Should
You Bat-Proof your House?:
There is little reason to evict bats from buildings where they are
not causing a nuisance. However, bats should be prevented from
entering human living quarters and in some instances, noise or odours
from large colonies of bats can become a nuisance.
Before deciding, make sure that your fears
are not unwarranted!
Contrary to what you may have heard:
- Very few bats become rabid (less than half of 1 percent).
- Bat droppings in buildings usually are not a source of
Histoplasmosis.
- Bats are not filthy and will not infest homes with dangerous
parasites.
- Bats are not aggressive and will not attack people or pets.
- South African bats do not feed on blood. (Vampire bats, which do
feed on blood, live in Latin America.)
Please see notes on Bat
Phobia for more details!
Excluding bats from a dwelling is the only long-term control method
for bats who are a nuisance in a building.
When
to Exclude Bats
Never try to evict bats from their
roosting places during the following periods:
- In winter during hibernation. They won't be able to fly far to
find new roosts, cannot forage and due to exposure, will die.
- During the maternity period from middle September to the end of
December. This is when new babies are born and nursed by their
mothers. Babies can't fly and if you evict the adults, the babies
being trapped inside, will die and create an odour problem.
It is best to evict & implement exclusion methods in South
Africa between February and May.
Exclusion
& Eviction Methods
- Inspect your house for markings,
droppings or physical presence
A simple inspection of the outside of the building can be made to
determine whether bats are living in. Bats usually enter a building at
the roof/wall joint, under loose fascia boards, or through broken
vents or other cracks resulting from building deterioration. Bats can
crawl through openings as small as half a centimetre.
- Watch out for bats leaving their roosts
at dusk.
The bat watch should be started about 30 minutes before dusk.
Station enough people around the building so that the entire roof and
wall area can be kept under constant observation. If bats are present,
they will start leaving the building about dusk; the last bat should
come out of the building within one hour of the first bat. All bat
exit and entrance points should be noted, as well as the number of
bats. This procedure may take several evenings to accomplish, but it
is important to identify all bat holes.
If only one exit/entry hole is found in the course of the
inspection, it can be plugged as soon as the last bat leaves the roost
(hence the reason for counting the bats). If several holes are
identified, all but one of them should be plugged during the daytime.
Wait a day or two to give the bats a chance to get used to using the
last opening, then plug it as soon as the last bat has left in the
evening.
Bat-Proofing
Materials
1. One-Way
Valves
An excellent way to plug an entrance hole is to install a
bat-proofing valve. This device, which consists of a rigid base tube
with a pliable outer sleeve attached, is placed over the entrance
hole, allowing bats to exit the dwelling but not to
re-enter.
2. Using
'One-Way' Netting to Exclude Bats
Bats sometimes enter buildings through openings on smooth surfaces
of exterior walls or through louvers. In such cases, plastic or
lightweight, flexible netting with 0.4 cm mesh or smaller, should be
secured to the building along the top and sides of the opening to
allow bats to exit the building, but not return, as shown in the
diagram on the left.
After this has been done, watch to make sure the bats are able to
exit safely. If they do not appear to be exiting, or appear to be
having trouble doing so, make adjustments or add new valves as needed.
3.
Using PVC Pipes to Exclude Bats
There are a number of situations in which tubes work best as bat
exclusion devices.
Examples include openings used by bats on buildings constructed
from materials that do not create smooth exterior walls, such as those
found on brick or stone houses, and log cabins. Tubes also work best
for holes located at corners where walls meet and on horizontal
surfaces.
Exclusion tubes should have a 5 cm diameter and be approximately
25.4 cm in length.
Exclusion devices can be made from PVC pipe or flexible plastic
tubing. Use of a flexible plastic tube makes it easy to either squeeze
one end of the tube so that it fits into a crevice, or cut one end of
the tube into flaps that can be fit over an opening and stapled,
nailed, or taped to the building (see diagram). Bats are unable to
cling to the smooth surface of these tubes. Once the tube has been
inserted over the hole, a piece of light weight, clear plastic can be
taped around the end of the tube that projects to the outside (see
diagram) to further reduce the likelihood of bats re-entering, though
this is typically not necessary.
Problems
Bat-proofing has two potential drawbacks.
One is that exclusion can be stressful for a maternity colony. When
prevented from using their usual roost, the bats may move into a nearby
building, where they may be expelled again, or even exterminated. Also,
research has shown that displaced colonies will not relocate into
buildings that already house other maternity colonies. In other words,
an excluded colony cannot just move down the road into a barn or church
that already has bats. If a displaced colony cannot find a new roost, it
may leave the area. In fact, researchers have found that expelling bat
colonies can contribute to serious declines in local bat populations.
A second drawback is that homeowners may find it difficult to
bat-proof their home completely. Bats can crawl through cracks as small
as 0.5 - 1cm, so persistent bats may find a way to re-enter their former
roost.
Bat boxes can solve both of these problems because they provide
alternative roosting sites for maternity colonies. When constructed
properly, bat boxes can serve as suitable places for females to raise
their pups. With bat boxes, the bats get a safe roosting site outside
the home, while homeowners benefit from the bats' control of insects.
