Trapping Tips - The T-Rex/Tomcat Rat Snap-Trap

I’ve been using a combination of DOC traps and snap-traps to control small predators since I began trapping 5 years ago. I use a variety of snap-traps, but the model that I have the most experience with is the T-Rex (which I’m abbreviating to TR). In addition to ship rats and brown/Norway rats, I’ve killed a number of weasels, and several small hedgehogs with the TR.

Like all traps, the TR has its strengths and weaknesses. I think that the TR has the potential to be a valuable weapon in trappers’ arsenals, so I’m writing this post to give trappers that haven’t used TRs before, a thorough review of the trap, and to pass on some advice and tips. If you have experience using the T-Rex/Tomcat, and have something to add, please post replies.


The largest predators that I’ve killed using TRs are brown/Norway rats. For those of you that don’t have the pleasure of trapping this rat species, a large brown rat grows to nearly twice the size and weight of a large ship rat, weighing up to half a kilo.

I can’t state, objectively, how powerful TRs are, so I have to rely on anecdotal evidence. Several experienced trappers that had never used a TR, were impressed by its power.

I do know how much damage a TR can do to a thumb when you aren’t being careful, though. A blue thumbnail for a month and bleeding, rough scrapes where the teeth hit, certainly got my attention!

The Teeth
TR’s teeth are very effective, in my experience, at holding predators in place, usually by the neck. Using snap-traps without teeth, rats have managed to escape on a handful of occasions, with tufts of fur left behind. I have yet to find any evidence, however, of a predator escaping TR teeth.

When I first started using TRs, I wanted to find out if the teeth were effective. I found that it takes a lot of effort to pull predators free, and I couldn’t do it without doing a lot of damage to their bodies. Scavengers haven’t managed to pull predators free, including small rodents, just eating the parts of the carcass that are exposed.

Snap-traps with teeth are especially important if you’re using vertical traps. Predators are more likely to escape from traps without teeth, due to their smooth fur, the pull of their weight, and their movements.

Predators that are able to escape a trap without teeth, will suffer injuries from both the trap and from the fall to the ground. Predators that receive fatal injuries will, I assume, take longer to die than if they were secured to the base of a trap by the kill-bar, and those that receive non-fatal injuries have the potential to live in pain for some time. An additional concern is the potential to increase the number of trap wary predators within a population, because predators that survive their injuries are likely to avoid traps if they encounter them again.

When mounted vertically, TR’s upper jaw provides the lure(s) inside the trap with some shelter from the elements, especially rain, when they’re armed. The upper jaw also denies predators access to lures from the rear of the trap, and TR’s teeth gives them less room to work with on the sides of the trap. The shade that TR’s upper jaw provides, may also reduce the rate at which some lures deteriorate in sunlight.

As I wrote under the Power heading, determining whether or not a TRs springs have weakened is something that I’ve been unable to figure out.

  • Because they’re plastic, there’s only so much abuse that TRs can withstand. Since I began mounting my TRs in tunnels, none of them have been damaged.
  • The only part of TRs that are susceptible to damage, are the edges of the lure cups that screw them into place. I’ve been guilty in the past of using too much force.

I retired 2 traps, recently, because the springs had rusted to the point that I wasn’t confident that they would continue to work properly. These TRs had seen extensive action in tunnels in damp, shady sites, so they rusted far sooner than normal. When I buy my next batch of TRs, I’m going to use a rust-proofing agent to protect them from the weather. I treat my DoC traps with a lanolin-based spray, which has a more natural scent than other protective sprays. I don’t know why it didn’t occur to me before to protect TR springs from the elements, but I’m going to do so from now on.

davidnblake36 uses vegetable oil to protect his TR springs. Rats are fans of oils, so it’s a good way to protect a TR while adding another lure to the mix.

The holes on the rear of TRs, makes mounting them very easy, horizontally or vertically, and they’re strong. Surprisingly, you don’t have to use flat-head screws to mount TRs, so you don’t have to go on a search for a specific type of screw.

You can use nails to mount TRs, but I don’t recommend it. It’s difficult to hammer a nail down far enough that you’re able to set the trap, because parts of the plastic base get in the way, and removing a nailed down TR without breaking it is nearly impossible.

