Building a Low Pressure, Humane, Animal Trap

I had a problem, I had a whole family of squirrels in my garage, I like squirrels- they are cute, and generally friendly. I don't like them in my garage.

I don't blame them for wanting to be in my garage, it is pretty awesome in there, but it is a problem; they chew on electrical wires, poop, and there is also no food sources in the garage. So they had to go.

I can borrow a commercial metal animal trap, but the issue is that I encountered right away was that the pressure plate in one of those requires a bit more force then a small squirrel. So I was quickly able to catch mommy squirrel, but none of her children. This is bad, now I have a bunch of baby squirrels in my garage, no food, and no way for them to get out.

I needed an animal trap that could be triggered by the minuscule weight of a baby squirrel, and hold them securely until I can release them.

Step 1: 1. Bill of Materials

To build this trap you will need:

Main body:
4x 2x2 cut to 1.2m
4x 2x2 cut to 35cm
2x board cut to 1.2m long, 35cm wide
2x Screen mesh 1.2m long 40cm wide
screening (cut to fit when complete.

Door:
1x board cut to 55x40cm
2x 2x2 cut to 30cm
2x 2x2 cut to 35cm
4x 1x2 cut to at least 20cm
small bungee cord

Teeter trigger
1x 2x2 cut to 1.2m long
2x 2x2 cut to 35cm
rope

Tools required:
Jig Saw
Drill
Hammer
Nail gun/staple gun
Brad nailer
round file

Consumables required:
Roofing nails
2in screws
3in nails
2in brad nails

Step 2: 2. Assemble Base Frame

At this point you will assemble two rectangular frames, be sure to pre-drill all holes, those 2x2s will not take a screw directly and the wood will split if you do so.

Step 3: 3. Form the Box

Attach the boards to the top and bottom of your frame, forming the box that will be the basis for the rest of your trap.

Step 4: 4. Attach Mesh Screens

Attach the mesh screen to the sides.

I used the roofing nails, as they slightly overlap the edges and hold everything well in place. You could use staples if you have them long enough, or put another 1x2 on top and screw that down (again be sure to pre-drill)

Step 5: 5. Put the Back On

Using the thin screening cut to shape for the back of the cage and attach, I used a mixture of roofing nails and staples to hold this in place (the staples into the plywood boards because they will not split it, the nails into the 2x2s)

Step 6: 6. Begin Construction of the Front Door

The front door is a 'guillotine' style- don't let that scare you, the idea is it closes when the animal is nowhere near the door itself, and the trigger mechanism takes a lot of the weight off the door, so while it shuts with some speed (somewhat slower then gravitational acceleration) it does not have a lot of force behind it.

Step 7: 7. Build Front Door

Make a cut into the front door to leave a 'notch' just at the top line of the trap when the door is closed. Make the exposed part of the notch slightly wider and taller then a 1x2.
This is where the lock will engage when the door drops

Step 8: 8. Build the Locking Mechanism

In order to hold the door down once it has closed some sort of locking mechanism is required, this simple setup is to carve a small notch into the back of a 1x2, in which a bungee cord will sit trying to push it forward against the door. When the door comes down the notch we put into it will become exposed and the lock will engage, you will need to pull it back in order to unlock the door.

Step 9: 9. Build the Teeter System

The teeter is basically just that, a teeter-totter that holds on one end the trigger mechanism, and on the other the door.

Take a single 1x2 and notch it.

Cut a larger then 1x2 hole in the top of the trap.

Build up 2 2x2s vertically from the trap, and place the .5in metal rod through them and the teeter bar.

Tie both ends of the teeter bar to the trigger and the door respectively.

Step 10: 10. Optional Improvements

While your sawing away at the back of the trap in order to put the trigger mechanisim, you might want to make a nice big lockable panel so that you can more easily place bait inside.

The trigger meachanisim as provided is very gentle, so the animal only needs to brush it in order to set it off, but it only covers part of the cage, tiny critters may go around it, so enclosing it in a screen while depressed will increase the surface area of contact that the animal may brush it from.

Alternatively placing a 'flap' pressure plate way at the front of the cage leaning up against the trigger mechanism should assure that sufficient force to dislodge it is created by even the smallest lightest critter by the time they get to the bait.

Finally you could build a 'reverse teeter' hooked up directly to the bait, basically, assure that if the weight of the bait changes negatively, the trap triggers. The downside to this is that the animal may be on its way out when the trap finally triggers, and getting the balance exact may be difficult, but it assures that if the animals has gone for the food it will trigger.

Carry handles would be nice as well, or you could reinforce the teeter mech so that you can carry it by that.

A 3d printed trigger notch, and rim- would really improve the sensitivity by assuring that you need far less lip to catch the mechanism then the rather coarse wood will allow for. Milled trigger mechanism would be similarly effective.

Similarly 3d printed, or bearing sliders on the door would make for a more smooth closure.