G4 Harp Trap
Assembly and Advice
Bat Conservation and Management
220 Old Stone House Road, Carlisle, Pennsylvania 17013
717.241.ABAT • 814.442.4246
www.batmanagement.com
The world's most refined bat trap.
Application
Adjusting a line in the
dark may result in a
loss if the operator is
overzealous. There are
four extra spare line
holders on board the
trap to make field repairs
quick and painless.
Harp
traps
are
primarily used as a low
maintenance solution
for
sampling
bat
swarms and emergences
at
natural
caves,
abandoned mines, and
other underground
structures. Secondary
uses include summer
sampling in conjunction
with conventional mist
nets and artificial roost
surveys. Bat trapping
solely for pest control
purposes is a misuse of
this device, is much less
efficient than a simple
“one-way exclusion
device”, and is illegal
in many states.
The “extra hole” at the
top of the headpiece
plate is large enough for
a carabiner, and enables
the entire contraption to
be hung from the top.
It's in the Bag
The catch bag is a
deceptively difficult
engineering problem,
as most bats are quite
crafty escape artists.
Our bag is made from
heavy
duty
clear
plastic, ungrippable
and easily cleaned.
The bag's sidewalls are
raised above the bottom
trap line bars, making it more difficult for bats
to escape out the sides should they land on the
Lower Line Bars. The Baffle Bar holds the all
important plastic baffle in the center of the bag,
thwarting flight. A narrow removable lining is a
roost platform. This is a layer of canvas with a
plastic overlay where the bats can rest and await
their fate comfortably instead of flailing about.
Held in place with Velcro, it is totally removable
and washable.
Trap anatomy
Composed of aluminum
with stainless hardware,
traps can be anodized
flat black (or end user
painted) for a big increase in stealthiness. Field
assembled with pins on rings (extras on board),
no tools required.
Each telescoping Upright features two lock
knobs for extra line tension security. A Leg
Mate, interchangeable among all trap models,
clamps onto the Uprights for those who wish to
stand the device up. The leg kit can remain on
the Uprights in storage, telescope to allow for
uneven ground, and can even change vertical
position on the Upright for ultimate versatility.
Moving the harp will not leave legs behind.
Stretch cords adds tension along the front and
back of the bag, decreasing the size of the potential
escape route and restricting flight further. The
bottom of the bag contains grommet drainholes
to help avoid unwanted swims.
The lines are held tight with individual stainless
screws. Simply loosen the screw, feed in the line
and tighten. The trap lines can be individually
tensioned. Besides the fact that we hate tying
knots, we wanted the option to use high strength
black spectra lines which are impossible to use
on comparative systems due to the material's low
stretch. Individual tensioning solves that.
2
Harp Trap Assembly and Advice
6
lower
line
bars
5
headpiece
5
Hello
Harp Trap.
2
2 legs
4
1Leg
moose ear
1
4
Mate
3
baffle bar
3
7
catch bag
1
Add Leg Mates
Disassemble the Leg Mates by completely
removing the thumbscrews. Position the Leg
Mate on the Uprights as shown and replace the
thumbscrews. Make sure thumbscrew side of
the Leg Mates is always on the inside (wing nut
side) of Upright.
Leg Mates can be put on the Uprights upside
down. If so, the legs will not support the trap.
Refer to Step 2 and ensure Leg Mates are
oriented correctly.
2
Add legs
Add legs to the Leg Mates and secure using
the stainless steel cotterless hitch pins that
are provided.
Many of the harp trap's joints are formed by
nesting tubes. The trap is machined with tight
tolerances and certain parts will seize if not
inserted or removed at the correct angles.
3
Add Baffle Bar
Place the clear plastic flight baffle over the
baffle bar. The baffle bar then connects the two
uprights forming the bottom frame of the trap
and allowing the device to now stand up.
4
Add Moose Ears
Add the moose ears to each upright using the
provided wing net.
