colonies. My relatively small two-chambered bat house can shelter up to 100-150 bats.

The spacing of the chambers is important. Just large enough that the bats can crawl up inside, small enough to reduce the attractiveness to potential problem nest-builders like wasps and hornets.

The bottom of the bat house is open. Guano will fall down to the ground below. It doesn’t collect in the bat house, so it doesn’t need to get cleaned out.

The key to a successful bat house in the northeast’s cooler climate is to keep the house hot. Be sure to seal the upper portions so that warm air cannot escape, paint the house a dark color, and place it in the sunniest location you have that is near cover and not far from water. Maintenance, such as repairing a warping exterior that no longer traps warm air, will be an issue over time, so consider providing some kind of protective cover.
Bats Wanted, Conservationist, February 2008, NYS DEC

Only in the most extreme southwest should bat houses be painted a light color. In my area, a dark brown would also work with a bat house placed in ideal conditions. Because my bat house is backed by an open porch, and not the house itself, I chose the darkest color, a flat black, to compensate for the lack of insulation one would get from mounting on the side of a house.

When should bat houses be installed?

According to DEC’s Conservationist magazine, in New York State, bat houses are most likely to attract either little brown or big brown bats. So, where do you get the bats?

Bats have to find new roosts on their own. Existing evidence strongly suggests that lures or attractants (including bat guano) will NOT attract bats to a bat house. Bats investigate new roosting opportunities while foraging at night, and they are expert at detecting crevices, cracks, nooks and crannies that offer shelter from the elements and predators.
Attracting Bats [PDF], BCI

Bat houses can be installed at any time. However, it may take up to two years for bats to “adopt” a shelter. The best time to install a new bat house is in late Winter/early Spring, before bats emerge from winter hibernation and begin seeking summer nursery sites. I saw a bat flying at dusk at the Brooklyn Botanic Garden last Thursday, during our botany class walkaround. Now may be too late for my bat house for this year. We’ll see what happens.

Bats return from migration and awaken from hibernation as early as March in most of the U.S., but stay active year-round in the extreme southern U.S. They will be abundant through out the summer and into late fall. Most houses used by bats are occupied in the first 1 to 6 months (during the first summer the bat house was erected). If bats do not roost in your house by the end of the second summer, move the house to another location.
Where to put up a bat house in the Northeastern United States, Organization for Bat Conservation


Related Content

Northeastern Bats in Peril, March 18, 2008
Other posts about bats and White-Nose Syndrome


Bats Wanted, Conservationist, February 2008, New York State Department of Environmental Conservation
Bat Conservation International (BCI)
BatCatalog, BCI’s online store
The importance of bat houses, Organization for Bat Conservation
The Bat House Forum
Wikipedia: Bats

December 8, Red Hook: Observing the Edge

This looks interesting:

Brooklynites know better than anyone the havoc that development can wreak on a habitat. So on Saturday, Dec. 8, the Kentler International Drawing Space in Red Hook will host an artist’s talk on “Observing the Edge,” the gallery’s current show, which features works on paper relating to flora and fauna with habitats threatened by progressive development.

… anyone who has seen plants, or any other living creatures, displaced by development will surely want to take notice.
Cutting ‘Edge’, Daniel Goldberg, The Brooklyn Paper

(Note: The Brooklyn Paper gave the date incorrectly as 12/4.)


Kentler International Drawing Space
353 Van Brunt Street
Red Hook/Brooklyn, New York 11231
Tel: 718-875-2098

Article, Fall 2005: The Changing Flora of the New York Metropolitan Region

The authors compare past distribution data from historical records, and current data from Brooklyn Botanic Garden’s New York Metropolitan Flora Project to determine changes in distribution over the past century. They further compare these changes between native and introduced species within the same genus, such as Celastrus scandens, American bittersweet (native) and Celastrus orbiculata (or C. orbiculata), Oriental bittersweet (introduced, and invasive), or Lonicera sempervirens, Trumpet honeysuckle (native) and Lonicera japonica, Japanese honeysuckle (introduced, and invasive).

We statistically analyzed 100 years of herbarium specimen data for woody plants in the New York metropolitan region in order to measure the floristic changes of this area. Change Index values were computed for 224 of the region’s 556 woody species to provide a specific measure of whether these species are expanding, contracting, or stable. The results show that, in general, nonnative invasive species are spreading rapidly in the region, while native species are in slight decline.
The Changing Flora of the New York Metropolitan Region


The Changing Flora of the New York Metropolitan Region, Urban Habitats, Volume 3, Number 1, Fall 2005, Brooklyn Botanic Garden, 1000 Washington Avenue, Brooklyn, NY 11225