Nestbox #1 (version 1)
(Intended for brushtails)
Nestbox #1 (version
(Intended for brushtails)
(Intended for ringtails)
Nest Box Design
I don't think the nesting habits of suburban brushtails are known
in great detail. We've seen, or heard about, them sleeping in various
unlikely and uncomfortable places such as rolled-up garage doors, or
the forks of trees. On the other hand, our comparatively safe and
comfortable possum boxes have often remained unused for months at a
stretch. This might be a result of the possums deliberately giving
one spot a rest to put predators off the scent, but I suspect that
our nestbox design is far from perfect.
There are a number of nestbox designs available on the web. Most
of them appear to be little more than modified bird nesting boxes. I
think that comparatively little science has gone into nestbox design
and we're a long way from having the ideal nestbox. The two boxes we
have constructed so far have been based on plans provided on the Ipswich
City Council web site (click on "+Habitat/Nest Boxes ";
the PDFs are at the bottom of the page) with a few modifications.
However, we've found that there's much more to nest boxes than simply
following a plan like the above one and if you're contemplating
putting up your own nest boxes, you might find the comments below
Although these notes are primarily about nestboxes for brushtail
possums, they will also be relevant to other species as well.
Plywood is probably the best material to use. It's very strong for
its weight, it stands up to weather very well without warping or
splitting and it's easy to work with. You must use exterior
grade plywood, which incorporates a waterproof adhesive - if the
plywood doesn't say what type it is it probably isn't suitable for
exterior use (although thick "structural" grade plywood
might be OK if painted). You can also use marine grade
plywood if you want, but this is more expensive and harder to get and
doesn't have any special advantages for this application. [Apparently
the difference between marine and exterior grade ply is in the choice
of timber, with the wood used in marine grade being free of holes and
splits so it won't leak when immersed in water. The adhesive used is
the same for both.]
I used 15mm exterior grade plywood for both boxes.
Different plans I've seen specify thicknesses from 12mm up to 20mm,
but I believe 15mm ply is a good choice. Thicker types are more
expensive, harder to find, and make the box heavier (which can be an
important point when you're balancing on top of a ladder trying to
attach it to a tree), whereas anything thinner is difficult join
without splitting the wood.
It's possible to make a possum box out of solid wood, and this
isn't a bad option if you have some scrap wood lying about and want
to save money, but you'll find it's more difficult to do and you'll
end up with a heavier, clunkier box. The Victorian DPI site
describing nestboxes for wildlife warns that solid wood may warp and
suggests that you "Arrange timber so that growth rings radiate
away from the centre of the box. Subsequent 'warping' will force the
box together rather than apart." A picture is worth a thousand
words here, and the illustrations on their site
make it clear what they mean.
Don't use treated pine. Some possums are fussy housekeepers
who lick the walls of their box clean, and we've also occasionally
seen them biting at their boxes apparently to remove splinters and
sharp edges, and therefore treated pine, which contains toxic
chemicals, is not a good material to use. Don't use craftwood,
particle board, laminex or similar composition timbers either; even
with painting these will disintegrate rapidly when it rains. This
type of timer product would be OK as the internal layer of a
double-walled box, but should never be exposed to the weather.
I would advise against using plastic or metal, even just for the
roof of the box (although a metal or plastic covering over a wooden
roof would be OK). Possums sleep during the day time when it's hot
and something without the insulating properties of wood can get
stifling. In fact, I have my suspicions that even a standard plywood
possum box would benefit from extra insulation [this is discussed
below under "Insulation/Temperature Control"]]. Consider
that possums naturally sleep in tree hollows, which are insulated by
many centimeters thickness of tree trunk.
The box should be fastened with screws rather than nails as these
are stronger and less likely to pop out under stress. You must use
screws suitable for exterior use, such as galvanised ones. I chose
ones intended for use with treated pine; these have a
Climacote™ coating which appears to be a very tough form of
enamel rather than conventional galvanising. I used size 8-10 x 57mm
countersunk screws for assembling the sides and bottom and 8-10 x
25mm for attaching other items such as climbing rails. Possum boxes
can apparently be assembled using glue in addition to screws, but I
don't think this is necessary. A properly constructed box will hold
together perfectly well without glue (in fact, the first possum box
we made survived a fall of over 4 meters from a tree without damage),
and I don't see the benefit of running the risk (albeit a minor one)
of using an adhesive which may be toxic or give off a smell that
could deter possums. If you really want to use glue, I would
recommend PVA woodworking adhesive (e.g. Aquadhere), as this is
relatively non-toxic and odour-free. I wouldn't use building adhesive
(e.g. Liquid Nails).
