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Frog-friendly backyard

Metro Toronto Zoo Bat Box Programme

Bats are the primary predators of night flying insects. Yet the most abundant species of mammal in Canada is losing habitat. It is preferable to leave bats in their traditional roosts, but by offering alternative housing in a bat box , we can learn what bats prefer as roosting sites and what their requirements are. The Bat Box Program is geared to helping people under stand that bats are an important component to our ecosystem. It is not meant to encourage people to evict bats from existing dwellings, but act as an alternative housing for those who decide to evict their bats. It is necessary to stress the importance of learning to live with bats.

When is the best time of year to install a bat box?
Because female bats require a warm, safe shelter for giving birth in May, bat boxes should be installed in March or early April. You could also build and install your bat box in late summer or fall for early occupancy the following spring.

Will the age or type of wood affect occupancy of my bat box?
Aged wood appears to affect timing, but not the probability of use. There is no evidence that bats prefer a particular type of wood.

Where should I install my bat box?
Generally, the higher the better. For practical purposes however, heights of 4-7 metres (12-15 ft) appear sufficient. You may install your bat box on either a pole, tree, or the side of a house, as long as exposure to sunlight is adequate. Installing a bat box on a southerly facing brick wall as opposed to a wooden wall, will increase heat absorption. It is important that your box be located away from dense woods or shrubbery, preferably along the edge of a woodlot or clearing, and be free of tree branches which act as flight obstacles. Protection from the wind in a valley, or on a hillside as opposed to a hilltop, is preferable. It should be kept in mind that exposure to sun is one of the most important criteria for determining use of bat boxes, and at least 5-6 hours of direct sunlight is required each day.

How much sunlight and heat are required?
Ideally one would install three houses with different exposures: South, East, and Southwest, as to provide the bats with an alternative refuge in case the temperature in a present dwelling becomes inhospitable.

Why might bats not use my bat house?
You may not have positioned the bat box so that it receives an adequate amount of heat and sunlight, or perhaps the box is too drafty, or lets in too much light through cracks. It may simply be that bats are not able to live in your neighborhood, due to a lack of an adequate water supply, pesticide use in the vicinity, or the absence of a suitable hibernating site or migratory route. Try a new design or location? Keep us informed of your successes and failures.

When can I inspect my bat box?
Use of your bat box should be obvious by the presence of droppings below the roost. If you wish to check for occupancy, simply shine a flashlight up into the bat box during the day, without touching or disturbing it in any other way. To deter mine actual numbers, count the bats as they emerge at dusk.

Can bats be introduced artificially into an area?
Bats have strong homing instincts, and once removed from an area against their own free will, attempt frantically to make their way back. For this reason, artificial introduction into a new bat house should not be attempted.

I have bats living in my attic and wish to keep them there. How can I clean this area safely?

It is best to clean in the fall, when the bats have moved out for the winter. Be sure to wear a surgical or painters mask, and once all of the fecal material has been removed, use a dilute bleach solution (1 part bleach: 10 parts water) to clean the area. Bat guano is a nutrient rich fertilizer, and may be used in your garden to enhance soil quality.

If I paint or stain my bat box, will it decrease the chance of occupancy?
No. New research indicates that stained or painted exteriors do not repel bats. In fact, bats living in cool climates like Canada, may show a significant preference for houses with an exterior either painted black or stained dark; dark colours will increase heat absorption. In warmer climates, a natural wood or light colored box may be appropriate to maximize heat reflection.

How to build a bat box . Contact: Friends of Bats at Metro Toronto Zoo for further information about bats or bat boxes.

How else might I provide a suitable home for bats?
Having a 1.5 meter (5') minimum clearing around your box keeps the area free from flight obstacles. Tacking mosquito netting or .65 cm. (1/4") hardware cloth inside the box gives the bats, especially young ones, a better roosting grip. Increasing the length of all dimensions, or adding vertical partitions 2-2.5 cm. (3/4"-1") apart within the box is recommended. It has been suggested that adding bat droppings or using wood taken from a known bat roost may provide an inviting odor, but there is no documented proof that this is the case.

Do I have to clean my bat box?
No. Most bat box designs have an open bottom, so droppings will fall through. If you choose a box design with an attic, you may open the hinged top after the bats have left for the year, and simply whisk the droppings down the centre hole.

For more information on building a bat box contact:
Friends of Bats
Metro Toronto Zoo
316A Old Finch Ave
Scarborough ON M1B 5K7

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