Saturday, October 6, 2012

Building a batbox for the zoo

I volunteer at the Brandywine Zoo and I was asked to build a batbox for an Earth Day project. I never got around to writing a blog entry for it.

After a great deal of research, I designed a small bachelor batbox for display. This is probably the smallest batbox you can build with any hope to have it lived in.

Putting up a bat roosting box can help replace lost or degraded habitat that has been contributing to the decline of bat populations throughout North America. 

Bat boxes located near a permanent source of water, especially a marsh, lake or river, are the most likely to attract bats. Bat houses should be hung roughly twelve to fifteen feet above the ground, sheltered as much as possible from the wind. Don't be discouraged if conditions for your bat house are not perfect. Even natural roosts are seldom ideal.

Bats sometimes move into newly erected bat boxes within hours, but more often, bats may not take up residence for as much as one to two years. If your bat box is not occupied by the end of the second year, try moving it to a warmer or cooler location. One trick recommended is to acquire bat guano and treat the landing area of the box with it to mask the unnatural odors from construction (paint, caulk, the wood itself).
Outside dimensions of boxes should be about 1.5 feet tall and at least 12 inches wide with a 3-6”is landing area.
Roost partitions should be ¾” to 1”.
Ventilation slots should be ¼” to ½”
Half inch exterior grade plywood is best for fronts, backs and roofs, and roosting partitions.
1” board lumber is best for sides.
Prior to painting all seams should be caulked with latex caulk that remains flexible over time.
Paint exterior surfaces with two coats of exterior latex paint (dark brown, dark gray or dark green is best for Mid-Atlantic states).
Sun Exposure
Boxes should receive at least 6-7 hours of direct sun and be oriented southeast or southwest.

Easy 2’ x 2’ x ½” exterior grade (not pressure treated) plywood bat box cutting diagram.

Here's the layout on a 2' x 2' sheet of untreated plywood

Some detail of the measurements.

Marking grooves on the inside back of the box. These are for the bats to hold on to.

Cutting the grooves in to the board. I set the saw to less than 1/4". Cutting straight lines was NOT easy. The bats won't care and they are on the inside of the box where they can't be seen.

Edge on view of the grooves.

Applying caulk to hold the side spacers. The longer ones go down first. The shorter ones get caulked on top of the longer ones.

After stacking the front on top of the shorter strips, on top of the longer strips, on top of the back, nail the layers together from both front and back, with caulk in between each of the layers. After the caulk dries, Bevel the edge on a belt sander, planer or with a circular saw set to a 45 Degree angle.

I then attached the roof using caulk and the same finishing nails I used to attach the front and back.

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