4
Harp Trap Assembly and Advice
5
Add Headpiece
For the trap to function, the Lower Line Bars are removed from the Headpiece
and placed in the inner holes of the Moose Ears. Before the Headpiece can
be attached to the Uprights, the no-spin slots for the lower line rods must
match the corresponding slots in the Moose Ears.
No spin slots for
lower line bars
on Headpiece
and Moose Ears
must always
match. (Bars
removed for
clarity.)
Add the correctly orientated Headpiece to the tops of the Uprights. One
person can accomplish this easily first insert the hitch pins into the tops of
the Uprights. Next, place the Headpiece on the Uprights, resting temporarily
on top of the pins. With the Headpiece now supported, remove one pin on
an Upright and secure the Headpiece to the Upright. Repeat for the opposite
side.
Note: It is not necessary to pin the Headpiece to the Uprights during normal
use the trap, but is recommended anytime the trap will be hung.
Tear down tip: do this procedure in reverse to single-handedly remove the
Headpiece. Do not move the telescoping portion of the Upright after the
Headpiece is removed to aid in quick setup next time-- the holes will stay
aligned for the next setup.
First time (unstrung) setup; VERY IMPORTANT:
There are slight differences between the two Lower
(grooved) Line Bars. Before stringing the trap, make sure
the Lower Line Bars grooves match the corresponding
screws in the Upper Line Bars.
Line bar grooves are intentionally
offset. Make sure to match the set
before stringing the trap.
Harp Trap Assembly and Advice
5
6
Unroll Lower Line Bars
Remove a Lower Line Bar from the Headpiece, keeping
the pin handy in your hand or in a pocket.
Whichever hand is near the hitch pin end of the Lower
Line Bar is your "control hand".
Keep the control hand on the hitch pin end of the line
bar during unrolling (and rolling up for storage). By never
removing your hand from this end during setup or tear
down, lines on this end will never become wrapped the
wrong direction on the bar and become entangled.
The lines on the opposite end of the bar (especially the 6'
wide trap) are out of reach to maintain during assembly
or disassembly. The key to properly managing these lines
solo is to wind the Line Bar on a steep offset angle from
the Headpiece. By carefully watching the far end of the line
bar without removing your control hand, the lines should
not become entangled between setups.
Unrolling or winding up the line bars: always keep your
control hand on the hitch pin end of the bar.
Carefully watch the far
end to ensure lines roll
the same way...
It doesn't matter WHERE the lines wrap up...
as long as they are all in the same direction.
Never remove control hand
from lower line bar during
setup or tear down.
6
Harp Trap Assembly and Advice
7
Add Catch Bag
Before installing the catch bag, consider that a number of
bats will roost on the cloth baffle inside the bag. Therefore,
if setting the trap in a cave or mine, the roost baffle should
be in the front, where a technician can easily remove bats.
Install the catch bag only after the Lower Line Bars are in
place and properly tensioned.
Begin by installing the rear catch bag bar to the rear hole
in the Moose Ear using the hitch pins. Then carefully bring
the front bar forward under the trap. Carefully work the bag
ends around the sides of the trap. The bag will fit nicely
without pulling tightly. It is not necessary to remove the
support bars from the bag for storage.
Start bag assembly at the back, working to the front. Be
careful to work the bag around the trap bottom sides as
shown.
It recommended on the 6' trap to add the included 48''
stretch cord between the to the Moose Ears. This supports
the middle of the bag and may prevent a few bats from
escaping by flying straight up the bag center.
Use the telescoping legs to level the trap. The trap should
be nearly perfectly vertical from all views, otherwise the
frame may twist.
Add stretch cord across the bag front and back for extra
support on 6' traps.
