Introduction: Rat Trap Mods: Catch Mice and Wireless Monitoring

Picture of Rat Trap Mods: Catch Mice and Wireless Monitoring

I spent over a year monitoring and modifying rat traps in my crawlspace with the aid of an infrared night vision security camera (Hikvision DS-2CD2032-I). The modified traps are so sensitive that they can even catch shrews which are much smaller than mice. The camera was set to record high resolution video at 30fps and send email alerts when motion was detected. Video footage was reviewed and each time a trap failed I developed a mod to prevent future failures. After the last mod (rear-guards) I have had 100% success rate on the last 3 mice and 1 rat. With modified traps I've caught 60+ mice, 4 rats, 2 shrews and 1 chipmunk.

You may be wondering why anyone would use a rat trap to catch mice? If you have holes big enough for rats, mice can enter too. Mice will likely steal the bait from a non-modified rat trap without setting it off, then you can't catch anything. Also if a rat is injured by a mouse trap it can make it 'trap shy' and it will avoid all traps.

The picture is the box containing the trap and the window alarm attached to the outside.

Step 1: Shrew

Picture of Shrew

A shrew is about 1/5 the weight of a mouse.

Step 2: Alarm Console

Picture of Alarm Console

A red light corresponding to the trap turns red when it fires. To setup a new sensor, switch the console switch to 'Install', then hold down the test button on the new sensor. Switch the console to 'Run 1' for Led lights only, or 'Run 2' for Led lights and a beep when the sensors are triggered.

Step 3: Rat Trap Parts

Picture of Rat Trap Parts

Step 4: Safety Tips

Rodents carry disease so you should wear disposable gloves when handling the traps. Also wear a breathing protector to protect from airborne disease and dust if you are setting the traps in an insulated area.

Modified rat traps can go off from wiggling or bumping them and they have enough power to hurt fingers, so care must be taken when handling them. The traps convert the potential energy of the spring into kinetic energy of the hammer. If you are handling a loaded trap always approach and release the trap from the back. If the trap goes off the hammer will hit your hand before it develops speed. I recommend wearing a gardening glove on your left hand until you get used to setting them.

After setting the trap use a stick to push it gently into the box. The boxed trap should be gently placed with the back to a wall, immovable object or fist sized rock. The reason for this is that when viewed in slow motion (see the Slow Mo Guys video) the traps move backwards ~1/4" as the hammer moves forward, but then the whole trap moves forward after the hammer hits the platform. The 1/4" could make the trap miss a rat if it jumps back.

Step 5: ​Hold-down Bar Pinch

Picture of ​Hold-down Bar Pinch

Pinch the loop at the end of the hold-down bar with needle nose pliers. Insert a small nail or screw in the loop before pinching to prevent the hole from closing too much. This will allow the hammer to be bowed out more in the next step.

Step 6: Hold-Down Bar Pinch Before and After

Picture of Hold-Down Bar Pinch Before and After

The left-side is before and right-side is after the pinch.

Step 7: ​Hammer Bow #1

Picture of ​Hammer Bow #1

Use 2 pairs of pliers and a screw driver to bow out the hammer. In Hammer Bow #2, the top-half is before the mod and the bottom-half is after.The hammer should be bowed until it almost touches the loop of the hold-down bar when the trap is set, note the ~1mm gap in Hammer Bow #3. Bend a little at a time and test, final measurement from the spring to the outside of the hammer will be around ~3-3/16" or ~81mm. Bowing out the hammer puts most of the force from the spring on the hinge end of the hold-down bar, which unloads the catch making the trap more sensitive.

Step 8: Hammer Bow #2

Picture of Hammer Bow #2

The top-half is before the mod and the bottom-half is after.

Step 9: Hammer Bow #3

Picture of Hammer Bow #3

Note the ~1mm gap between the hammer and the pinch.

Step 10: ​Rear Guards #1 and Top Shield

Picture of ​Rear Guards #1 and Top Shield

Rear Guards

Rear guards prevent rodents from going around to the back of the trap. The guards are curved pieces of plastic that fold down when the trap fires. They are made out of a 16oz/0.5L soda bottle. Cut a 3/4" ring out of a soda bottle, then cut it in half. Staple one half to the platform on each side of the catch. Masking tape has been placed on the plastic to make it visible in the pictures and the tape has been marked with a black pen where the staples are holding down the plastic strips.

