Rats are smart. Like, scary smart. If you've ever tried to clear an infestation from a crawlspace or a barn, you know they don't just wander into traps because you put some peanut butter on a plastic trigger. They have "neophobia"—a literal fear of new things—and they’ll watch their buddies die before they touch a bait station. That is exactly why one bite for rats (formally known as One Bite™ by Farnam) became such a staple in the pest control world.
It’s a heavy-hitter.
Most people think all rat poisons are basically the same, but that’s a dangerous assumption to make when you’re dealing with second-generation anticoagulants. One Bite isn't your grandfather’s bait. It’s formulated with bromadiolone. While "first-gen" poisons like warfarin required the rat to eat the bait multiple times over several days to actually keel over, bromadiolone is designed to do the job in a single feeding. One meal. Done.
But there is a massive catch.
Just because the rat dies from one "sitting" doesn't mean it dies instantly. It actually takes a few days for the internal hemorrhaging to start. This is a deliberate "feature" of the chemical design. If the rat died immediately after eating, the rest of the colony would see the body next to the bait and never touch the stuff again. By delaying the effect, the poison tricks the whole pack into thinking the food is safe. It’s a grim, effective bit of biological warfare.
Understanding the Bromadiolone Factor in One Bite for Rats
Bromadiolone is the engine under the hood here. Chemically, it’s a chronic rodenticide. It works by messing with the rat’s liver, specifically blocking the recycling of Vitamin K. Without Vitamin K, the blood loses its ability to clot. Eventually, the rat just... leaks. Internally. It sounds brutal because it is.
What makes one bite for rats particularly effective in agricultural and industrial settings is the "bait acceptance." Farnam uses a specific blend of grains that rats actually find tasty. If you put out a bait that tastes like chemicals, the rat will ignore it. One Bite is designed to be highly palatable so that the "one bite" actually happens.
Honestly, the name is a bit of a marketing play, though. While the lethal dose ($LD_{50}$) for a rat is technically contained in a very small amount of the bait, most rats will sit there and gorge themselves until they’ve eaten way more than a single "bite." The key is that they don't need to come back the next night.
Why Professionals Use Bar Bait Over Pellets
You’ll notice One Bite usually comes in 1-pound bars or smaller chunks with a hole through the middle. There’s a legal and practical reason for that. If you use loose pellets, rats will often "hoard" them. They’ll pick up a pellet, carry it back to their nest, and drop it. Maybe they eat it later, maybe they don't.
But when you use bars, you can nail them down or wire them into a bait station. This forces the rat to eat the bait right there. It also prevents the rat from dragging a chunk of poison into a pile of dog food or a child's play area.
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If you're using this stuff, you have to be obsessive about placement.
The Secondary Poisoning Risk No One Likes to Talk About
Here is the part where things get complicated. Because one bite for rats is a second-generation anticoagulant, it lingers in the rat’s system. If a Cooper’s Hawk or a neighbor’s barn cat catches a rat that has eaten One Bite but hasn't died yet, that predator is now eating the poison too.
This is called secondary poisoning.
It’s a huge point of contention in the pest control industry. Some states, like California, have moved to heavily restrict these types of second-generation anticoagulants (SGARs) because of the impact on local wildlife populations. Bromadiolone is more persistent in body tissues than older poisons. If you have an owl box on your property, you might want to rethink using One Bite. It’s effective, but it’s a blunt instrument.
You have to weigh the risk. If rats are chewing through the electrical wiring in your combine harvester—which can cause thousands of dollars in damage or a fire—you need a fast solution. But if you’ve just got one stray mouse in the kitchen, this is probably overkill.
Handling and Safety: Don't Be Casual
I've seen people handle bait blocks with their bare hands. Don't do that. Not just because of the poison risk to you, but because rats can smell human scent. If you leave your scent all over the bait, they might avoid it. Use gloves.
Also, Vitamin K1 is the antidote. If a pet gets into One Bite, you need to get to a vet immediately. They will start a weeks-long regimen of Vitamin K1 to keep the blood clotting while the bromadiolone works its way out of the system. It’s an expensive mistake to make.
Where One Bite for Rats Fits in Your Strategy
You shouldn't lead with poison.
Integrated Pest Management (IPM) is the "gold standard" used by pros like the folks at Orkin or Terminix. It means you fix the holes in your walls first. You clean up the spilled grain. You remove the water sources. If you just throw poison at a rat problem without fixing the environment, you’re just creating a vacancy for new rats to move in.
Use One Bite when the population has exploded and you need to knock the numbers down quickly. It’s for the "knockdown" phase.
- Target Areas: Use it in rafters, between walls, or in crawlspaces where pets can't reach.
- Bait Stations: Use tamper-resistant stations. No exceptions. It keeps the bait dry and keeps the "non-targets" (dogs, kids, squirrels) out.
- Monitoring: Check the bait every few days. If it’s gone, replace it. If it hasn’t been touched in a week, move the station. Rats follow specific "runways" along walls; they rarely cross open floors.
One Bite for rats is powerful because it overcomes "bait shyness" better than almost anything else on the market. It’s a tool for a specific job. It isn't a "set it and forget it" solution, and it requires a level of respect for the chemistry involved.
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Essential Steps for Safe Deployment
If you are going to use this product, you need a plan that goes beyond just tossing a bar under a porch. Start by identifying the "active" runs—look for greasy smudge marks along baseboards or walls. That's where the rats' fur rubs against the surface. Place your One Bite stations directly in these paths.
Always secure the blocks. Use the rods inside the bait station to spear the blocks so they can't be carried away. This ensures the "one bite" happens on your terms and within the safety of the box.
Finally, be prepared for the smell. Unlike some myths suggest, there is no poison that "mummifies" a rat or makes them go outside to find water so they don't smell. If a rat dies in your wall after eating One Bite, it will smell for a few weeks. That’s the trade-off for using a high-potency single-feed bait. Use a borescope to find the carcass if the smell gets unbearable, or stick to snap traps in areas where you can't afford a hidden "stink" situation.
Know your local laws before buying. Because of the environmental impact, some jurisdictions have moved bromadiolone to "restricted use" categories, meaning you might need a license to buy it in certain quantities. Always check the EPA registration number on the label to ensure you're using a legal, vetted product for your specific environment. Using agricultural-grade One Bite in a residential kitchen isn't just a bad idea—it’s often a violation of federal law. Ground your pest control strategy in safety first, and let the chemistry do the heavy lifting only when necessary.