Trap/bag front
Harp Trap Assembly and Advice
7
Stringing the Harp Trap
Common mono filament fishing line, 4# to 16# test
is generally used, and can be found at any sporting
goods store. Some researchers observe no difference in
capture rates when using heavier lines during swarms at
hibernacula entrances. Heavier lines are generally more
durable and are easier to thread, but will be harder to
stretch evenly. For summer trapping in forest situations the
user will probably choose the thinner end of the scale. We
suggest Stren 8# “low visibility green” as an all purpose
line for either the 6' or 3' traps.
Next take the line to the corresponding set screw on the
upper line bar. Wrap the line three times around the Upper
Line Bar, and under the flat washer.
Composite lines offer much higher strength to weight.
Fireline brand is made of spectra material and offers 20#
strength in a traditional 6# line diameter, and comes in
black. This line may be used on the 3' Cave Catcher trap,
but is difficult to stretch properly on 6' wide models.
Set up the trap without the catch bag. Do not extend the
Uprights fully as they will need an inch or two to allow for
stretching over time. String the harp one side at a time,
beginning on the ends and working towards the middle.
For stringing Forest Strainers, it is convenient to use a
stepladder.
Add a degree of tension to the line before securing with
the set screw. The amount of tension you add should be
consistent with all additional lines. Use enough torque on
the set screw to hold the line, but do not overtighten the
line as the washer may compress the line and shorten its
life span. Experiment with the first line to get a feel for
tensioning the line and tightening the set screws.
A stainless steel #8-32 x 3/8'' set screw, flat washer, and
split ring lock washer should be placed in each threaded
hole in the two stationary upper trap rods.
Knotting the lower line bar
Before stringing the trap, refer to step 5 on page 5 and
ensure the line bars are properly matched.
The Clinch Knot is a strong, reliable connection that resists
slippage and premature failures. This knot can be used to
fix the line to a groove in the Lower Line Bar. The knot’s
unique double wrap design and ease of tying consistently
yields a strong, dependable connection. Add a third wrap
to add more strength to the line if necessary.
1 - Run end of line
around the rod in the
groove at least twice.
2 - Loop around
standing part of line
5 or 6 times. Thread
tag end between the
bar and the coils as
shown.
8
Harp Trap Assembly and Advice
Advice, suggestions, and tips.
Rigging
Orient the trap so that the catch bag roost is towards the
observer side of the hibernacula. To funnel bats towards
the trap, thin plastic sheeting is usually placed behind the
trap (on the inside of the mine) and a hole is custom cut
out for the harp. Duct tape can be used to attach plastic
to the harp trap if necessary. Extreme care must be made
so that "pockets of plastic" do not form in the sheeting.
Bats may fumble into a shallow "plastic pit" of sorts and
become entrapped. This is especially dangerous in wet
areas or during rain events where pools will form in the
plastic.
For small hibernacula entrance work, legs are sometimes
not needed. The trap is readily hung from holes provided
in the Headpiece. Hang the trap from overhanging roots,
shrubs, rock projections, etc. At managed sites the trap
can be hung directly on gates. The trap can be rigged to
mine walls and ceilings sometimes by pounding long nails
into cracks. Care and responsibility is necessary when
working at natural caves due to the delicate nature of
these resources. Most states have cave protection laws
which deter vandalism and any modification of the site.
Using formations for rigging is never acceptable, and
floors with formations must also be completely avoided.
Pounding objects into cracks in rocks which upon closer
inspection turn out to be near 10,000 year old petroglyphs
is considered very poor form and could be subject to very
high fines. A missed nail during take down may also rust
over historic signatures or formations. For many cave
entrances, roping projections or using a Leg Mate is
recommended.
The temporary semi-closure of the entrance will have very
little effect on airflow. However, for extended projects
where sites are relentlessly trapped, it is recommended
that made-to-fit screens be installed to eliminate any
chance of airflow disruption. At sites with significant
airflow, cut long vertical slits in the plastic to reduce air
pressure.
Trapping
Leg Mates are surprisingly versatile in that not only do the
legs telescope, but the Leg Mate itself can be repositioned
vertically on an Upright to compensate for very uneven
ground.
