I have finally replaced Box 1.
|New Box 1 in tree - 25th Aug 2020|
The original box was first installed in 2005 and despite partial refurbishment in 2008 it was in poor condition.
|Old Box 1 prior to replacement - 17th Aug 2020|
It was held up by a single bolt but was actually more secure than it looks because the bolt and part of the frame had been engulfed by the tree and proved quite difficult to remove. The roof was degrading around the edges (there was a fascia board at the front which has fallen off entirely), but it was still protecting the interior. I suppose the box was still usable by possums, but they deserve better than this.
|Interior of old Box 1 prior to replacement - 17th Aug 2020|
The box camera was the last of the original Swann Day/Night cameras that I installed in the first two boxes. The picture was not great quality and owing to the angle of the box the camera kept getting knocked out of position.
The replacement box incorporates a number of new features.
I redesigned the mounting frame.
|Box 1 mounting frame - 23rd Aug 2020|
The point of having a mounting frame separate from the box is that it's much easier and safer to attach a relatively small and light frame to a tree and then haul the box up on a rope and clip it to the frame, than it is to somehow hold the box in place while fastening it directly to the tree. The new box weighs more than 14 kg and is attached to the tree over 5 m above ground level, so the process of getting it into the tree safely was something that had to be planned out carefully in advance.
The new mounting frame was welded out of 1" angle iron and bolted to the tree with four 8 mm stainless steel bolts. The frame is spaced out from the tree by using aluminium tubing which fits over the stems of the bolts.
The reason for spacing the frame out from the tree is that the tree (a flooded gum) is particularly enthusiastic about repairing any damage done to it. It considers a bolt going into the tree to be damage and it grows out around the bolt to try to engulf it. This is what caused the destruction of the previous frame.
By the way, the scar left in the tree by the previous frame just below the new frame looks a bit ugly but is not harmful to the tree. I have talked to an arborist about similar scars elsewhere on the tree (caused by branches from other trees rubbing on it etc.) and these are normal and not a problem unless there is fungus or other signs of infection.
Some gum tree branches were attached to the sides to make it easier for possums to enter the box.
The box was painted with Wattyl Solagard. I have used this on previous boxes and it holds up really well. I used a light colour (Colorbond Shale Gray). I strongly recommend using light colours on possum boxes that will be subject to direct sunlight. In the past, it seemed to be the rule that wildlife boxes were painted a really dark green. This is fine if the box is shaded (and if you get the option, it's better to install the box in a shaded location), but in full sunlight a dark colour makes the box unacceptably hot inside.
|Box 1 on table - 24th Aug 2020|
Looking inside you can see that it's more than just a simple box.
|Box 1 open - 24th Aug 2020|
The long black thing on the rear wall of the box is a temperature sensor. For the record, this is an AD592 temperature sensor with some added components to reduce the chance of damage from lightning surges. Last year, three of these sensors were destroyed by a nearby lighting strike.
The silver-grey box is the camera. This was built the same way as the Box 2 camera, but uses a slightly different camera board inside.
The issue - which I only discovered while testing this camera - was that the eBay drone cameras I had purchased actually had smaller image sensors than claimed. They said they were 1/3" but were actually more like 1/5". A smaller sensor means a lower quality image, but that isn't a problem for the box cameras where the image quality is limited by other factors. The problem in my case was that a smaller sensor size means a more restricted viewing angle.
I got away with this in Box 2, because this is a very narrow box (it was intended for ringtails and was made significantly smaller than the others), but the new Box 1 is much wider in proportion to its depth and the lens angle was barely enough to see the entire bottom of the box.
After some consideration, I pulled apart a pinhole camera that had been kept as a spare for the old Box 2 camera (until I realized that pinhole cameras work really badly in possum boxes) and was able to fit the board from this into the new camera. This has a 1/4" sensor, which is not ideal but I think it does well enough.
The interior of the box is an octagonal shape to more closely resemble a tree hollow. Box 7 is this shape and the possums look a lot more comfortable when curled up in it.
Climbing rungs made from small pieces of gum tree branch were attached to the inside walls (not visible in the photo above, but see the pictures at the end of this post). I had previously used strips of plywood for this purpose and in most cases just attached them under the entrance hole to aid possums getting in and out, but I had found that baby possums would use them for climbing practice and I think some actual branches will be easier and more fun for them to use.
The aluminium bar on the left is a prop to hold open the lid. The shape of the lid is such that it won't stay open by itself and if you're working on the box in a tree you don't have a free hand available to hold the lid open. A solution is to jam a stick or something under the lid to hold it open, but this is fiddly and annoying to do and if done wrong the lid can slam closed on you.
So I devised a prop. It's a piece of rectangular aluminium tubing fixed to the outside of the box with a pivot at the front. It fits over a tab screwed underneath the roof.
The black thing on the roof below the camera is exactly what it looks like; a fan. This is an experimental thing.
There have been studies which show that possum boxes get much hotter than natural tree hollows. Painting them a lighter colour helps, but only to an extent. I have noticed that when the temperature goes above about 35 C, possums in boxes start to get very uncomfortable. I have heard accounts of possums abandoning their boxes and seeking shelter in the shade at ground level during extra-hot spells. It is very dangerous for a possum to be at ground level during the day and a possum would only risk this if the temperature in the box was unbearable.
We have so far been spared the mega-heatwaves that most other places have suffered, but it's only a matter of time before one strikes here and I would like to do what I can to minimize stress on the wildlife. Some people mist their possums with water from a hand sprayer in the hot weather and this seems to be much appreciated, but this is not easily done with the boxes here, which are mostly around 5 m above ground level.
I am not sure to what extent a fan will help. Possums lick their wrists to cool themselves through evaporation and my idea is that having some air flow should help with this. But anyway, it's an experiment; if it doesn't work at least I'll know.
I have used an 80 mm square 12 V low-noise computer fan. This has been covered with some mesh I had left over from fixing a screen door. I don't think the light plastic fan blades will necessarily be hazardous to possums, but I'm more concerned about spiders taking up residence within the fan and I don't want it to catapult a hail of angry spiders at the possum when it starts up.
When possums are comfortable with using the box, I will wait for a hot day and try out the fan by turning it on (which can be done remotely) while observing the possum inside over the camera. If the fan proves a success it would be possible to control it automatically based on box temperature.
Here is a shot which shows the location of the box. It's on the South side of the tree and mostly shaded during the day, but does get some sun in the afternoon.
|New Box 1 in tree - 25th Aug 2020|
The box was not up long before the possums came to check it out; first was Rahmet and later Sasha and Wink visited. No possum has slept in the box yet.
|Rahmet visiting Box 1 - 25th Aug 2020|
|Sasha (top left) and Wink (bottom right) visiting Box 1 - 25th Aug 2020|