When vertical trapping, one thing that you can try is to mount TRs using only 1 hole, allowing the trap to hang on an angle. In this position, it can be more difficult for predators to access the lure cup without triggering them. I don’t know how effective this technique is, because I don’t trap in trees (yet).

Due to their longevity, TRs are an affordable trap to use on a cost-per-year basis. Brand name T-Rex and Tomcat traps will usually end up costing you about $15 apiece. On average, my traps last for about 3 years, so that’s $5 per year of service.

My 3-year average is skewed low, because unmounted TRs often fly around when they go off, so some of the first traps that I used were smashed to bits. For example, one TR only made 2 kills before it went in the trash, because it struck the concrete floor of a shed several times from the top of workbench, when it had killed a large rat.

Inside tunnels, the average field-life of TRs may be closer to 5 years than 3. They receive more protection from the rain, which significantly delays the rate at which the springs rust. They don’t have to be retired once the springs go rusty, however, because TRs with rusty springs are still capable of making kills. I use a small metal brush, which is similar to a toothbrush to remove the rust, because it may clog up the springs.


A design flaw of the TR is the fact that predators can’t access lures when the trap is disarmed. If there was a safety setting that permitted pre-feeding, it would be a huge improvement. There are several snap-trap models on the market similar to the TR that do have a hole through the lid for pre-feeding, but I haven’t used them, so I don’t know how well they perform.

There is a simple solution to this problem, however. I apply a lure onto the top jaw of the trap and allow predators to eat it off of the plastic. Once the upper jaw has been cleaned several times, I re-lure the trap using the cup. There will be some predators that are put off by the change of the site of the lure, but there’s no way to avoid this neophobic response.

Sensitivity Settings
By gently tapping down the end of the treadle when TRs are armed, its sensitivity will increase, but the difference is minimal. If TRs are being raided by mice and small rats, for example, adjusting the treadle to its most sensitive setting may kill a few small rodents, but the lower treadle height makes it easier for rats and mustelids to lean over the treadle to the cup.

The sensitivity settings of other snap traps, like the Victor Pro and Connovation’s D-Rat Basic and Minimalist, however, can be adjusted to the point that the odds of killing small rodents increases significantly.

The Bait/Lure Cup
Some rats are able to eat lures out of TR cups without triggering the treadle and small rodents can lick cups clean long before rats turn up.


Use Tunnels
It’s easier for predators to eat and steal lures from the sides of TRs, because the distance between the lure cup and the edge of the trap is smaller than at the front, and the treadle is far less sensitive on the sides. The teeth do make it harder for predators to access the sides of TRs than other snap traps, but this does little to reduce the flaw. Inside tunnels, predators can only interact with TRs head-on, which eliminates the flaw.

A head-on strike is more likely to result in a clean kill, because the full force of the springs is released. Trapped on the side, TRs don’t deliver as much force, making the jaws less effective. The odds are much higher that a predator will escape from the sides of TRs outside of a tunnel.

Mount Your Traps
When TRs go off, they are often sent flying by the force of the springs, because they’re so light. After only using them for a few months, I had to throw out 2 of my first 5 TRs, because they’d broken after a number of collisions with solid objects and/or concrete floors in sheds. With the weight of a large rat in its teeth, these traps can strike objects with considerable force.

Inside tunnels, I use screws to mount my TRs to the base, because I’ve had scavengers pull a trap to the front of a tunnel, in an attempt to remove the entire carcass. I haven’t lost any traps, but I’ve had to replace the bent and stretched mesh baffle on several tunnels.

Lure Cup Tips
In every snap trap model that uses bait/lure cups, predators are capable of consuming lures without setting off the trap. I’ve experimented with a number of different lures and techniques, in an attempt to reduce the odds of this occurring, with mixed success.

Tip 1
Use a form of “paste” lure, like peanut butter or Nutella, as the base for a solid lure.