Unlike mist nets, harp traps require very little attention
when open for business. Provided that lights are off and
there is no smoking, bats do not seem to mind if people
are present nearby. Infrared illuminators will not deter bat
activity. Traps should be checked occasionally to ensure
bats are not escaping the catch bag or being trapped
in bundles of extra plastic. Very rarely a
bat's wing may become caught where
the a line wraps around the lower line
bar. Bats in the catch bag are easy prey
for opportunistic owls, cats, weasels,
raccoons, and the like. In particular
weasels will jump in and out of the
catch bag while owls will patiently perch
on the bag rods and/or ram the trap and
breaking lines. Any site with a history of
this kind of activity should be monitored
continuously.
Why bother with legs if you can hang the trap?
While all cave bats generally play nice
with each other, larger species such
as the big brown (Eptesicus fuscus)
might be better pulled out of the batch
of smaller bats sooner rather than
later. Forest bats should also not share
quarters with cave bat species. At large
swarming sites, place bats in a temporary
holding cage or even a 5-gallon bucket
to process away from the trap site and
reduce disturbance from lights. Do not
Harp Trap Assembly and Advice
9
allow more than 75 bats to become piled up inside the
catch bag at once as there may be a danger of suffocation.
Process more frequently or gain additional staff to avoid
dangerous backlogs of bats. If more than one or two bats
come out of the catch bag slightly bloodied, this is a sure
sign of infrequent processing.
Extra holes in the Headpiece?
On the underside of the top trap rod there are four
threaded holes in a row. These are on board storage
slots for extra set screws and washers.
The catch bag contains drain holes in case of a brief rain
event. The drain holes do not replace the responsibility
of careful monitoring during wet weather.
There are two or three non-threaded holes straight through
the top trap rod. These holes are intended for spare 1/
4'' cotterless hitch pins. Prevent loss of spare pins by
inserting them into the trap, then placing a few wraps of
tape around the protruding ends.
De rigging
Lost hitch pins or wing nuts?
Keep in mind bats will be desperate to avoid the trap. You
will observe them crawling along cave passage walls and
ceiling at the edges of the plastic or screens in search of a
bypass. They may even be found on the ground. Careful
attention must be given when disassembling plastic to
avoid wrapping up bats. Bats like to hide in the catch bag,
and it is best to get into the habit of inspecting it several
times before storing.
Don't panic. The only pins that are really critical to the trap
system in most cases are the legs and catch bag. Once
assembled, wing nuts are not necessary either. These
items can be found locally at most large hardware stores
in the "speciality fastener" section.
Several traps make sampling vertical pit entrances a snap.
Cleaning and maintaining
the trap system
The trap is constructed of aluminum, stainless steel, and
plastic. The catch bag may be wiped down with a mild
detergent such as Ivory soap and then hosed off when
needed. To restore the aluminum to new condition, scrub
the parts with a green Scotchbrite pad and dish soap. If
pins do not disengage smoothly for your tastes, simply drill
the hole slightly larger using a 17/64 drill bit. To remove a
frozen part or to keep parts disengaging smoothly, apply
a very small amount of WD-40 household lubricant.
Packing the trap
Pack the trap by first placing all parts inside the storage
bag except the Catch Bag and Headpiece. Protect the
lines from damage by placing the Headpiece on top of
or inside the Catch Bag, separating it from other parts
and equipment.
You do not need to remove the bag supports from the
catch bag. It is not necessary to remove the baffle from
the center bar for storage.
10
Harp Trap Assembly and Advice
Large harp traps sometimes completely
fill cave and mine entrances requiring no
additional setup.
There is no elegant way to trap a low,
wide entrance with an irregular floor.
Bats will see your trap and swirl
in front of the cave/mine entrance.
Use this to your advantage by
erecting a 2nd trap as seen here
and double or triple your catch
numbers.
Harp Trap Assembly and Advice
11