This Instructable will show you how to make a cage trap that can be remotely activated. This is ideal for people who practice trap-neuter-release (TNR) to control feral cat populations.

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Feral cat colonies are groups of wild, undomesticated cats. Some feral cats and their colonies are a nuisance to restaurants or other businesses. For this reason, some colonies are killed or trapped and euthanized. This is inhumane. TNR is a humane and effective way to control feral cat populations while allowing the cats to live out their lives.

However it can be difficult to efficiently trap every cat in a colony for spaying and neutering - sometimes the process takes months. One of the obstacles is trapping unwanted cats or other animals, which is not uncommon. A traditional plate-trigger cage trap offers no control over which animals are trapped. To overcome this, introduce the R/C Cage Trap, which allows the user to activate the trap only when the right cat enters:

Step 1: Materials and First Step

To make the R/C Cage Trap, you'll need:

A cage trap with plate-trigger
R/C car with steering
Stiff wire
Cable ties
Common household tools
Dremel or drill (optional)

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Garage sales are a great way to find a cheap R/C car. I searched for two weeks and didn't find one, so I bought one at Target that was on sale, and it came with a 10% discount for having absolutely useless drive wheels. I sometimes see cage traps at yard sales as well.

The first step is to carefully take apart the R/C car and extract the circuitry and the servo motor that controls the steering. My car was cheap and, after undoing a few screws, I was able to take everything apart by hand. A Dremel could be invaluable for this step. Be sure to maintain the integrity of the circuits and the steering mechanism. Save everything else for other awesome projects.

Step 2: Attach the Circuitry and Trigger

First I did what I could to protect the electronics by reattaching a flimsy black cover that came with the car (Pic 1). Mine slipped into place well enough, but I'd consider hot gluing it. Then I drilled holes into the circuitry/battery case (Pic 2). This will make it easier to tie it to the trap. Next I estimated where the trigger would need to be and attached the circuitry/batteries to the cage with cable ties (Pic 3).

Next comes the steering mechanism (trigger). I spaced the trigger far enough away from the trap door so it wouldn't interfere with the door closing, but otherwise the placement isn't crucial. My steering mechanism's motor fit nicely between the cage bars (Pic 4), which means that it won't budge easily. This will help ensure that the trap is consistant and reliable; the trigger must be completely stationary. Then I snugged it in place with several 12" cable ties (Pic 5). Make sure they're nice and tight, but avoid cracking the plastic casing.

Try it out! Make sure the steering mechanism can shift left and right when you use the remote control.

Step 3: Modify the Latch

The next thing I did was modify the latch. Normally, when a cat steps on the plate-trigger (Pic1), a metal rod is pulled which undoes the latch and sends the cage door slamming down (Pic 2). You'll need to deactivate the plate by detaching the metal rod that connects the plate-trigger to the latch (Pic 3).

Next, you'll need to make your own rod to attach the steering mechanism (the new trigger) to the latch. I found a stiff piece of wire and bent it into a hook (Pic 4) and then attached it to the latch (Pic 5).

Finally, the last step, and possibly the most crucial aspect, is attaching the rod to the new trigger (Pic 6). The steering mechanism for your car may be different from mine, so I cannot give any specific instructions. However, I can offer this advice:

When adjusting the trigger sensitivity, I found that lengthening/shortening the rod was the easiest way.
You can adjust the sensitivity further by bending the latch hook (Pic 5).
When the trap is set, the trigger/steering mechanism should be pulled taught toward the trap's door.
You may also want to slightly bend the rod away from the cage so it doesn't rub against it when the trigger is activated.

Step 4: Make It Better

I feared that the R/C car I used would have poor range, so I wanted to maximize the distance of the user from the trap. To that end, I used some more stiff wire to hold up the floppy antenna. But I didn't want to attach it in a way so that it would always be sticking up all of the time, so I simply cut a groove into the side of the circuitry box that snugly holds my new antenna, but could be laid down when not in use.

What else would make this trap more effective or easier to make?

Step 5: Test It Again and Again

Yay, it's done!

Be sure to test the trap thoroughly before bringing it to the field. Try giving the trap a firm nudge - if the latch is too sensitive it may release when the cage is rocked, which is undesirable. You can avoid this by placing the trap on a sturdy and level surface, or by desensitizing the trigger.

I hope this Instructable will help many people efficiently perform TNR to humanely control feral cat populations. If you make one of these, please consider posting photos or a story of what you were able to accomplish.

Thanks, and happy trapping!