Left: Screws for assembling box
Right: Screws for attaching box to tree
We initially didn't paint our boxes and they stood up to all sorts
of weather for nearly four years without any problems. The wood faded
to a greyish colour which to some extent made the boxes blend in to
the natural colours of the garden. I think possum boxes constructed
from exterior grade plywood could safely be left unpainted if
When we refurbished the first possum box, we decided to paint it.
This was partly done to pretty it up, partly in the hope this would
make it cooler in hot weather, and partly because extra protection
from the elements wouldn't hurt. If you've got a neat orderly garden,
painting your box(es) to match your colour scheme is highly
recommended - why not make them a nice feature of the garden, rather
than something that needs to be hidden away ? I've seen possum boxes
painted a dark green, and I'm not too much in favour of this. The
dark shade chosen often contrasts with the natural colour of the
surrounding foliage and, rather than camouflaging it, makes the thing
stand out even more. Also dark colours will make the box hotter
inside if it's exposed to sunlight. We painted our box a colour
called Poncho, which is an off-white. This matches the house and also
goes with the off-white colour of the tree to which it is
Only paint the outside of the box. The inside doesn't need it,
and, as with adhesive, it might be toxic or offputting to the
The plans we used recommended that a brushtail box should be 350mm
wide x 350mm deep x 500mm high (interior dimensions). Our second box
was intended for ringtails and was 200mm x 200mm x 450mm.
I believe these dimensions are far from ideal. Our experience
is that the brushtails actually prefer the considerably smaller
"ringtail" box. Even our biggest brushtail, Olaf, would
always prefer the smaller box, despite the fact that his body filled
almost half of it. Ringtails, on the other hand, steadfastly refused
to visit either box.
We've read that possums prefer to squeeze into the tightest space
they can manage, presumably in order to exclude larger predators,
and this seems to be born out by our observations.
It's possible that brushtail box dimensions quoted were in fact
intended for southern brushtails. It seems that the further south you
go, the bigger the possums get, with Tasmanian brushtails being
gigantic fearsome things almost twice the size of our Queensland
If I had to recommend the dimensions for a brushtail nestbox, I'd
probably go with those specified on a leaflet from the University of
Ballarat, which suggests: 300mm wide x 250mm deep x 510mm high
(interior dimensions). It's also much easier to position a camera in
a deeper, narrower box like this.
Our boxes, in common with most designs, are of the
"vertical" type (i.e. with the longest dimension vertical),
however the Australian
Nestbox Company claims various advantages for a horizontal
orientation. This is one area of box design that needs more
I can't really comment on the suitability of different box shapes
except to note that the classic vertical type has the advantage
that a box camera mounted at the top of the box can see the
The diameter of the entrance hole is said to be a very important
parameter in nestbox design. For the first box we built, the plans
recommend a 120mm diameter entrance hole. Elsewhere, hole sizes of
up to 150mm were suggested. 120mm looked a little small to me, so I
used 150mm instead. This was probably a mistake since the second
(ringtail) box we made with a 100mm hole was preferred by the
Early in 2008 I fitted a collar around the hole in the larger box,
reducing the size to 110mm, and since that time the box has been used
more than formerly, although it still remains less popular than the
I think a hole 100-120mm diameter would be a safe size for
brushtails. If you were putting up a number of boxes, it wouldn't
hurt to use a number of different hole sizes. On one hand, a mother
plumped up with pouch young might need a larger hole (and possibly
also larger box), on the other, a recently independent baby possum
might prefer a smaller one.
The original design had an entry hole in the front of the box,
i.e. on the side opposite to the tree. I think this is a hangover
from the bird-box history of the design, and isn't ideal for possums.
We built our first box this way, but in this case, branches from a
nearby tree came alongside the box, making it easier for possums to
enter and exit. Our second box had a hole in the side adjacent to
the tree trunk, which is a better option.
If you're making a box for smaller species like sugar gliders, it
might even be preferable to have the hole on the side of the box
against the tree. [Obviously the box would need to be mounted
so that it stands a few inches away from the trunk to allow access to
the hole.] One site mentioned that sugar gliders prefer hollows
where the entrance is concealed from view.
Roof of Box
The top of the box should be hinged so that you can open it up
when you need to. Some designs call for the roof of the box to be
fixed in place permanently, but I believe this is a bad idea. You
might need to clean out ant or wasp nests if they decide to take over
the box (a common problem), and it might be necessary to remove a
sick or injured possum.
