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Cuban Tree frogs, they’re more than just a nuisance!

Cuban treefrogs are an invasive species in Florida. In this episode, you'll learn how to identify a Cuban treefrogs and how to humanely euthanize them. By choosing to remove Cuban treefrogs from your yard or neighborhood, you're helping protect local native treefrogs, like the green treefrog and the squirrel treefrog.

Episode Transcript:

Hey, everyone, quick disclaimer. Sometimes wildlife management involves the removal or humane euthanization of some individuals for the greater good of the ecosystem.

This episode contains respectful discussion of euthanization.

(FROGS CALLING )

LARA:
Oh my gosh, Shannon, that introduction with the sound of a Cuban treefrog brings me back to my house down in South Florida where I grew up. And I heard that all the time.

SHANNON:
And it's so loud.

LARA:
It's so loud. And it was always, I remember like as a kid, I was like, “Oh, where's that sound coming from? What is that?” (LAUGHTER) And I'd go to my parents' sliding glass door, and it would always be like, right where kind of the two doors meet in the middle, like hanging out right in the little nook there. But, you know, at that time, I had no idea it was a Cuban treefrog.

SHANNON:
Cuban treefrogs are frogs that I feel like most people in the state of Florida, if you're down in the peninsula anyway, people are really familiar with them, whether they know it or not.

LARA:
So what are some ways people can know for sure that they are seeing or have seen a Cuban treefrog?

SHANNON:
I feel like the easiest one for people to learn is simply how big they can get. So while we were preparing for this episode, we reached out to a friend and colleague, Dr. Steve Johnson. Dr. Johnson is an invasive wildlife specialist, and he has been studying Cuban treefrogs for years. Let's take a listen to how he described the size of the Cuban treefrog.

DR. JOHNSON:
They are the largest treefrog that we have in Florida. An adult female could be three to six inches, or six inches snout-vent length, so that's the nose to the rump.

LARA:
So aside from their size, what are some other things that our listeners can look for to identify a frog as a Cuban treefrog?

SHANNON:
Let's pretend we're just talking about adults. So the really big ones, they can vary in color from green, solid green, to green with a pattern. They can be tan, gray, dark brown. I feel like the ones that people send me pictures of, though, are usually a beigey color, almost like concrete. They kind of blend into the house.

LARA:
Yeah, that's often a dead giveaway for me because not many of our native treefrogs have that coloration.

SHANNON:
And they also have this bumpy skin on their back. And, you know, just like all treefrogs, they've got their enlarged toe pads and big eyes. But with the Cuban treefrogs they've got really, really big eyes and really, really big toe pads. If you're not familiar with our native species, you might not be able to use that as a great identifying feature.

But it's like, if you notice they're really big and you notice they got the bumpy skin and they've got the bug eyes, you probably have a Cuban treefrog. I think you've told me before that you are more comfortable identifying small Cuban treefrogs than I am. So could you talk a little bit about what a younger Cuban treefrog might look like.

LARA:
When they're juveniles and they have a more consistent appearance than when they're adults, so they tend to be kind of this darker olive green color, like solid. And then they have reddish eyes, which is kind of a key characteristic when they're juveniles. And then they'll also have a lighter kind of like this pale, almost yellow line that runs along their side.

And that's pretty distinct and common for how all the juvenile Cuban treefrogs look.The red eyes is really what you'd want to kind of hone in on.

SHANNON:
I'm more comfortable with the identifying features of juveniles when you actually have them in your hand, which many of our listeners probably aren't going to want to do. (LAUGHTER) But if you actually have a Cuban treefrog in your hand and you hold it up to the light, its thighbone is bright blue. And so that makes it really easy for me.

The other thing that the Cuban treefrogs have, once they get to be about an inch and a half in size, is the skin on the top of their head is fused to the skull. So, yeah, so if you take your hand and you put it up on your scalp and you wiggle it back and forth, you'll feel the skin on your skull move around. With a Cuban treefrog if you do that, as long as they're already an inch and a half long, the skin won't move. It's completely attached to their skull there. So that's another way that you can tell them apart, but you have to hold them for that part.

LARA:
We've been talking a lot about, you know, just saying treefrogs and, you know, if you see it climbing on the wall it’s a treefrog. So for our listeners, maybe we want to take a quick step back and just talk about what makes a treefrog, a treefrog versus a toad, and just kind of break down those categories a little bit.

SHANNON:
That's a great idea. Frog species in general, when we're looking at biology and trying to categorize them, like a lot of our other critters we categorize them based on the habitat you're going to find them in. So that means that treefrogs are normally found in the trees or in urban areas on houses or other structure. And to do that, they have those large toe pads we talked about.

We also have aquatic frogs that are found almost all the time in or near water. And then we have frogs that we call terrestrial frogs, which are just frogs that are found on the ground. This is also where you find toads. So toads are just a type of frog. Like chocolate, all dark chocolate is chocolate, but not all chocolate is dark chocolate.

LARA:
(LAUGHS) A great example!

SHANNON:
So, all toads are frogs, but not all frogs are toads.

LARA:
Perfect. Thank you. Yeah, I think that's helpful for people. And I know for you and I, whenever people, you know, send us in images for identification, you know, that's an easy way for us. You know, if it's up on a fence or up on a wall, it's a, you know, it eliminates the possibility of it being a toad.

SHANNON:
Yeah. Which is important when we're talking about areas that also have cane toads or bufo toads, which aren't the subject of today's podcast but they're a hot topic. And when we get emails of people who are concerned they have a cane toad, if it's on a wall, it's not a cane toad. But if it's that size, it's probably a Cuban treefrog.

LARA:
Right. And kind of another thing, we've been saying this term and talking about Cuban treefrogs throughout this episode. And I think it's easy to think “Hmm well, it's called a Cuban treefrog so maybe it's from Cuba.” But let's maybe share a little bit with our listeners about where these Cuban treefrogs came from.

SHANNON:
So they are actually native to Cuba. They're yeah. They're also found in some parts of the Bahamas, and they're thought to also be native to some of the other islands in that general region. But they were first observed in the 1920s in Key West. We think they came in through the Port of Key West, either on passenger boats or on cargo that was being shipped on those boats.

LARA:
Unfortunately, once a lot of our invasive species enter into Florida, or I guess they're not quite invasive when they first enter, but they are able to really take advantage of the environment here in Florida. And Cuban treefrogs are no exemption of this, and they have spread all throughout South Florida, all of Central Florida. They've worked their way into North Florida, but haven't really established healthy populations into the like the Panhandle area of the state. There are sightings from time to time and there's ongoing research and efforts, and that includes you guys to help document sightings of these invasive treefrogs throughout the state.

SHANNON:
Absolutely. And while I was talking to Dr. Johnson, I asked him if he was still looking for citizen reports of new Cuban treefrog populations around the state. And this is what he said:

DR. JOHNSON:
I'm still wanting. I don't need reports anymore from the peninsula, but I'm still looking for reports from individuals or any of our county agents who happen to talk to an individual of Cuban treefrogs from locations in the Panhandle.

SHANNON:
So if you're in the Panhandle of Florida and you see a Cuban treefrog or what you think is a Cuban treefrog, we will put in our show notes today how you can report that sighting and help our research related to the Cuban treefrog advance even further.

LARA:
We love to get you guys involved in helping out in any way you can. And this is a great way you guys can contribute to science and hopefully ultimately help protect some of our native species.

SHANNON:
You mentioned that they were invasive. Cuban treefrogs are also found in small parts of southern Louisiana and in southern Georgia. Currently, we're expecting that you're going to start finding more population throughout the Southeast. So even if you're outside of Florida, consider calling your local extension office and reporting any Cuban treefrogs you're finding in your area. Because, as Lara mentioned, these are invasive species in the state of Florida.

They're invasive in the truest sense of the word. They create negative impact on our ecosystems. But they also affect people's quality of life and cause some economic harm as well. So, Lara, do you want to talk a little bit about our ecological impacts they have?

LARA:
Darn, I thought you were going to go on quality of life because I was ready to chime in there because (LAUGHTER) one of my friends recently texted me a picture of a Cuban treefrog in her toilet.

SHANNON:
Oh, my gosh. Yeah. Go with quality of life.

LARA:
Obviously, nobody wants to, you know, wake up in the morning and find a Cuban treefrog in their toilet. So that's one aspect of quality of life I guess, thinking about, “Okay, well, how did it get in my toilet?” So they can also cause a series of plumbing issues as well as even electrical issues, depending on where they, I guess, navigate in your home.

Having a frog in your house probably for most people is not something they'd say would add to their quality of life.

SHANNON:
You mentioned it earlier in the episode, also how loud they can get. So if you have a large breeding population outside of your bedroom window, I don't even think earplugs will drowned it out properly.

LARA:
Yeah, that is definitely something I get either complaints of, people like don't even know what it is and they’ll record the audio and email it to me and be “I can't sleep! What is this noise?” And it's either that or a limpkin, but that's another story for another day.

(LAUGHTER)

SHANNON:
For sure. And there's another thing that they can do, especially if you have young kids who like to catch frogs and catch other things that are outside. They have a mucous secretion on their skin. And that mucus, if it gets on your skin, can cause an allergy-like reaction with your mucous membranes. So let's say your ten-year old little boy outside catches his frog and he's so excited and then he lets it go, but he doesn't wash his hands.

And then he rubs his eye later. You would have no idea why his eyes are red and inflamed and possibly swollen. And it's entirely possible it's from the Cuban treefrog. So any time you're handling these animals, if you handle them, make sure you wash your hands really well afterwards.

LARA:
And then kind of transitioning to the impact on our ecosystems. I have actually been a witness of a Cuban treefrog eating one of our native treefrogs, and it was not an exciting thing to witness.

SHANNON:
Yeah. And I think that's a great reason to care about the fact that we have these Cuban treefrogs. So it's one thing to say, “Oh, but they're just another species of frog. They're spreading naturally through our state. Why aren't they a good thing?” And it's a lack of biodiversity that can happen after an invasive species comes in.