Top Shield

Cover the front, top and sides of the platform with packaging tape, it will make the trap easy to clean and re-use.

Step 11: ​Rear Guards #2

Picture of ​Rear Guards #2

The guards fold down when the trap fires.

Step 12: Catch Bend Front

Picture of Catch Bend Front

Bending up the front of the catch that holds the bait encourages feeding from the front. Use 2 pairs of pliers to bend the catch. Use one pliers to hold the middle of the catch and the second pliers to bend the front half up.

Step 13: Catch Bend Side

Picture of Catch Bend Side

With the trap NOT set, push up on the hold-down bar with a finger (see picture) and engage it with the hook on the catch. Bend the catch to the side a few degrees at a time until the catch is barely holding the hold-down bar. If the hold-down bar is slipping out too easily, bend it back a little.

Step 14: Bait

Picture of Bait

Mesh from fruit bags forces the rodent to bite and claw at the bait, usually setting off the trap within 20 seconds. This bait is so effective, I get multiple rodents without adding or changing bait. Zip tie a small (grape sized) wad of a mesh fruit bag to the catch, see picture. Trim the mesh so it is only accessible from the front. Put a pea size dab of peanut butter in the mesh, pushing it into the mesh. I've seen a few mice ignore 3-4 week old bait so I recommend changing bait every 3 weeks. Use an old shoe to trigger the trap, cut the zip tie with dikes and re-bait.

Step 15: Box

Picture of Box

Putting the trap in a box prevents rodents from entering from the back or sides, makes the trap easier to place and allows easy mounting of the wireless alert transmitter. The box should only have an opening in the front, I had a rat climb over the side of an earlier version with an open top. The box inside dimensions should be 3.5" wide, 7" tall, 8" deep.

Step 16: Wireless Alerts #1

Picture of Wireless Alerts #1

The X-10 wireless alarm system can monitor up to 16 traps. Window sensors are used on each trap. The orientation on the platform is critical, the arrow must be pointed towards the back. Drill small holes and zip tie the sensor to the platform as in the picture, the double stick tape will not hold it when the trap fires. DO NOT mount with the provided mounting holes, they would make the arrow point up or down and the sensor will not work. The wired part of the sensor should be attached towards the bottom on the back of the box with double stick tape and the electronics taped to the top of the box. In my tests the orientation of the wired half of the sensor did not matter.

A solid red light corresponding to the number of the trap goes on the console when a trap is triggered and it can also be set to beep. The traps fly out of the box even with a rat which triggers the window sensor. The X-10 can dial phone numbers if you connect it to a phone line which would be good for monitoring traps at a remote location. I have 3 monitored traps, 1 in the garage, 1 under the hot tub and 1 in the crawl space. The console is about 100 feet away from the furthest trap and has worked well in ~3 months of testing.

If you get occasional blinking red lights on the console, it means a trap hasn't checked in for 4 hours. If this happens try putting an 18" straight copper wire underneath the electronics module on top of the box, parallel to the length of the module. Some wire will hang off the front and back of the box. If the wire isn't stiff enough, use a long stick or plastic tube to keep it straight. The wire works as a passive helper antenna, people on the x10 forums say it extends the range by 2 or 3 times. My blinking red lights were solved using this method. I've tested a trap that had a corresponding blinking light and the light changed to solid. If there are problems with a trap in below freezing temperatures try lithium AA batteries because they work better at low temperatures. Battery life is at least 3 months with Kirkland Signature AA cells.

Parts Needed for Wireless Monitoring

Wireless Alerting System (buy 1) X-10 Voice Dialer Security Console (Base Only) - Model PS561 Ebay or Amazon $30 to $80

X-10 Security Door/Window Sensor DS10A (buy 1 for each trap) Ebay or Amazon $6 to $10

Tip: Put window sensors on your garage door and on your freezer to alert if either are left open.

Step 17: Wireless Alerts #2

Picture of Wireless Alerts #2

The wired part of the sensor.

Step 18: Wireless Alerts #3

Picture of Wireless Alerts #3

Electronics taped to the top of the box.

Step 19: Tips for Sealing Up Holes and Cracks

Picture of Tips for Sealing Up Holes and Cracks

Mice are incredible climbers. The picture is a low resolution email alert from my security camera, the mouse is climbing straight up a standard 25 year-old foundation wall.

