Tuesday, February 10, 2015

Kitten-proofing mousetraps

Update: This is the Mk.1, which has some flaws which I since identified. Be sure to check out my post on the Mk.II, it will save you some time and effort.

Mousetraps and kittens don't mix. Kittens - or cats for that matter - are curiosity incarnate, and many of the baits we regularly use in mousetraps smell delicious to cats. If your cat gets into your mousetrap, the best case is a broken paw, the worst case is a smashed skull - with all the unpleasant things in between. Now, we have had1 a kitten, and we had a mouse in the larder.

Do not despair, cat lovers, I didn't put my sweet purr machines in danger - and I'd like to share my briliant concept with you, so your cats can purr in safety too. Behold - the kitten-proof mousetrap!

Yeees, the mouse trap is in the tube, got it in one. Here's how to build your own.

1. Measure your cat's arm.

Yes, I'm dead serious. Holes and tubes are even more interesting to cats than anything else, especially if they smell like delicious bacon might be in there, so it has to be long enough and then some, because cats have a strong urge to probe such tubes with their paws. Yes, that could defeat the purpose of the whole project if the tube is too short! 

NOTE: Do I need to mention that if you have more than one cat, you have to measure all of them and use the greatest arm length? Don't guess, cats vary a lot in stance and build. You'd be amazed to find that a 5 lb kitty can actually have a longer arm than a 14 lb tom.

Here's how to measure correctly:

Your cat's arm is built exactly like yours, it has an elbow, a wrist and fingers. Because cats walk on their fingertips basically the wrist is somewhere in the lower third of the long part of the paw. The wrist is the thing cats sometimes fold under their body when sitting. (See monorail cat pictures for details). Above that comes the elbow. Above that the shoulder.

The best way to get your cat's arm length is to stretch the elbow with two fingers and your thumb  (don't use excessive force!) and quickly measure from the shoulder to the tips of the (by now probably extended) claws. Make sure your cat is in a good mood, be quick about it and have some bactine or iodine ready just in case. Cats move their arms into this pose when they stretch, so they are not too averse to letting you do it, provided you are polite, quick about it and there's the prospect of some treats.

You will probably have some error in your measurements - try to err on the generous side.

2. Measure your mouse trap.

Mouse traps vary widely in shape and size, so get the measurements of yours lest you complete the project to find out your trap won't work in the tube. The measurements you want are:

  • Width of the trap
  • Total length of the trap
  • greatest height of the trap during the action. Hold the kill bar in place straight up, place the trigger wire across where it would be, measure from the ground. Don't forget the thickness of the base board!

3. Cut some cardboard.

The right material is 3-5 mm corrugated cardboard. It should be strong enough to stand up to some cat attention and mouse teeth, but not so strong you can't get the folds in properly. If possible, cut so the corrugation is parallel to the short side for added stability.

Here's the formulas for the measurements:

Lenghth: (2 * L(paws) + L(mousetrap))*1.1

Note here that I added 10% extra safety margin, because it's amazing how long cats can make themselves if they want something just - out - of - their - reach - almost - got - it...

Width:  5 * (n* 1.1) ,where n is the greater of the width of your mousetrap and the maximum height during action.
Again I added 10% margin, because the folds take up some room and the whole construction gets too tight otherwise.

4. Fold the cardboard.

Corrugated cardboard isn't easy to fold. If you aren't among the few luckies who have a sheet metal bending machine, try the following technique:
 first mark the folds

 then carve in the folds. Use the edge of a two-by-four to hammer in the folds with a rubber hammer (or any other if you're not concerned about the wood)

last, bend the folds carefully. Make sure the bend really follows the pre-cut folds.

repeat for all the other folds. Bend them well to make sure it assembles into a tube flawlessly later. Pro tip: break the folds backward to increase the flexibility.

5. Place the mousetrap

Measure for the middle of the tube you assembled and place the mouse trap there. I like to attach it with velcro spots for easier cleaning/loading etc.

6. Place some velcro spots or strips to hold the tube closed. 

Don't be too sparing with those, that cardboard retains an amazing amount of spring tension and an opened tube defeats its purpose.

Now load the trap and carefully close the tube. There - you're set!

Update: When I designed this, I forgot that mouse traps are kinda directional weapons. Stuff some kitchen tissue paper into the end of the tube that  faces the back side of the mouse trap, or else modify it into a Mk.II which corrects that problem.

1(different story there, not a nice one, gonna spare you)

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