We used a strip of standard piano hinge along the back. This is
cheap and easy to work with, but has the disadvantage that it rusts
after a couple of years out in the weather. The ideal material would
be stainless steel piano hinge but this is more expensive. Probably
ordinary brass or galvanised hinges would work just as well. Some
designs recommend using a strip of inner-tube rubber for a hinge on
the basis that it's cheap and waterproof. I'm not sure how long this
type would last when exposed to sun and rain; it's claimed to
hold up very well.
On the opposite side to the hinge, you should put some sort of
catch or fastener to prevent the lid from flying open in strong
Some designs recommend a sloping roof to allow rain water to run
off more easily. This is probably not a bad idea, although it makes
construction a little more difficult. For what it's worth, both of
our boxes have flat roofs, and we haven't had any problems with
rainwater accumulating or running back into the box.
It's not essential, but I'd recommend that the box incorporate a
baffle. This is basically a fascia board (i.e. flap of wood
hanging down vertically from the roof) positioned like a visor in
front of the entrance hole. Its function is to screen the hole so
that it's not possible to look directly into the hole from
horizontally in front of the box. The use of a baffle has been
suggested to prevent Indian Mynahs nesting in the box (apparently
they won't nest inside if they can't fly directly in). The baffle
also makes the interior of the box darker and more appealing to
possums, as well as keeping out wind and rain. Our second box was
fitted with a baffle - this can be clearly seen in the photos - and
this is one possible reason why the possums prefer this box.
Possible disadvantages of a baffle are that it might make the box
hotter in warm weather and that it prevents possums from entering the
box from above. For this reason it's essential to fix one or more
rungs under the hole to allow them to climb up from below. Although
only a single rung is shown in the photo of box #2, I ended up adding
another two rungs underneath it to form a little ladder
A compromise is to use a partial baffle (i.e. one that only partly
hides the hole). If you don't have an Indian Mynah problem, this is
probably the best solution.
Floor of Box
The floor of the box should fit inside the walls and be
fastened with screws going horizontally (as opposed to the walls
sitting on top of the floor with screws vertical). This is a stronger
method of construction and also looks neater.
It is normal to drill a drain-hole of about 1/4 inch diameter (5
mm or so, it isn't critical) in each corner of the box floor to allow
any water that enters the box to drain out. We've never had a problem
with rain entering a box (they seem to stay dry in even the fiercest
of storms), however a few times we've had to pour water into a box to
shift ant nests.
Inside the Box
Most designs suggest you should fix wire mesh inside of the box to
allow young possums to climb in and out easily. Something like this
is required, because the concave plywood surface of the interior of
the box is too smooth for possums to climb. Wire mesh, however, may
not be the ideal material. Sometimes it appeared as if baby possums
were getting their claws caught behind the mesh while playing
(although we never witnessed a possum having serious problems with
this). Also, all the sharp ends of the mesh have to be bent back to
prevent them from projecting into the box, which is a bit tedious to
do. If you use galvanised wire mash (as we did), it will corrode
over time and this can't be healthy for possums who decide to lick
the wire (and we've seen them do this).
When we rebuilt the first box, we removed the wire and replaced it
by a series of wooden rungs fixed to the side of the box like the
rungs of a ladder. I think this is a better solution than wire.
You could also use wooden dowels, or a piece of board with
horizontal grooves cut in it with a router.
Take care to avoid splinters and the projecting ends of screws on
the inside of the box. Baby possums fling themselves around inside
the box with great abandon (see the Cocoa Leaping movie to see what they
get up to) and could easily be injured. It's true possums are hardy
creatures and often have to sleep in much more hostile places, but
then you often see possums with various injuries. If you manage to
put a screw in crooked and the end projects, probably the best thing
to do is to replace it with a shorter one, and sand off any
With brushtails, I don't believe it's necessary to place wood
shavings, leaves, or other nesting material in the box. Brushtails
are generally quite happy to sleep in a bare box. Occasionally we've
seen them take in leaves, but the reason for this is unknown because
they don't ever sleep on them. One theory we have is that mother
possums might take leaves into the box for their babies to play with;
a few times we say baby Cocoa playing with leaves brought in by
Ringtails and sugar gliders, on the other hand, do build nests,
and there seems to be some evidence that sugar gliders appreciate a
bed of shredded paper. Even so, I don't think it hurts to provide
unfurnished accommodation, since there's nothing to stop possums from
bringing in their own bedding.
I'm not sure whether anyone has studied the thermal
characteristics of tree hollows, but they are likely to be very
different to those of a relatively thin-walled box in the open air.
