Straight Dope Message Board

Straight Dope Message Board (
-   General Questions (
-   -   Effective rat deterrents? (

TSBG 05-15-2016 07:44 PM

Effective rat deterrents?
I live in Southern California, and tree rats/roof rats are a fact of life. I've always managed to deal with the little outbreaks--sometimes bigger outbreaks--with snap traps.

However, something's going on in the crawl space under the roof. I'm not sure that it's rats, because they're active in the day and that doesn't fit the usual rat MO. But I also can't set traps for them--the noise is coming from the least accessible part of the crawl space. Setting traps and checking them would be virtually impossible. If there are rats, I can keep setting traps near the crawl space entrance and hope to lure them closer, but it hasn't worked thus far.

I'm told that rats can be deterred/driven away by intermittent flashing lights. Anyone know the straight dope on these? The sites that discuss them appear to be either trying to sell me a product, or filled with "some people say that..." weasel words.

HoneyBadgerDC 05-15-2016 08:16 PM

Our red squirrel population has grown a lot in recent years, any chance it might be squirrels. I live in So Cal also and have been fighting a rat outbreak. I have caught at least 2 dozen since the first of the year. Mine seem to stay in wood piles and brush mostly.

TSBG 05-15-2016 08:36 PM

It could be squirrels. As I said the behavior seems a little unlike rats, though I also did just get a rat in the access hatch trap. Could be I have both up there.

watchwolf49 05-16-2016 07:17 AM

Muy gato !!!

elbows 05-16-2016 07:45 AM

Poison with desiccant! They eat it, they get really thirsty. They leave your attic in search of water and expire out of doors! (Should they expire indoors the desiccant insures they don't become putrid and rot. They just turn to dust!)

Dag Otto 05-16-2016 10:52 AM

I don't know about flashing lights, but last year I had a problem with rats under my car hood. Two cars actually. I've placed a work light with an LED bulb under the hood when it's parked in my driveway and they haven't returned. So the flashing lights may work, unless the rats can get under insulation or something where they won't see the light.

TSBG 05-16-2016 12:07 PM

Even if I had a cat, I don't think it'd get into the attic without a lot of help, which I decline to provide.

markn+ 05-16-2016 03:44 PM


Originally Posted by TSBG (Post 19333069)
However, something's going on in the crawl space under the roof. I'm not sure that it's rats, because they're active in the day and that doesn't fit the usual rat MO.

I would reconsider this. I've owned pet rats for over 10 years so I'm pretty familiar with their behavior, and you are correct that "active in the day" doesn't really fit rats. They are mostly nocturnal and while they'll sometimes move around a little during the day, to move to a more comfortable sleeping location or something like that, if you're hearing a lot of daytime activity, I'd guess it's not rats. My guess would be squirrels.

But in any case it seems like one of the first actions should be to close up whatever holes or gaps they're using to get into the house. Broken soffit vents are a likely candidate.


TSBG 05-16-2016 04:09 PM

Closing up all holes is a bigger job than I can undertake on my own, partly due to the aforementioned difficulty of moving around in the crawl space, and I don't want to spend the money to hire someone. That's why I was interested in a method of scaring them away; but if they're not rats maybe I need to reconsider everything.

markn+ 05-16-2016 04:47 PM

Do you hear noises at night too? If you hear noise only during the day and not at night, I would say it's almost certainly not rats.


dropzone 05-16-2016 06:26 PM

Well, my solution to everything vermin related is nasty little rat dogs.

TSBG 05-16-2016 06:28 PM

Well, there definitely ARE rats up there, at least sometimes. I just got one yesterday. I'm starting to think though that there is also...something else.

Greg Charles 05-16-2016 06:37 PM


Originally Posted by watchwolf49 (Post 19333882)
Muy gato !!!

Very cat? ;)

Trim trees or other vegetation that might be providing rooftop access. I assume that would help with either rats or squirrels. I've never had squirrels in my attic ... well, except metaphorically.

purplehearingaid 05-16-2016 07:40 PM

I have heard of people putting a fake snake on the roof to keep rodent out , I am not sure if it works. I would the rats would get wise when the snake never move.

markn+ 05-16-2016 11:38 PM

Rats have very poor eyesight. Their main senses are hearing and smell. A rat would probably not even notice a fake snake.


Dag Otto 05-17-2016 07:44 AM

There you go TSBG, you'll need real snakes. Use several of them.

TSBG 05-17-2016 11:34 AM

No way. Then I'd have to get those gosh-darn snakes out of my gosh-darn attic.

that_darn_cat 05-17-2016 01:45 PM

But that's the beauty of it, in the winter the gorillas will freeze to death!

Fridgemagnet 05-17-2016 02:12 PM

I once had something squatting in my attic, as evidenced by the scratching noises coming from the ceiling. I installed some humane catch-and-release mouse traps, but nothing took the peanut butter bait. Then one day I was up in the attic and I got buzzed by a blackbird. Further investigation revealed it had gained entry through a rotten soffit vent and nested in the eaves. I had a summer of being woken up early every morning by hungry chick noises (the nest was right above my bedroom window), but by the autumn the fledglings and parents moved out and I was able to repair the vents.

tl;dr: might be birds.

Bookkeeper 05-20-2016 01:12 PM


Originally Posted by TSBG (Post 19334523)
Even if I had a cat, I don't think it'd get into the attic without a lot of help, which I decline to provide.

I had noises in the attic once, and got out the stepladder to open the ceiling trap. As I was looking around with my flashlight, one of our cats climbed up the ladder, jumped to my shoulder and then into the attic. She came back a few minutes later with a dead mouse, looking very pleased. After that, any time I got the stepladder out for any reason she would hover around until she could climb up and check for mice.

I did find the tiny gap where they were getting in when I saw one climb the outside wall and squeeze in where some mortar had crumbled just where the soffit met the bricks. The cat managed to climb up the extension ladder onto the roof while I was fixing the mortar, but didn't find any mice, so demanded to be carried back down and ignored the extension ladder from then on.

araminty 05-20-2016 05:26 PM

Sorry, OP, it's no fun to be woken up by furry neighbours of any variety. I'd like to advise you, (and others reading the thread), no matter how frustrated you might get, to avoid using rodenticides. They have a knock-on effect on your local wildlife, especially predators like owls.

TSBG 05-20-2016 05:54 PM

Thanks, I'm not into poisons for a lot of reasons including the one you mention. Thank you all for all the replies.

MacLir 05-23-2016 09:40 AM


Originally Posted by markn+ (Post 19336011)
Rats have very poor eyesight. Their main senses are hearing and smell.

Along those lines, I have heard that mothballs act as a repellant.

No practical experience, just hearsay. :dubious:

All times are GMT -5. The time now is 03:06 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.

Send questions for Cecil Adams to:

Send comments about this website to:

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to:

Copyright 2018 STM Reader, LLC.