Mice can crawl through a hole smaller than a dime. Here's a video of a mouse going through a 17.5mm hole, a dime is 17.91mm.

Tips For Sealing Up Holes and Cracks

I found multiple cracks and holes where the rodents were entering, the last hole was sealed a few months ago and I've been rodent free since! Go around your home and look where wires and pipes enter, any hole or gap bigger than a dime needs to be sealed with wire mesh. If you have a drain in your crawlspace make sure it is covered with wire mesh. Use a stiff wire such as a coat-hanger to probe for gaps between the siding and the foundation all around your house. My house had a 15 foot section with a gap big enough for mice to climb the outside foundation wall and through the gap in the siding. Sections of a 1in x 1in board were screwed in the inside to prevent entry.

Garage Entry

Do not allow rodents in your garage! Avoid leaving the door open or cracked dusk to dawn. There are many unsealed holes for pipes and wires in the garage which allow them to go anywhere in your house. Seal any holes or cracks leading into the garage that are larger than a dime.

Trees and Shrubs

Trim back any trees and shrubs that could allow rodents to get on your roof.


Rodents can crawl across wires to gain entry. Guards can be placed on them.

Step 20: The Last Hole!

Picture of The Last Hole!

The last hole discovered was chewed by rats straight through a healthy 2" x 8"! It was hidden by the deck and repaired by stapling wire mesh over the hole.

Step 21: Modified Rat Trap Vs. ?

Below are my opinions on other traps.

Black Plastic Rat Trap

I tested a name brand black plastic claw rat trap. Mice will rarely trip them. I recorded mice sitting on the trigger eating all the peanut butter. I had some success with partially triggering the trap by moving the trigger down about 75% with a stick. It's a hassle and still didn't work well against mice. The mechanism is hard to get to so they would be difficult to modify. The x10 window sensors would work great with them, they go flying forward when triggered.

Green Poison Blocks

I used poison for years. The rodents die in random places, eventually one died in a wall. The smell was so awful, I will never use poison again, with the exception of trap shy rodents. FYI, the smell goes away after about a month.

Electric Trap

I hear these traps work great though I have not tested one. Electric traps are expensive and there is no easy way to add wireless alerts to them. Unless you are checking the traps daily you may have an odor and mess to clean up or need to throw away an expensive trap.

Humane Catch and Release Trap

I have not tried one. Unless you are checking the traps frequently (daily?) the rodent could suffer a cruel death from thirst or starvation. Also there is the risk of releasing a diseased animal into a healthy population, thus spreading disease. The X10 wireless window sensor could be added to these traps which would make them more humane by facilitating an earlier release.

Glue Trap

Glue Traps are not humane, some areas even ban them.

Mouse Trap

I skipped mouse traps because I knew I had rats and mice. If you only have mice, using mouse traps would be a easier way to go. The same wireless alerting system and other mods should work for improving mouse traps too.

5 Gallon Bucket Trap

Not tried. These are a great way to deal with a hoard of mice. I haven't seen info on their effectiveness against rats, maybe rats are too smart? Rats have been known to tread water for DAYS, so imo these traps are not humane for rats. The bucket is big, so there are limited locations it can be used and I can't think of a good way to monitor/alert besides a security camera.

Ultrasonic Noise Maker

Not tried. A credible website says that they work for a while but the rodents adapt to them. If someone has evidence that these work please post. A good test would be to monitor an infested area before and after with a night vision security camera.

Step 22: Feedback Request

Big Rats?

I was only able to test on the four medium-sized rats that entered my crawlspace. If you have big rats I'd like to know how the traps perform. Someone else has come up with a mod to make the trap more powerful by placing a spacer under the spring where it rests on the platform which creates a larger force. I wonder if adding some weight to the hammer could increase the power too. This could possibly be tested by measuring the distance the hammer goes through a lump of clay before and after the mod.


I'd also like stats on how many successful catches vs misses you have with a modified trap.


Swansong (author)2018-01-02

I hope they catch them all and you don't have to deal with them anymore, they can be such a nuicance!

About This Instructable




More by kelpchex:Rat Trap Mods: Catch Mice and Wireless Monitoring
Add instructable to: