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Rat Poisons and Wildlife: What’s the Big Deal?

Nobody likes pests, hence why pesticides were invented. Rodenticides are a specific type of pesticide used to control rats and mice, but they can have impacts throughout the food chain if not used correctly. In this episode, we will explore the science behind rodenticides, the impact of rodenticides, and of course, best management practices when it comes to controlling rodents in our yards and neighborhoods.

 

Episode Transcript:

SHANNON:
On today's episode, we'll be talking all about rodent control. So what do you do if you have a rat problem? Do you use poisons? What about traps? And maybe you can just get an owl box?  Learn more on today's episode.

LARA:
Welcome to “Naturally Florida,” a podcast about Florida's natural areas and the wild things that live here. I'm Lara Milligan.

SHANNON:
And I'm Shannon Carnevale.

LARA:
This podcast is brought to you by UF IFAS Extension in Polk and Pinellas Counties.

SHANNON:
Hey, Lara, I heard through the grapevine that you guys are dealing with a bit of an issue because you've had some really popular owls die in your county. Can you tell us a little more about that?

LARA:
Yeah, it was really sad. It started in one of our parks, and then there was a similar incident in a city park. And so there's just been lots of media coverage about the death of these owls because in particular one of the parks people flock to see its great horned owls. And they come there every year when they're nesting to photograph them.

It's a huge draw for visitors and residents. So when they passed away, obviously media took advantage of that opportunity. And, therefore, I got lots of phone calls about, you know, what happened. Turned out it was due to rodenticides or rodent poison or rat poison. I don't know, Shannon, what do we want to call it? Rat poison?

SHANNON:
Let's go with rat poison for simplicity’s sake. But they are technically called “rodenticides.”

LARA:
Yes. So they did get sent off for a necropsy, which is pretty much the only way that you can determine that. They test for certain chemicals. So it was determined that they died from what we would call secondary exposure or secondary poisoning. And so the calls that I was getting after that was, you know, “Are there bird-friendly rodenticides that I can use so that I can take care of the rats and mice, but not cause harm to things like owls and hawks and other bird species?”


SHANNON:
Yeah, that sounds like a really important topic to cover today, but before we do that, let's just go back and connect a little bit more why rodenticides or rat poisons would have an effect on owls.

LARA:
Yeah, so it's definitely like “Wait! What?!”  It doesn't really make sense when you first hear it. And I will say there's many different rodenticides out there on the market. Shannon and I aren't going to go through all of them, but some of the more common ones that are used are what we call “anticoagulants,” which is just a fancy way of saying blood thinners.

So these anticoagulants, basically, they interfere with activation of vitamin K—maybe you're familiar with that in our bodies. But it's basically the key component in blood clotting. And so basically the rodents that we’re trying to kill—the rats and the mice— typically bleed from internal bleeding, which in itself is like a horrific thing to think about.

SHANNON:
Yeah.

LARA:
So that alone might make you like, reconsider ever using rodenticides.

SHANNON:
It's a pretty terrible sounding death.

LARA:
Yes. So the issue is the chemicals within these rodenticides can remain in the tissues of these rodents. And there are two types of anticoagulants, which we'll talk about in a second. But because those chemicals can stay in the tissues of these animals—and often it takes sometimes multiple days for the rodents to die—if those rats or mice are consumed by something like an owl, they can then become exposed to these same chemicals and have the same effect. Basically, they would die from internal bleeding.

SHANNON:
And that makes sense when you think about what type of prey a predator is going to go after. They go after the sick-looking ones or the ones that aren't moving as quick. And so that really does make a lot of sense, unfortunately.

LARA:
Exactly. Yeah. And that's another issue. I mean, not only, it's actually not really well studied in birds, what we would call “sub-lethal exposure.” Kind of what you were talking about—like they've consumed these, they’re kind of like they're sick, they're not dead. They might not ever die, but they're slow to respond. They're just slower in general. So yeah, if you're a predator, you'll be like, “Well, yeah, I'm going to go for that!” 

SHANNON:
Dinner!

LARA:
Yes, exactly. So that's also definitely another thing to think about and consider.

SHANNON:
And you mentioned that we had two different types of rat poison, so just real quick to go over those. First-generation anticoagulant rat poisons were just that—they were the first ones we had access to. The target rodent needed to visit the poison bait multiple times, ingest multiple doses before they accumulated enough of it to have a lethal dose or have enough of the poison to kill them.

Unfortunately, in addition to it being slower acting, we also started to see some resistance building up in the population, which just means that the rat poison wasn't as effective as it used to be and it required more and more of it to have a lethal dose if it even got there. So in an effort to combat the resistance that was being seen in first- generation anticoagulant rat poisons, they came out with second-generation anticoagulant rat poison. And with these new ones, it took only one dose of the poison for the rat to ingest enough to have a lethal effect or enough to kill them.

And so that's first- versus second-generation anticoagulant rat poisons. But, Lara, are we able to use any type of rat poison that isn't an anticoagulant?