  • The stickier the base lure, the better. You want to use a base lure that keeps the solid lure as secure as possible. Standard lures like PB and Nutella work reasonably well, but there may exist superior edible base lures. Mixing something into a paste lure might increase its stickiness, but I don’t know which substance(s) might work.
  • A base lure doesn’t have to be organic, however. If the solid lure is attractive enough to them, rats might ignore the smell of an artificial adhesive. It’s also possible that the scent of particular adhesives will either appeal to some rats or make them curious.
  • The harder the solid lure, the better. Rats eating a solid lure out of TRs have to use more force with their jaws, increasing the amount of movement within TRs.
  • Experimenting with lures
  • When eating a solid lure, rats may have to change the way that they interact with TRs. Rats that are accustomed to eating paste lures out of TRs, may have to change the way that they eat of the trap when solid lures are used, putting themselves in more dangerous positions.

In the first scenario, predators decide to eat the solid lure on top of the paste base. Nibbling or chewing on solid lures takes more effort than eating paste or “soft” lures, like egg mayo, so predators will generate enough vibrations/movements to spring a TR, sometimes.
Eating solid lures also takes more time. The longer that predators spend at a trap, the more opportunities there are for mistakes to be made.

In the second scenario, predators may have to change the way that they eat out of TRs, potentially placing themselves at greater risk. Predators that normally lean over a TR to lick up lures, may be unable to eat solid lures without making contact with the treadle, for example.

In the third scenario, predators can be killed when they attempt to remove a solid lure from the cup, using their teeth and/or paws. If a paste lure provides enough resistance, the movements created by predators attempting to pull away the solid lure, could be enough to spring the trap.

In the fourth scenario, a predator that has no interest in the solid lure, attempts to get it out of the way, using its teeth, snout or paws.

  • The use of edible solid lures in TRs takes advantage of predators’ desire to cache food, which probably makes them take greater risks than if a standard paste lure is in the cup.
  • Ideally, solid lures that are level with the height of the lure cup or shorter, will leave only a small gap between the edge of the lure and the edge of the cup, so predators will find it more difficult to use their paws.
  • It is important to use solid lures that are relatively short. The taller a lure is, the easier it is for predators to grab it from the sides with their paws.

The best solid lure that I’ve used, so far, are dry chickpeas. They’re as a hard as a rock, so some serious biting is required to eat them. Chickpeas are about half the size of a great solid lure, unfortunately, but I’ve killed enough rodents using them, that it’s become standard practice. They’re cheap and easy to use, so I’d give them a try.

Tip 2
Use a solid lure in the cup that is difficult for predators to eat due its texture. The best lure that I’ve found, so far, is Erayz preserved rabbit. The next item on my list of lures to try, is beef jerky.

  • I cut squares of Erayz that are about 10% larger than the width of the cup. This ensures that it stays tight in the cup. Fill the base of the cup with a paste lure and press the Erayz on top of it. Erayz is really stinky, sticky stuff, so wear gloves!

  • Erayz is marketed as a mustelid lure, but I’ve trapped plenty of ship rats, brown rats, and hedgehogs with it, so it’s a good multi-species lure (not all of those kills were in TRs). I do think that it’s safe to assume that your odds of trapping weasels and stoats in TRs will be higher using Erayz, compared to lures targeting rats.

  • The time to try Erayz in your TRs is spring and summer, when small mustelid activity reaches its peak. Keeping a few TRs lured with Erayz all year, should increase the odds of trapping mustelids during autumn and winter.

  • A bonus to using Erayz, is that it’s a very effective way to kill small rodents in your TRs. Its firm texture makes it difficult for them to eat, so small rodents spend more time in the TR than they would if a paste lure was being used. As a result, I’ve had numerous double-kills and my only triple-kill, using Erayz, because small rodents slowly nibbling away at Erayz are often joined by others, which increases the amount of weight on the treadle.

  • In wet weather, Erayz can go moldy quickly, for a jerky-like lure, because it’s quite good at absorbing water. When I first used it, I couldn’t believe how little time it took for a leathery, brown piece of Erayz to turn into greyish mush. I give Erayz a thin coating of Goodnature’s Meat Lovers’ blood lure, to keep it waterproof, which prevents the growth of mold.

