Saw a rat in a bin aeration fan. How to eliminate them?

Went to turn on an aeration fan yesterday and looking out at me was a rat. There are no constant feed sources on this farm as there is no livestock and I keep grain cleaned up fairly well. There are a couple cats around the farmstead as well. I believe the rat(s) can slip through the grill on the fan and of course live under the air floor. Foundation is good on the bin. They probably are living off of the fines that fall through the perforated floor plus what they might carry in. Next summer my plans are to take the floor up and clean under it. The fan is a good foot off of the ground, but I am positive that is where they enter. I thought I could put a plastic tub filled with used engine oil under the front edge of the fan and drowned them as they come out. So my question is are rats nocturnal? Are they roaming at night and in their shelter during the day? Just trying to catch them in the tub when they come out. Also, I do not want to drive them to another building. I would be willing to take the tub away and move it back during a 24 hour period so I could catch them all if some weren't in the bin at the time I placed the tub. I will certainly set some bait stations as well. Eventually I will put some screen on the fan grill. Any ideas appreciated.

I use Tom Cat cubes. Place them where rats like to live and forage. When one disappears, replace it and continue doing that. One day they will quit disappearing! It may take a couple of years but it worked for me.

Keep in mind that it is not called BAIT for nothing. It ATTRACTS the critters.

It does not seem logical to ATTRACT the critters to where the food is, because when the poison runs out they go right after the food, and frequently bypass the poison for the better smelling and tasting food.

I prefer to set up a perimeter AWAY from the food and places they nest to keep them from even discovering their new home. Bait goes around the edge of the building just inside the walls, not right on top of the corn pile or in the vehicles/tractors/equipment like people usually do. They eat the poison and die before even finding out that The Promised Land lies just beyond.

Rats are nocturnal. They are also intelligent, they are very good at getting to food and shelter!

Exclusion is the best deterrent. If you can, seal up any openings, they find their way in by sensing air currents and smell. Using Pest Block expanding foam helps, block the air and they don't recognize it as a way in.

Cover the air vents with expanded metal or hardware cloth. Mice can get through 1/2 inch hardware cloth, but rats will chew through screen wire.

Also keeping the perimeter clear of grass and stored items exposes them in their effort to get in. They don't like exposure. A gravel or concrete apron works well.

Poison and bait are a loosing battle. You'll never get them all. Best to send them looking for greener pastures on down the road!

(quoted from post at 05:42:35 11/02/21) I use Tom Cat cubes. Place them where rats like to live and forage. When one disappears, replace it and continue doing that. One day they will quit disappearing! It may take a couple of years but it worked for me.

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I use the "Havoc" brand. I put several chunks on a wire and tie it to something. Always keep 3 or 4 chunks on that wire and replace each chunk as needed. Never let all of it be gone. No more issues with rodent damage in my shop, garage, or open front machine shed.

We use Tom Cat also, but recently something chewed the lid off the bucket and started carrying it away, I caught a red squirrel in the act. I bought a big rat trap and baited it with peanut butter and honey, hopefully next time we're at the farm there will be something in the trap.

If they are under the floor, sealing most or all of the entrances during the day and hooking some car exhaust up to it might exterminate a lot of them.

Good luck.

I use the poison cubes, have to put them where the cats or dogs cannot get to them. The key for me has been to leave a half full 5 gallon bucket of water nearby, apparently the bait makes them thirsty and they will drown trying to get to the water in the pail, fall in and cant get out. I have had up to 4 in the pail at one time.

Since a small colony of feral cats set up house across the road I virtually never see a rodent here. Since you store grain in that bin it will be a constant attraction to rodents. Cats are all day all year presences versus other predators of rodents. If it were me I would see if some cats can be acquired perhaps from a local shelter. Treat them humanely including having a place that they can get in out of the weather. I keep all driveways open during the winter in part to know the cats can move to where they think that they should be.

For the bucket idea, fill a 5 gal. bucket up with grain to maybe 4 or 5 inches down from top. Just let them have a feast and a ball for a few days. Keep bucket filled to that level. Then take bucket away, empty, and fill up with water, with maybe an inch or two of grain floating on top of water. Do this so its at the same level in bucket as before (4 or 5 inches down from top). Then the rats will sink through the floating grain and drowned. Pick out the dead ones everyday untill you don't catch any more. You might have to repeat the entire process and start over with a full bucket of grain again, depending on how many there is, and how clever some of them are. Note, you'll have to use grain that will float. If whats in the bin won't float then use another kind that will. Use the same kind through entire process.
The oil thing, there is nothing to bait them to the bucket. It would just be an accident for them to take an oil bath.
The poison thing. Use the nail down. If they can move it, they will. They'll move it back to thier nest, and use it for nest building material and won't eat it. Not enough to kill them. If its nailed down, they'll eat more of it because they can't move it. Then they'll usually eat enough to kill them. With the nail down bait, buy small supplies of it, and change kinds everytime you run out. Don't know how, but using the same kind all the time seems to loose its effectiveness. Perhaps they'll just eat more of something thats new to them.

Go on YouTube. Search 'Mouse Trap Monday. This guy makes a living reviewing traps. Has more rats on his place than anyone I know. How does that work?

I had some outside around my tractors and they kept disappearing. I too had a few squirrels and they may have been the culprits but I also have Raccoons visit my pond every night and its within 100' of the shop/lean to where I kept a couple of tractors.....possibly my invaders.

So I built a box with a long entrance so that their grubbly little hands couldn't reach the bait but the rats could come in and make a (temporary) nest while dining. I like the holes in the middle so that you can string them on a piece of wire and keep the varmits from running off with them.

Others have covered how to control a rat population so I won't go there.
Now the rat under your floor is dead now or will be before long. If the bin is tight as you say. The rat is going to attempt to jump through the axial fan because he can see through the fan but does not know it turning. Splat.
40 years with bins. Mark