In the Bywong
Community Sugar Glider Project they built sugar slider boxes with
60 mm thick walls consisting of inner and outer wood layers, with
foam insulation in between. The intention was to emulate the
insulation provided by a natural tree hollow. The gliders apparently
like these boxes, but the site mentions gliders occasionally sleeping
outside of the box on very hot days, so the thermal characteristics
of this type of box might sill not be perfect.
It's possible brushtail possums may be more hardy than sugar
gliders, but they are by no means insensitive to temperature. We've
observed possums in our boxes and below 25° C they curl up into
balls to conserve heat. Much above this and they tend to lie on their
backs with their legs outstretched (often in quite amusing poses).
Once, on a very hot day, a possum (shown below) spent the afternoon
with the upper part of his body outside of his box. He would
periodically lick his forearms and hold them out in an attempt to
cool them in the breeze. It looked like he was very
Queek finding it a bit too hot in his box.
When this photo was taken, the temperature (measured in the
shade at the base of the tree) was 39.5° C.
We don't know whether this behaviour is normal in the wild or
whether our box was too hot. The baffle probably blocks the wind and
keeps the box hotter than it would otherwise be, and there's also a
camera inside which puts out about half a Watt of heat as well. On
the other hand, our boxes are well below the canopy and shaded for
the entire day. I'd hate to think how hot one of those dark green
boxes up the top of a gum tree gets when exposed to the direct sun
In the absence of any hard data I can only make some vague waffly
recommendations regarding box temperature control:
Site the box in a sheltered location. Ideally, shaded from the
sun in summer and protected from the wind and rain in winter. This
might not be achievable in practice, but at least try to keep it
shaded from the sun (especially midday and afternoon sun), and use a
baffle if there's a danger of driving wind and rain.
Although baffles might contribute to heat problems, I am still
generally in favour of them. You can see in the photo above that
Queek is still fairly well hidden from view by the baffle. Without
this, a possum might be open to attack by birds while craning out of
the box. Birds will harass possums caught out in the daylight. (In
2006 we saw this happen to Cocoa. The birds in question were
currawongs and noisy miners; I think a currawong could do a lot of
damage to a possum if it wanted to.) A shorter baffle than the one
shown might, however, be better as it could still provide protection
while interfering less with the air flow.
By all means try insulating the box if you can; it can't hurt.
Painting the box a light colour may also help, especially if it's
going to be exposed to direct sunlight.
Take into account heat generated by box cameras. A small CMOS
camera puts out little heat. A large CCD camera with built-in web
server might put out a considerable amount. If necessary, it might be
desirable to mount the camera outside of the box (but shielded from
the elements by some sort of cover), with the lens looking in through
In very hot climates, it might be worth incorporating some
extra ventilation into the box. I'm thinking along the lines of a
small opening near the bottom protected by some type of louvers to
keep out light and rain. I suspect that tree hollows might naturally
be ventilated in a similar way by a draft coming through fissures in
the heart wood.
Nestbox Company suggests that horizontal nestboxes have better
air flow on hot days.
Attaching the Box to a Tree
It is recommended to attach possum boxes at a minimum height of
4 metres above ground level (measuring from ground level to the
bottom of the box). When you're up a ladder, you'll find that this
seems very high indeed and you'll be tempted to fix the box much
lower. Certainly you shouldn't risk life and limb for the sake of a
possum box, but on the other hand, a box that's too low is either not
going to be used, or will expose its inhabitants to unnecessary
risks. Take care and use your common sense here. Use a ladder that's
the right length, place it on level ground (use a spade to level the
soil if necessary), and tie the top securely to the tree trunk with
rope. You'll be up the ladder for quite a while, so it's worth taking
the time to make everything secure. Having a second person hold the
ladder while you're working is not recommended because of the
danger of accidentally dropping stuff onto them.
For what it's worth, boxes 1 and 2 were initially 4.2 and 4.1 m
respectively above ground level. After it was replaced, the new box 1
was positioned 5 m above ground level. You probably don't need to go
this high, but I'd think that anything under 3 metres would be
The box should be positioned as far as possible in the shade and
with the entrance hole sheltered from prevailing winds (this is less
of a problem if you fit a baffle over the hole). Most importantly,
the hole should face roughly south-east (one place said that 100°
true was the optimal direction), and at all costs avoid facing it
west. I believe the logic is that possums like to sneak out of the
box as soon as possible after it gets dark, and when the sun is
setting the west side of the box will be illuminated while the
east is in shadow.