Lure Recommendations

#1 - Goodnature lures
The Meat Lovers’ lure (ML) has been the most effective lure in the Goodnature range that I’ve used, because it has been able to attract every invasive carnivorous and omnivorous species in the areas where I trap.

  • Like the other Goodnature lures, ML is long-lasting, so you don’t have to worry about it going stale or rotting; it’s water-resistant, so it’s a great lure if your snap traps are in damp sites or exposed to rain; it’s mold-resistant, which gives it a huge advantage over conventional edible lures; and I have yet to find any evidence of insects or slugs/snails consuming it (after 4 years).

  • I’ve discovered that I can prevent ants, cockroaches and tree weta eating my lures, by applying a coating of a Goodnature lure onto my lures. Years ago, ants were raiding my TRs, stripping them of lures within 2-3 days. I placed a pair of TRs next to each other inside a tunnel. One cup contained PB and the other cup contained PB coated with ML. When I visited the tunnel a few days later, the ants had eaten about 3/4 of the PB, but they hadn’t touched the ML-coated PB. I’m forced to conclude that Goodnature lures block insects’ sense of smell.

  • Goodnature lure sachets are both user-friendly and inexpensive, with sachets typically costing approx. $12. I only need 2 sachets of ML a year, despite frequent use.

  • Goodnature lures have the disadvantage of being fairly thin, because they weren’t designed to be used in snap traps. As a result, some predators are able to lick it out of the cup easier than most lures. That being said, I have trapped a significant number of rodents using Goodnature lures on their own (the vast majority of them with Meat Lovers’). I recommend using solid lures with Goodnature lures, however, because predator kill rates should be higher.

Note: There is a risk of blackbird and song thrush by-kills using ML in DoC tunnels. I haven’t killed a bird in my TRs, because they’re inside tunnels with smaller entrances. If you should kill a blackbird with a TR, don’t let it go to waste. Dead birds are excellent lures, because scavengers are attracted by the food and the feathers for their nests or dens.

#2 - Tallow (rendered fat)

  • On January 24th, I wrote a post titled Trappers, please try this lure, that describes the use of tallow as a lure.

#3 - White Fats

  • If you can’t buy tallow, you can make a DIY version using the fat from frying or cooking meat.
  • Pour the fat out of the pan or roasting dish, into a glass or ceramic container and allow it to cool down to room temperature. Cover the container and put it in the fridge.
  • After an hour or so, the fats will have finished separating, leaving a top layer of firm, whiteish, saturated fat. Use this layer of fat to fill up your TR cups. A small spoon is the easiest and cleanest way to apply the fat.
  • Ttry spreading fat onto the treadle. Predators can set off TRs if they lick the fat with enough force. This is a good time to tap down the treadle to make it more sensitive.
  • Pork, beef, lamb, and mutton are the best meats to collect saturated fat from.
  • Bacon grease is the easiest lure to make, because all you have to do is wait for it to cool down. Bacon’s strong smell and salt content may also make it more appealing to predators than plain white fat.
  • The liquid fat below the white fat is still very attractive to predators, so I pour it into small tins, which I put inside my DoC tunnels.

Hi, good post.

Do you oil the springs at any time? I know they get pretty rusty. And if so, do you use a vegetable oil that doesn’t smell that much?

I’ve caught big rats with these too. This post has reminded me some of my traps are over 3 years old.

The other thing is I have foul caught quite a few rats with T-Rex’s. By the legs usually - in tunnels.

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Hey, great post, really well done and well documented. To be honest I have never caught anything or even ever had a T-Rex trap go off. I’ve caught some pretty big rats with Snap traps but absolutely no luck with a T-Rex. I have wondered because I use them in tunnels if they are put off by not seeing through the trap and cant see to the other side of the tunnel? Just a thought…

They are good traps, stats suggest very good, possibly because many of them are used outside of boxes (better interaction rates.)

A simple trick to prevent all the lure being taken from the cup is to put the lure (or at least some of it) under the handle, and on the underside of the hood. Far more likely to stand on the treadle…

Also lure under the handle doesn’t attract the birds.

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Thank you for the compliments. I hadn’t actually finished the post, so I was annoyed when it appeared.

I’m really surprised that you didn’t trap anything with the T-Rex. Had you been using it the same way as your other traps? The same tunnel design, the same lures, similar sites?

Because rats have an excellent sense of smell and terrible eyesight, I wouldn’t expect the use of see-through tunnels to make a significant difference to trapping rates, but I don’t know. I’ve read that weasels and stoats prefer see-through tunnels to enclosed ones, which is one of the reasons why DoC double-sets have higher trapping-rates than single-sets.


Great post Willowflat_warrior! Even if it’s not all there yet… :face_with_diagonal_mouth:

I’ve not had much luck with my T-Rex, but a lot comes down to different locations having differing amounts of food available. Eg I live on an avocado orchard, so they have a choice for most of the year. I find ship rats are easy to catch in most traps - especially when mounted up a tree, but I’m having a lot of problems getting Norway Rats to go near any trapping device lately. I end up shooting them instead - thermal spotter + night vision makes it fairly easy if they’re out and about.

What’s been your most effective mounting position out in the bush (away from refrigerators and firewood!)?

What lure do you find is best for Norway rats?

I recently got some footage of a cat licking the mayo from the cup and you say is possible.

Thanks, Cam

I haven’t been oiling the springs, but I’m going to start doing it. With my DoC traps, I use CRC Lanocote, which is made with lanolin from wool. I don’t know a thing about using organic oils.

After 3 years using multiple T-Rex’s, I’ve only trapped rats by the front paw a few times. My tunnels are either custom-made or modified standard designs, which may partly explain why injuries are so infrequent.

I make my tunnels just large enough to hold snap-traps, so that it’s harder for rats to eat or steal lures without placing themselves in danger. If the trap is 10cm tall, I’ll put 1cm of space between it and the lid, for example. Being in cramped conditions, compared to most other tunnels, doesn’t seem to bother the rats where I trap. If it does, there’s a roomy DoC tunnel down the trail for them to explore.

I mount all of my traps to the base of my tunnels, to stabilize them and to prevent them from breaking. It could be that rats are more likely to get injured when they set off unstable traps.

Good trapping!

Yes that makes sense, might give that a go and try a different approach…cheers!

Hey, yea I’m not sure whether or not being able to see through the trap is a deterrent or not ( I have heard that a Rat’s eyesight isn’t great, but am at a loss why these traps have been ineffective-for me, anyway). I have used T-rex in the same boxes with the same bait that I have caught rats in using other traps. As suggested by yourself and another member I might try them outside of boxes and apply the lure slightly different. I have seen plenty of posts where other experienced trappers like you have had good results. I’ll try a different approach haha. To be fair rat activity has been remarkably low this winter, where as mice catches have been very high.

Great information.
I have had very good success with the T-Rex traps.
All are placed in tunnel-boxs with a Times Up mouse trap to help prevent bait theft from the TR.
Incidentally the catch rate of mice to rats and other species for the last 12 months June 22 to June 23 was over 3 times greater at 93 rats, 374 mice and 9 other.
The TR traps killed ship and Norway rats, weasels and small hedgehogs.
The best treatment for rust treatment and rust prevention, has been an aerosol can of Canola Oil Spray (mild flavor). This cooking oil spray also has a restorative effect on the plastic body of the trap.
It definitely doesn’t deter the targeted species, but in fact, I think, adds to the appeal of the bait odour.

Peanut butter seems to work best for me to catch Norway rats.

Seeing as you lots of mice around, it should be noted that they are a very good lure for rats, weasels, and stoats. In DoC tunnels, you can put them underneath an egg, use them instead of an egg in the holder, you can skewer them, and you can place them directly onto the far side of the treadle (using the safety clip, of course). In order to grab the mouse, predators have to stop on the treadle, instead of travelling across it, so the really fast ones are more likely to get killed. It’s one of the best ways to trap predators that are normally too light to set off DoC traps, because making them stop on the treadle, combined with the weight of the mouse, can be enough to set off a trap.

With a T-Rex, you can place a mouse past the hole where the lure cup sits, with its tail facing outwards. It’s easier for a predator to grab the head than the body, and the small tail is an enticing visual lure. It’s difficult for predators to reach over the treadle far enough to get the mouse, without making a false move. Because they’re so small and light, this is one of the best ways to kill female weasels. Only once has a predator been able to steal a mouse out of a T-Rex. The rest of the time, I’ve either had a kill or had to replace it with a fresh one.

Obviously, using mice as lure in a T-Rex is better in cooler weather, because you might get 2-3 days out of it. In summer, a mouse can start to rot pretty quickly, but it’s also a great time to trap stoats. Hungry juveniles will jump at the chance to scavenge a mouse, as will female stoats, which mainly prey on mice when they’re lactating, and mice are always on the menu of female weasels.

If you have a few mouse traps close to home, you might trap enough to keep a few tunnels lured. I keep a mouse trap double-set next to several of my DoC tunnels, so that I can use mice as lures, and to minimize their interference. The red and white mouse traps that Mitre 10 sells are the best traps that I’ve used. My tunnels have 2cm diameter holes in plywood, to reduce the interference of larger predators with the mouse traps and to prevent the traps being stolen by scavengers.


There are so many birds where I trap, that I have to be very careful where I site my traps and which lures I use. Placing traps in open spaces isn’t an option for me, unfortunately. Before I started using tunnels, 5 of my traps were stolen by scavengers in 6 months, so it’s a funding issue, too!

I’ve tried both of the techniques you suggested, but they haven’t worked very well. I’ll try them again, though.

I conducted an experiment earlier in the week, to find out if I could superglue lures to the treadles of T-Rex traps to make it very difficult for predators to pinch them, forcing them to eat them on-site. I chose Werther’s Originals, because they’re hard and brittle, so I figured that a proper bite would create a lot of vibrations.

Well, small rodents were able to remove them from both of the traps. I’d increased the sensitivity of the T-Rex’s treadles, too, but it didn’t make any difference. It’s possible that the glue didn’t set properly, so I’m going to give it another go. The strong smell didn’t put them off, which is good to know.


Try using white fat in the cup. The next time you have a roast or fry-up, put some of the fat in a glass or tin and let it cool down. Spoon the firm, white fat at the top into the lure cups. The fat can come from any kind of animal. If you run a lot of traps, tallow is an easy, cost-effective alternative.


I’ve made some small tunnels for my Times Up mouse traps that I keep next to some of my DoC tunnels or T-Rex tunnels. I wish that it was possible to mount the traps with a screw. I’m going to try superglue with one.

Nice numbers!
I’ve killed way more rats and mustelids since I started trapping small rodents in large numbers. I live on a small rural property where there are a number of buildings surrounded by patches of mature and regenerating bush, scrub, and pastures. With 8 good traps and frequent checking, I’ve been able to knock small rodent numbers way down. I killed 262 in 2022 and I’m up to 190 so far this year. It’s great to find rat and stoat traps that have intact lures, or ones that haven’t been interfered with very much.

I’ll give the oil a go. How frequently do you re-spray the springs?

Before I started using tunnels, 5 of my traps were stolen by scavengers in 6 months, so it’s a funding issue, too!

Maybe try a long soft wire loop (steel fishing trace) through the base of the trap. Put a fencing staple into something immovable (tree, post, etc) and thread the loop through the staple, and over the trap. I’ve not lost any this way :crossed_fingers: Our local school screws them down through the base, this works well, but I had a couple broken off by a cat stealing the catch. I stick to the wire now.

I was pretty new to trapping when the traps went missing, and there were way more predators around to pinch them (nobody had been doing any pest control on the property). In hindsight, I should have been attaching them to surfaces. The traps that aren’t in tunnels are screwed down. Thanks for the tips.

Likewise, thanks for the intel. Enjoying your artisan approach to the business.

Wow, lots of info. Thank you! Yes I have found the small red and white traps are the best mouse traps, I have made small boxes to put them in which has improved the kill rate with a cleaner capture. Will have a crack at using mice as lures as you suggested. Awesome advice and well explained. Cheers!

Artisanal Pest Control at your service!
Does that mean I can charge customers extra?

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