Friends have asked how to attract bats to their yard. My yard is barely large enough for a hibachi and I have no experience with bat houses. But here are some tips from reading and talking to people:
1. If you want to attract bats, attract bat food.
Water: If you have no stream or pond nearby, consider providing a pool for bats to drink from. It can be small, but make sure the area around it is clear so bats feel safe from predators. The water will also attract insects (a.k.a. bat treats).
Plants: Many sources recommend fragrant plants that attract moths and other night-time pollinators. This article from Maryland has planting suggestions and landscaping tips. (Does anyone out there know of any real research on garden plants that encourage bat visitation?) For UK residents: “Bats in the Garden” seed mixture.
Coverage: A wooded border to your yard will allow bats to retreat if they feel threatened. Cats prowling your yard might make bats wary.
Pesticides: Don’t use them. They are a major cause of population decline for bats and other animals.
Lighting: An insect-attracting light in your yard could bring in hungry bats. But don’t have light shining on your bat house. Many bat species have adapted to hunting around street lamps. The old bluish carbon vapor lamps are best. The newer energy-saver yellow-orange lamps attract fewer insects and bats. More on bats and streetlamps.
2. If you want bats to stay, provide roost sites:
Bat houses: BCI's North American Bat House Research Project has info on purchasing, building, and locating bat houses, including region-specific advice and a research archive. Bats are picky about roost structures and sites, so it pays to study first.
Habitat: Encourage your community and state to conserve forests and caves. Even a small local woods can be great habitat for bats. If you are lucky enough to have old dying trees on your property, don’t cut them down. Many species of bats like to roost in tree hollows, in woodpecker holes, and under loose bark.
SCOTLAND - A £50m golf resort project is waiting for 400 mother pipistrelles to finish raising their young. The bats roost in a farmhouse on a future fairway. Strict UK bat protection law prevents the disturbance of an inhabited bat roost. Scottish National Heritage placed roosting boxes on the site for next year's maternity season.
Ohio Congressman Steve LaTourette is working to resolve a problem between two constituents: a community with a stalled school construction project and a community of Indiana bats. (Okay, bats don’t vote.) A pregnant Indiana bat was found at the school site. The bat’s federally endangered status required the construction to halt. The Congressman’s press release mentions a recent habitat survey
...that pinpoints 20 possible trees where a maternal roosting colony might be located. LaTourette said only a handful of trees are located in areas that could be disturbed by construction. “My belief is that construction can go forward with little or no disruption to possible bat habitat,” LaTourette said. “I also made it clear that we are willing to do all that is necessary to protect the bat and build a school, and that this won’t be an ‘either or’ proposition."
I’m no expert on the Indiana bat, but I suspect construction activity would disrupt the maternity season and render any nearby roosts unusable, even if they spare most of the trees. But the Congressman should be commended for acknowledging both sides of the issue. An aerial photo of the site looks like good bat habitat -- big open areas, lots of woods, and ponds with clear swoop zones. Drawings of the future school show how the community has invested in planning and funding since September 2002. It’s a thorny problem. I wonder what the kids and teachers in Ashtabula, Ohio think about all this.
Indiana bat in tree roost.
A mother Indiana bat (Myotis sodalis) is choosy about her housing. This species usually prefers to roost under exfoliating bark. It’s a short-lived arrangement because loose bark eventually falls off the tree. BCI states that “a continually emerging mosaic of multi-aged trees needs to become available from year to year which can serve as roost sites. Moreover, like many cavity or crevice dwelling bats, Indiana [bats] switch roosts often throughout the summer maternity season.” Loss of summer roosts, foraging grounds, and hibernation caves contribute to this species’ population decline.
In Missouri, Mark Twain National Forest has plans to protect their Indiana bats’ habitat – which includes a maternity colony. "We are looking first to protect known occupied roosting trees," Jody Eberly, biologist for the National Forest said. "We must also provide a full range of habitat for Indiana bats including sustained foraging habitat and roosting trees, which can only be provided by careful, but active management of the area."
BCI - Indiana bat species info
Ohio Division of Wildlife - Indiana Bat info
Missouri Department of Conservation - Indiana Bat Guidesheet
You don’t often see bats in business news. A German biotech is working deals for a bat-inspired drug. When the vampire bat (Desmodus rotundus) feeds on its animal prey, a special enzyme in its saliva flows into the wound, preventing blood clotting, and allowing the bat to feed for up to thirty minutes. A genetically-engineered version of this enzyme, currently in mid-stage trials, looks promising as a clot-busting treatment for stroke victims.
Here’s a bat-friendly article about the drug’s original research, with nice photos of vampire bats. Wouldn’t it be nice if some of the drug's future profit could go to bat conservation?
There are only three species of vampire bats -- all in Latin America.
The vampire bat may be unaware of its gift to humanity. However, vampires practice altruism within their communities. Adult bats will share meals with other hungry adults, a rare behavior in the animal kingdom.
Another vampire story: A colony of white-winged vampires (Diaemus youngii) in Trinidad were facing eradication. They were brought to New Mexico where a naturalist found creative ways to adapt them to life indoors.
African Bat Conservation News [big PDF file] is a free publication oriented to researchers. If you're an amateur naturalist like me, you'll enjoy the many photos of African bat species. Especially the Myotis welwitschii with its freckled face and wings.
Africa has a wealth of bat species, but not much historic data for conservation assessment. One goal of the newsletter is to collect unpublished field notes -- which can assist population monitoring. The editor writes: "Even if a researcher only visits a site once in their lifetime, that visit could form baseline information for future trends in populations in the area." May they get much useful data and support!
I like this field guide: Beginners Guide to Bats. Well-organized with color-coding and icons for roosting and flying behavior. Consistent and complete data for each species, including echolocation frequencies. Beautiful photos. The state lists for USA and Canada tell which species are common or uncommon for that state.