LARA:
Yes. So there are non-anticoagulant rodenticides. There's several options out there on the market. But again, same end goal is to kill the rat or mice that you're targeting. So I do just want to also mention, though, for you as a homeowner, you would only be able to get access to the first-generation anticoagulants and these non-anticoagulant rodenticides.

The second-generation are only available at the commercial level. So just to keep that in mind, if you're doing research or anything, you're like, “Why can't I find this particular one?” And that would be why.

SHANNON:
That makes a lot of sense that we would keep the stronger rodenticide in the hands of professionals. Unfortunately, we do know through research that second-generation anticoagulants are still very much associated with that secondary exposure that you mentioned, which can cause death in non-target animals like owls and other birds of prey or other ground predators. So let's transition to some of our non-rat poison options because I think that's really what we want to talk about today.


And if anyone listening is really interested in the rat poison information, we’ll include a lot of that in our show notes. The active ingredients that we're talking about have so many letters in them, we are not going to try and say them on this podcast. I won't be able to pronounce it correctly. You won't remember it  (LAUGHTER) and no one will know how to spell it.

So, Lara, let's move on to something that is  “How can we deal with rats without poison?”

LARA:
Yes. So what we recommend is something called integrated pest management, which is a fancy way of saying use the least toxic method of controlling your pest species first. Do everything you can before resorting to chemicals and poisons. So in the case of rats, one of the first things that we do is what we call “rodent proofing," which is just figuring out if you have them in your building or your home—figure out how they are getting in there and then blocking those entryways.

And that's obviously very oversimplified. (LAUGHTER) Shannon and I can also link to some resources in the show notes for specific ways on how to do that. Or of course, you can always pay a company to do that for you.

SHANNON:
Right. And along the same lines, it's kind of included in rodent-proofing, but it's also a slightly separate thing, which is just reducing the attraction to wherever they're getting into. So you want to keep your home, your garage, your shed—wherever you're having a rodent problem—you want to keep it clean, remove any unnecessary food, water, any tight spots that they could use for nesting, any material they could use for nesting.

Because finding rats’ nests are a literal thing that I do not enjoy. (LAUGHTER) But it's happened. They show up in my shed sometimes. So just keep it all clean and that will help also.

LARA:
Yes. And that's something Shannon and I mentioned, again, in several previous episodes—keeping clean, keeping pet food and other access to food is always beneficial for avoiding pests. 

Another thing you can consider is this idea of supporting the natural predators of things like rats and mice. Now that being said, there's no research that shows if you attract, you know, snakes or owls to your yard, that you will not have issues with rats and mice.
But we know that certain species like rat snakes will consume rats. We know owls—in particular one of the most studied, barn owls—consume a crazy amount of rodents.

SHANNON:
So many.

LARA:
So many. There was one study that looked at a nesting pair of barn owls that consumed over 3000 rodents in just one year.

SHANNON:
It’s amazing.

LARA:
Yes, but we also know rats, like, breed very prolifically. So, again, just keep that in mind. But there are other things, you know, supporting predators in the whole food chain in your yard will just create a nice balanced system. And Shannon and I always like to talk about the ecosystem. And you have your own ecosystem right in your yard.

SHANNON:
Absolutely. And if you think back to our cavity nesting species podcast episode, we gave you all kinds of information about how you could support those cavity nesters. And we have a lot of birds of prey that are cavity nesters, including the barn owl, the barred owl, the eastern screech owl, several other birds of prey species. And so if you need to, go back and listen to that episode or reference the show notes. And you can put up artificial habitat, also known as nest boxes or birdhouses, to support those predators in our urban areas because they are very prevalent in our urban and suburban areas.

LARA:
Yes, yes. Very good point. We always like to point you guys back to some of our previous episodes in case you missed them. Another thing that you've probably heard about or are familiar with as it relates to controlling rats and mice is just using the old school trap, right? Mouse trap.  Wasn’t it even a board game or something?  

SHANNON:
It was an amazing board game.

(LAUGHTER)

SHANNON:
Can I just say I had it and I loved it and I played it all the time and drove my parents insane. Hashtag 90s.

LARA:
Oh, I might need to go find that. (LAUGHTER) So the thing to think about with traps: they are incredibly effective. They're also cheap. But, as with anything, it does take some homework before. It's not just a “one size fits all”—go to, you know, your home goods store and buy a trap and set it out. There's some things you need to consider with that.

The very first thing is identifying exactly what species you have or are having issues with in your home.

SHANNON:
And this is something that maybe we should have mentioned earlier, because it is important for literally any type of control effort that you do. Just like we recommend with plants, you want to know what you're working with before you try to trap it. There are in some parts of the state some endangered or protected mice species. So it's important not to kill those.

But for most of the state and most of the rodent problems that you're going to have in urban areas, they are non-native rodents. And so I think what Lara is getting to—and please correct me if I'm wrong—is making sure that you have the right trap based on the size of the critter you're trying to deal with, especially if it's a non-native rodent.