Actually fixing the box to the tree is a more difficult task than
you might think and something that requires careful consideration.
Trees are rarely completely even and vertical, and when you add the
constraints of box height and orientation, you'll often end up having
to fix the box in a very awkward spot. Also, it's very much
preferable to have the box mounted level - the possums probably won't
mind if it's leaning at an odd angle, but you'll find that it looks
very slovenly to the human eye, and if the box is in a visible
location you'll regret it every time you look at it. Wooden shims
located behind the box can be used to even it up and are worth the
effort to use. It might also be necessary to shim the box so that it
stands out from the tree in order to allow for the top of the box to
It's best to attach the box to the tree using screws. Nails can
be pushed out of the tree when it grows, and any sort of rope or
chain around the tree runs the risk of ring-barking it. According to
our local tree-surgeon, screws damage the tree less than any other
method and hold very securely because the tree callouses around the
screw, locking it in place. According to our tree-surgeon, the
weakest point of a screw attachment is the portion of the screw
immediately outside the trunk of the tree, which is in danger of
rusting. You should therefore always use coated or galvanised
screws. The original design showed two screws being used to mount the
box. Considering the size and weight of our boxes, this seemed
grossly insufficient. In the end, we used a total of six 14
gauge x 100mm long Bugle Head screws (shown above) for each box. It is necessary to pre-drill
holes for screws of this size.
We initially attached the first box by simply screwing through the
back of the box into the tree. This was difficult to do at the time
and was also the main cause of the box eventually falling out of the
tree. Owing to the difficulties we had with the first box, we
attached the second box via a separate back plate (described below),
and when we reattached the first box after the fall, we also used a
separate mounting frame.
I think that attaching a box like this (i.e. in such a way as to
make it easily removable) is a very useful feature, but unfortunately
something that rarely seems to be taken into account with nest box
designs,. We have found that this approach has the following
It might be necessary to paint or repair or modify the box
(e.g. to add a camera) and this is much easier and safer to do on the
work bench than up a tree.
It's much easier and safer to attach a mounting plate or
frame to the tree first and then later slot the box into place, than
it is to attach a whole heavy box in one go.
The screws going into the tree are the most vulnerable part of
the assembly because they are subjected to stresses from the growing
tree and may also corrode. If the box can be removed, it makes it
much easier to inspect these screws and to loosen, tighten or
replace them as required.
Australia Zoo recommend that the least traumatic way to take a
sick or injured possum to the vet is to wait until it goes into the
box, and then remove the entire box from the tree and use this to
transport the possum. We've never had to do this, but it certainly
seems a safer and less stressful method than dragging the possum out
and throwing it into a sack.
What is needed is a simple way to solidly attach a possum box to a
tree, but also to have it quickly and easily removable. Neither of my
two designs quite achieved this (they both fell down when it came to
the "simple" part), but they're worth considering as a
starting point. The design used for box 2 is probably preferable
because it's simpler and requires fewer special parts, however it's
only useful for attaching a relatively narrow box onto a straight
tree. This design consists of a back-board permanently attached to
the tree, with the box attached to the back-board by use of four
lift-off hinges. To prevent the possibility of the box lifting off
the hinges during high winds, and also for added rigidity, an angle
bracket was placed on the back-board underneath the box and attached
to the box by two cup-head bolts. Again, a picture is worth a
Box and back-board shown separated
Box installed in tree
To remove the box, we undo the two nuts on the cup-head bolts and
lift the box off the back-plate. This method works well and is very
secure. On the other hand, it was a tedious process to align all of
the hinges well enough so that the box could be easily slid on and
off, and a simpler method of attachment would be preferable.
The refurbished box 1 used a more sophisticated mounting frame in
place of the simple back plate. The method used is documented in the
Box 1 Replacement section below.
Installing a camera in your possum box adds significantly to the
cost and difficulty of the project, but we found it to be well worth
the effort. Checking a box from the top of a ladder is something
you're only going to want to do occasionally, and if the possums
aren't visiting regularly, you might not ever know if the box is
being used. And if your visit does happen to coincide with
that of a possum you'll discover that brushtails really don't
appreciate being woken up. We've found that the ability to look into
the box at any time, and also to record what's happening in there,
without disturbing anything, has been really helpful.
We placed a Swann "Day/Night Camera" in each possum box.
This was one of the lowest cost cameras available at the time, and is
much more suitable for the application than many more expensive
models. It is about the size of a box of matches and has infra-red
LEDs which allow it to be used in complete darkness. These cameras
have proved to be very reliable, with both having been running
continuously for nearly three years at the time of writing. These
cameras have the (relatively slight) disadvantage of a narrower than
ideal field of view and also the image quality could be better.
This is the camera placed in our second possum box. The strip of
wood above the camera was added to prevent possums from bumping the
camera when entering and leaving the box.
Nest Box Camera
Given that new technology is appearing every day, it might be
possible that you'll find a better camera out there if you look. You
should consider the following points when choosing a camera:
1) Check the minimum light level it will work at. You need one that
says 0 Lux (i.e. total darkness) and this means it will incorporate
infra-red LEDs to provide (invisible) illumination. If the camera
claims it's suitable for nighttime use, but the fine print mentions a
minimum light level of 1 or 2 Lux, it's probably not suitable. 1 Lux
is about the intensity of moonlight, and your box will often be
darker than this. [Although a fair amount of light leaks into a box
in the day time, a lot of the action happens when possums enter or
leave the box, which happens during the hours of darkness.] If
possible, check the type of infrared LEDs used, since some types emit
a dull red glow in addition to the infrared, and this is undesirable.
2) CCD cameras are said to give better quality images at low light
than CMOS cameras, but are more expensive and use more power (which
means they run hotter, which could raise temperatures in your possum
box). Our camera was a CMOS one, but it's possible that CCD ones
might now be available for a reasonable price. Don't expect to be
able to find a camera (even a CCD one) which will operate in colour
mode at low light. Even if the camera says it's a colour one, it'll
still switch to black-and-white in night mode.
3) Consider the angle of view of the camera lens. This is
52° for our cameras, which is a bit narrower than we'd like. Some
cameras have 90° angle lenses, which would be much preferable. Be
a little wary of fitting replacement lenses; I've heard that in some
cases a replacement lens will prevent a camera from being used in
night-mode (I assume it blocks the infra-red in some way), despite
being suitable in all other respects.
4) Some cameras don't support audio. Ours had a built-in
microphone and we found this to be useful on occasions; for instance,
it alerted us to the problem with Queek's eye when we heard him
emitting little shrieks of pain/anger when he was in the box.
5) Our cameras have analogue audio and video outputs, which
are connected into the A/V input of a VCR. This is a simple and
low-cost arrangement which requires no special technical knowledge to
set up. Other cameras such as webcams are available which use USB or
ethernet instead. These types currently seem to be less suitable. USB
cameras are limited by the length of USB you can use, which I think
is around 5 m, and would be inadequate in almost all cases. Ethernet
cameras usually incorporate their own video server are theoretically
very good (especially if the camera uses Power Over Ethernet, because
then you only need a single Cat 5 cable to hook it up) but the only
cameras of this type I've seen so far have been very expensive.
6) It might be possible to get a PCB camera (i.e. the
electronics are on a naked Printed Circuit Board, not enclosed in any
sort of housing) cheaply, but without modifications, these aren't
suitable for possum cameras. Possums have been seen to sniff, lick
and even box the cameras and geckos will sometimes be attracted to
the heat given off by a camera. Trying to save a few dollars by using
an inadequately protected camera is not recommended. The camera
doesn't need to be waterproof or anything special, it just needs to
Most of the difficulty and annoyance related to installing a
possum box camera is caused by the need to bring a cable back from
the camera. The cable supplied with the Day/Night Camera didn't look
suitable for use outdoors. Cables for exterior use need to have UV
stabilised insulation, or else they'll go brittle in the sunlight and
they also need to be physically strong. We ran our cable inside a
mixture of 20mm solid and 25mm flexible PVC electrical conduit. When
I replaced the first possum box, I replaced some of the 20mm conduit
with 25mm because of the difficult of coaxing the relatively bulky
connectors on the end of the cable through the conduit.
I think that using 25mm conduit from the start would pay for
itself in terms of reducing the frustration involved, and I'd also
recommend limiting the amount of flexible conduit you use as far as
possible; the ridges on this stuff make it really difficult to get
You'll find that in addition to conduit, you'll also require a
surprising quantity of miscellaneous fittings (elbows, saddles,
junction boxes etc.) to make a good installation, but it's worth the
time to do it properly. It's usually best to buy this sort of stuff
from your local electrical supplier (e.g. Ideal Electrical or
Haymans) rather than a normal hardware store because they've
generally got lower prices and a better range. And, just to note;
conduit saddles sometimes come with nails for fixing them in place.
When using saddles to attach conduit to a tree, do yourself a favour
and replace the nails with screws. I initially used nails and the
tree pushed them out after a short period.
Although our cameras came with 20m of cable supplied, we needed to
add another 18m extension cable to reach the camera in the back yard.
It seems the cable supplied with these cameras is selected for
smallest size and lowest cost rather than the best performance
because this length of cable degraded the quality of the picture
noticeably. I'd suggest that if you need a long cable run (i.e.
longer than the cable supplied with the camera) and want the best
possible pictures, you should make your own cable using proper
coaxial cable (Single-shielded RG-59U is said to be the best choice
here, apparently it works even better than the more expensive
quad-shielded RG-6U recommended for digital TV, because it provides
better shielding at lower frequencies. Most types of RG-59U coax are
tough enough to be used outdoors with a protective conduit.) for the
video signal. Probably shielded audio cable would be OK for the power
Our first possum box was installed on 19/2/2005. On 11/12/2008,
after nearly 4 years of use, it fell out of its tree. I've documented
the process of repairing, improving and replacing the box below. I've
found it easier to do it this way than to try to incorporate this
information into the possum box notes above.
This photo was taken in September 2008, three months before the
box fell. You can see that after 3 1/2 years out in the weather it's
holding up well. The wood of the box is still in very good condition,
with only minor water staining. Although not visible in the photo,
the roof of the box was badly water stained, especially on the top,
but not otherwise damaged. The item that has suffered the most is the
piano hinge on the left, which is fairly rusted, but even this is
still holding together and would be good for many more years.
In the large version of the photo, you can just barely see four
light-coloured indentations on the back wall of the box. These were
where the mounting screws were pulled into the wood as described in
the next picture.
Some other things to notice in the photo:
- The black object at the bottom left is the camera. This is bolted
to a curtain rail clip, which is clipped over the side of the box and
can easily be adjusted or removed.
- The wire mesh on the front of the box is intended to help
possums, especially babies, enter and leave the box. This has
corroded somewhat over the years and I feel the dangers from possibly
toxic corrosion products outweigh the advantages. This mesh was later
- You can see a wooden collar around the entrance hole. This was
added simply to correct the problem that the box was initially built
with too large a hole. There is no need for such a collar if
you cut your hole to the correct size in the first place.
- The leaves in the box were carried in by possums for
unknown reasons. They are not used as bedding; the possums
prefer to sleep on the plain wood and push the leaves to one
This is what the box looked like after the fall. The roof of the
box had been torn off but the box itself was undamaged, despite
having fallen over 4 meters. At first sight the screws attaching the
box to the tree look rusted through, however under closer examination
the surface of the metal is merely tarnished and what appears to be
loose and rusted metal is in fact rotted wood adhering to the screw.
What had happened is that tree grew out around the screws, pushing
the box away from the tree but trapping the screws in place. In
effect the screws were drawn into the tree. This placed the screws
under enormous tension. The two screws at the top eventually broke.
The one on the bottom left pulled through two thicknesses of plywood
and remained in the tree. Another two screws at the bottom of the box
(not visible in this picture) also pulled through the back of the
The lessons to be learnt here are that the method of attachment
needs some flexibility to allow for growth of the tree, and that
periodic inspection of boxes is needed to head off problems. I
think that even inspecting the boxes every couple of years would
A closeup of some of the mounting screws. You can see that they
haven't been weakened by rusting, but have simply broken under the
strain. Part of the problem may be that, even with pre-drilled holes
(a drill bit of a little over 5mm was used), it took a lot of force
to get the screws into the tough wood of the tree and this would have
placed them under considerable strain to begin with.
Although I ended up using different screws to replace the box,
this type (14g 100mm bugle head, with Zincalloy™ coating) look
like they would be quite adequate and hold up for many years if used
This is the box after refurbishment. The main body of the box is
essentially unchanged; we merely sanded down the wood and painted it
(on the outside only). We used Wattyl Solaguard paint. The light
colour ("Poncho" from the Wattyl i.d range) was chosen
partly in the hope that it will keep box cooler in hot weather, and
partly because it matches the colour of the house. There is an extra
rail on the right hand side of the box to allow possums to enter the
box more easily. A new roof was constructed. This is slightly larger
than the previous roof and overhangs the box on all sides. On the
previous box, the roof did not overhang on the side with the hinge,
and this may have contributed towards the rusting of the hinge.
The roof is hinged with piano hinge on the right-hand side (the
hinge is just visible in the large photo), and only opens about 90
degrees. The hinge was sprayed with cold galvanising before
installation for increased rust protection. Fascia boards were used
on the front and left sides on the roof for additional protection
against the weather. I didn't go to the extent of extending the
fascia down to form a baffle completely covering the entry hole; this
was partly because it would have added even more weight to an already
heavy box, and partly because it would have made it move difficult
for possums to enter the box from above.
Inside the box (not visible), the corroded galvanised iron
climbing mesh was removed and replaced by a ladder-like arrangement
of three wooden rungs.
Instead of attaching directly to the tree, the new box is
removable by the use of stirrups which slot over a frame that
attaches to the tree. The stirrups were made from strips of 20 mm x 3
mm mild steel bar. After bending to shape, these were cleaned and
sprayed with cold galvanising before attaching to the box. Attachment
is by 4 x 1 inch long by 1/4 inch diameter galvanised cup-head bolts
at each end. The bolt heads on the inside of the box are covered by
strips of wood to protect the possums from the metal if it heats up
during hot weather, and also to prevent them from licking the
galvanised coating. The current resident of the box, Queek, is
particularly fond of licking it all over, so we've avoided any paint,
glue or exposed metal on the inside.
Just visible under the fascia board at the top is a catch used to
ensure the box lid stays closed in high winds.
This is the frame before it was attached to the tree. The long
bolts on the right are 130mm long M8 (i.e. 8 mm dia) coach bolts,
which are used to attach the frame to the tree. The thick cup-like
grey washers on these bolts are a soft rubber material intended for
use on polycarbonate roofing and are used to give some flexibility to
allow for growth of the tree. These washers are also used between the
horizontal rails of the framework and the angle brackets to give
As with the stirrups, all metalwork has been sprayed with cold
galvanising; I bought a can of the stuff, so I thought I might as
well use it. The wooden part of the frame is made from second-hand
pieces of hardwood (probably redgum).
You can see that the construction of the frame allows the wooden
sections to pivot about a vertical axis. Also the slots in the
horizontal rails allow the bottom and top of each wooden section to
be adjusted in a left/right direction independently. In other words,
there's a lot of freedom to adjust it to fit an irregular tree
This shows the frame in relation to the box. Detached...
... and attached.
When the box was eventually attached to the tree, a large
cable tie was strapped around the upper rail/stirrup to prevent
the box from lifting off if, for instance, it was struck by a
branch during a storm.
Here is the framework bolted to the tree. Even on this relatively
straight section of trunk an extra block of wood had to be inserted
behind the frame at the top left to even it up. It actually took
quite a bit of fiddling around to ensure that the top and bottom
rails ended up level and parallel. You will notice that the top rail
is standing further out from the tree than the bottom one. This will
cause the box to tilt forward slightly and was done deliberately; it
promotes runoff of rain from the roof and also prevents the lid of
the box from hitting the tree when opened.
The wood of the tree, which I believe is a flooded gum (E.
grandis) was very tough and it was necessary to drill holes for
the mounting bolts. I used a 6 mm dia spade bit for this.
The dark patches on the tree trunk immediately below the frame are
where the previous box had been attached. The callousing in this
area made the trunk so uneven that it was necessary to mount the box
higher up the tree. The previous box was 4.2 meters above ground
level; the new box is closer to 5 m.
You will notice the top of the ladder is tied to the tree with
rope. This is an important safety precaution. Another piece of
rope is looped over a higher up branch and hangs down to the left,
this was used to hold the frame up while attaching it to the tree,
and was later also used for lifting the box into place, as it was far
too heavy and awkward to carry up the ladder.
Five meters is a long way up and this is why you want to secure
the ladder to the tree with rope. I also found it very helpful to
hang any large tools I needed from ropes. You can probably see a
cordless drill dangling behind the ladder.
Heights are dangerous, but not if you use your common sense. Plan
it properly, make everything secure and take your time. If something
is too difficult to do on the top of a ladder (e.g. because you only
have one free hand), work out a different way to do it.
This shows the box finally in place on the tree. The camera flash
makes the box look lighter than it does in reality.
The box was hoisted into place using a rope tied through the hole
in the front of the box. This was a safe method because the box
didn't have to be carried up the ladder and there was never any
danger of it falling, however this was less convenient than it could
have been because, with the lid open, the box dangled at an odd angle
and was difficult to slot over the supports. In future, it would be
worth looking at different ways of lifting the box; perhaps some sort
of sling could be looped around the box, or perhaps one or more
lifting eyes could be attached to the box.
And this is the box with the camera connected up. 25 mm electrical
conduit was used to protect the cable. This proved much easier to
thread the cable through than the 20 mm conduit I used last time.
At the time this photo was taken there was actually a possum
(Queek) sleeping in the box.