Bat pole

 

One nice thing about having a wood-lot is that when I get a yen to take on a project, I can walk out the door and harvest a 20' long pole.

This one is Black Locust and is 7" in diameter at the butt and 5" diameter at the top. Some back of envelope calcs suggest that it has a green-weight of about 250 pounds.

I muscled it to the fence that separate the wood-lot and the pasture and got the butt end of it a few feet into the pasture. Mrs ERJ lifted up the bottom of the fence while I tied the tow-strap to it and then dragged it with the truck.

It is not the straightest pole, but being Black Locust it should be durable. And the price was right.

My current plan is to make the bat-boxes based on interior dimensions of the storage boxes discussed HERE. They will be mounted with the long dimension vertical so the interior cavities will be 15-1/2" tall by 9" wide by 3/4".

I should be able to fit 4 cavities into it using either pallet wood or commercial 1-by for dividers. My target is to have the opening slots 0.75" or 19mm in Canadian even if the internal cavities are a bit larger. Narrow slots exclude more predators. I will not have safety netting below the box for the same reason, predators can perch on the netting.

There was an abandoned iron mine in northern Michigan that had been sealed off with hurricane fencing. The mine was used by thousands of bats and it was one of the prime places for them to hibernate during the winter.

The fencing was replaced after one of the biologists who was visiting observed multiple raccoons sitting on the fence and grabbing bats that flew to the fence and had to "walk through the holes" before resuming flight on the other side. The raccoons were grabbing the bats by the wings and biting off their heads-thorax and then discarding. The 2" mesh hurricane fence was replaced by welded concrete re-bar with openings large enough that the bats could fly through it.

Yes, I will put a metal collar around the pole but red squirrels are great jumpers and this will be in an orchard where trees might encroach on the pole and grow close enough to the pole for squirrels to make the jump. 

If I put the pole in the center of the Eaton Rapids orchard, there are ponds 1340' and 1400' away and a cattail marsh 1000' away. At The Property, if I put a pole in the middle of that orchard there is open water 700' away.

I wouldn't be surprised if bats find suitable cavities via echo-location.

General hints  (Source)

Virtually all kinds of bat houses were at least occasionally successful. But the best-used houses were:

• tightly constructed, caulked, and painted
• mounted 10 to 25 feet above ground on buildings or poles
• positioned to receive sun appropriate to local climates
• roosting chamber widths of ¾ to 1 inch
• sited within a quarter-mile of a stream, river, or lake
• located in areas where bats were already attempting to roost on or in buildings

Except in areas of extreme day-to-night changes, pairs of houses mounted back-to-back on poles in full sun, one facing southeast, the other northwest, are increasingly favored by America’s most experienced bat house users. Testing can pay big dividends.

In Florida, Ernie Stevens hung a bat house from a tree limb and attracted a nursery colony of 124 apparently desperate evening bats. When I convinced him to try mounting a pair of houses back-to-back on a pole in full sun, his original colony moved to the house facing northwest and expanded to over 300. These were joined by free-tailed bats in the warmer southeast-facing house. His resulting mixed colony included 800 bats!

In Louisiana, Bill Halloway began by mounting two houses on pine trees. No bats were attracted, so he moved them to a pole, mounted back-to-back. Bats promptly began moving in. Encouraged, he added another pair of larger houses on a pole, one black and one white, and ended up with a mixed nursery colony of 800 free-tailed and big brown bats, apparently due to a greater range of temperature options.