LARA:
Correct. Yes. So if you’re trying, if you have an issue with mice and you're using a trap for rats, not going to work out so well and vice versa. And Extension's here to help you with identification. Or, of course, you know, your local extermination company can also assist with helping identify what species you have. 

You also need to know what to put on said trap. So it's not the old school… Peanut butter is not —believe it or not—not what we recommend. So there's some homework you can do, again, once you know what species you have. And there's this whole idea of like pre-baiting, which is basically you set out your trap with it not set with your bait on it just to kind of get them used to, like, “What is this new thing? Oh, it gives me yummy food.” And then you set it later.

(LAUGHTER)

SHANNON:
Because they're smart, right? Like they are very, very smart. And so if that trap goes off and it didn't get them, they're going to learn not to come back no matter how good the treat is, right?

LARA:
That's right. Exactly. So and then it's not it's not like you just buy one trap. I mentioned they're prolific breeders. If you have a rat issue, you need more than one trap, and you want to make sure you set them in the right place. Basically, if you know where they're going— you know their travel route—you want to set it there and set a lot of them there.

SHANNON:
Yeah. And something else to consider if you're going to be going the trapping route is… if you're using a lethal trap or a kill trap that everybody should be checking those at least once a day to make sure that the animal is not suffering unnecessarily. 

And if you're using a humane trap or a live trap—they go by a lot of different names,
but essentially it's a trap that doesn't kill the animal when it gets trapped—you have to check those every day and make sure that you're releasing any non-target animal. So if you set the live trap out for a rat, but you catch a vole or some other type of wildlife, that you release that wildlife. 

But if you're checking what species you're trying to trap and you're buying the appropriate trap, hopefully you'll minimize that as an issue to begin with.

LARA:
Yes. And I do just briefly want to mention, because we didn't say this before, with the, going back to the anticoagulants, the first-generation ones that homeowners can get as well as the non-anticoagulants, those can also harm non-target wildlife just right away—like they can come in and eat the bait and be harmed in that way. So, like we alluded to the second-generation being really bad for this, like, secondary exposure, but it's not to say these first-generation and non-anticoagulants are like good rodenticides. They can still cause harm to non-target wildlife, including your pets. So we just want to make sure we made that point very clear.

SHANNON:
Yes. So just make sure if you're using any of those that you're putting them in an area inside a trap that excludes wildlife or putting it in an area where your pet can't access and hopefully other wildlife, too.

LARA:
Yeah. And then I guess the last point of the integrated pest management is, of course, resorting to using rat poison or poison baits. And, again, Shannon and I are not going to go into all the different active ingredients, but I do encourage you guys to check out our show notes and just get familiar with reading the label on your rodenticides.

There's lots of information on there. See what active ingredients are listed, see what the target species are, and what species specifically it cannot be used for. So there's just lots of information on there, including how to apply it and utilize the rodenticide correctly. So I cannot stress that any more. If you're going to resort to it, do it right.

SHANNON:
And there's one type of rat control that we've not talked about, Lara. I just want to throw a plug in real quick. If this all seems a bit overwhelming, we can always consider that calling a local pest control company might be your best option. And you can always ask them specifically if they are going to use poison baits because they would likely be using the second-generation ones.

And you can express you'd prefer they don't use poison baits when they're working on your property. They are there to work for you. So always call around and ask and see if they're okay with that. But hiring someone sometimes, honestly, is the simplest and easiest answer. They are trained. They are experts in this. They know what behavior to look for in whatever the target species is.

And then you can focus your efforts on artificial habitat or keeping the area clean and mess free.

LARA:
Yes. Yeah. And I think that's honestly a great way to end this episode. Definitely if you guys know family or friends that are dealing with rodent issues, share this episode with them. If you do resort to using rodenticides, you know, do your homework. But we really encourage integrated pest management. Or, like Shannon said, you know, just call a professional if you're like, “Y'all are hilarious. I'm not doing any of that.”  (LAUGHTER) 
Just call a professional.

SHANNON:
All right, cool. Well, everyone, check our show notes for all those resources we mentioned. And we hope everyone has a great day. 

Thanks for listening to “Naturally Florida,” a podcast about Florida's natural areas and the wild things that live here. Stay updated on new episodes by subscribing on your favorite podcast platform. If you enjoyed today's episode, consider sharing it with a friend.

“Naturally Florida” is produced by your hosts Shannon Carnevale

LARA:
and Lara Milligan.

SHANNON:
If you have questions or suggestions, submit them online at naturallyfloridapocast.com. This podcast is brought to you by the University of Florida's Institute of Food and Agricultural Sciences Extension, an equal opportunity institution. Thank you for listening.

SHANNON:
The end.

LARA:
I don't know. Yeah. I was kind of thinking I don't know if we want to, like, end on a more positive note.

SHANNON:
Is there? I mean, the topic is roden.. There isn't a positive note. It's rats.

(LAUGHTER)

SHANNON:
Umm..

LARA:
Do what you can to protect our species.

And anyway…Okay.

SHANNON:
Yeah. Yeah. I mean, the only way I can really think about it is if we'd have to redo the whole thing.

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