And it's more than just eating our native treefrog species. As Dr. Johnson explains, they also have an advantage when it comes to reproduction.

DR. JOHNSON:
Capture-mark-recapture studies showed Cuban treefrogs grew and matured substantially faster than two species of native treefrog, which just means they grow larger, they mature quicker. And so they have a higher reproductive output, which also makes them a really good invader.

SHANNON:
So now we're losing biodiversity on two fronts. Not only are they reproducing faster than our native species, but they're also able to eat up our little native treefrog species because they happen to be smaller and perhaps more delicate and, in my opinion, adorable.

LARA:
Okay, so we know they can negatively impact our native species. And it's not only native treefrogs. They'll eat other like native lizards and other native species. So what aside from reporting them, what can people do if they find one?

SHANNON:
Okay. I'm going to need everyone listening to this podcast to just hold on. This is a little bit of a ride. Just follow me on it, and when we get to the end, we'll tell you why it's important. I am going to—and I think, Lara, you agree with me—but I'm going to advocate for standing up for our native treefrogs and removing invasive Cuban treefrogs. By “remove” I mean “humanely kill." Lara, do you feel the same way?

LARA:
It's kind of one of the parts of my job that I don't really enjoy telling people to do it. But like you said, in the end it's going to benefit our native species. And it's what we need to tell people to do, so yeah.

SHANNON:
So this is the part that people don't love to hear. And it's not even about the killing. It's how we get there. You're going to have to catch them. There is not any research- supported treefrog poison. There's not any legal means to poison them. You have to catch them. You can do this with a net if you really, really want to.

But the easiest way is to put on some rubber gloves or re-use an old plastic grocery bag, turn it inside-out on your hand and just grab the guy right off the wall. They don't usually hop away too fast, so it's not terribly challenging to catch them, especially if they're hanging out around your porch light. So now you've got this treefrog.

Hopefully in a bag that you used to catch it, but you have this treefrog. What do you do with it? How do we kill it in a way that causes the least amount of pain, which is what we mean by humanely killing them. We are trying to do so in a way that doesn't harm them unnecessarily. And the best way to do that is you put your treefrog that's in your bag in your refrigerator for 3 to 4 hours to kind of put them to sleep.

And then once they're asleep and they're numbed out, you move them to your freezer for another 24 hours. And it's at this point that clientele usually laugh at me and tell me, “No, not gonna happen.” (LAUGHS) But really, it's not that bad. And so some of our really proactive Cuban treefrog citizen scientists, they have like a dedicated Tupperware for this or a drawer in their fridge and in their freezer. That is the only thing in force that separates treefrog issues from food.
And I think that's a very smart idea. Definitely don't have any cross-contamination between wildlife and your food. If you have a refrigerator or freezer in your garage, highly recommend using that instead of your kitchen one.

LARA:
Yeah. And maybe put a Post-it note to remind you that you put your frog in there because they might still be hopping around for a little bit.

SHANNON:
Yeah. Make sure they are secured. This is also a great time to go ahead and put a timer on your phone or on your computer reminding you to move them to the freezer. After they've been in the freezer for 24 hours, your treefrog is dead. And so you don't have to take it out of the bag. Just take the whole bag and throw it in your normal garbage.

It doesn't go in the composting bin. It doesn't go in your veg piles. It's not vegetation. Just take the whole bag and throw it away.

LARA:
You guys can do it. I promise you can do it. And especially like Shannon said, if you have kids or grandkids who love catching frogs, just, you know, as long as they're making sure they either wash their hands or we really recommend having some form of protection between your hand and the frog when they capture it. You know, it's something they would love to do if it's not something you would love to do.

SHANNON:
Yes. And it's a great teachable moment for kids, too, to talk about balance in the ecosystem and invasive species. And while it might make some kids uncomfortable, be okay with it. They don't all have to capture frogs so that you can kill them. But the ones that are a little bit more advanced in their wildlife ecology, it can be explained that this is to help our native species. We want to make sure that if kids are participating in this, they know the reason they're participating.

We're not just killing frogs to kill frogs because that's terrible. But if you've properly identified it as a Cuban treefrog, this is how we recommend helping your local Florida ecosystem. Okay, so I was a little bit morbid, but we do have some research that suggests that in areas where Cuban treefrogs have been removed from the ecosystem persistently over time that native treefrog populations may be able to rebound from that.

And Dr. Johnson agreed. He said:

DR. JOHNSON:
If everyone in the neighborhood managed Cuban treefrogs in their yard, they could really have a big impact.

SHANNON:
Which is great to hear. And current research suggests it is working. Let's move on to something that's a little bit more uplifting, and that is the species that we’ll be helping protect by removing the Cuban treefrogs. So could you tell us a little bit more on some of those species?

LARA:
If you're a frog lover, which hopefully Shannon and I can convince you to be, but we have tons of super cute native treefrogs. Not only are some of their names really cute, but the barking treefrog,

(BARKING TREEFROGS CALLING)

they’re just these little plump frogs. And then we have the pine woods treefrog.

(PINE WOODS TREEFROGS CALLING)

There’s the spring peeper

(SPING PEEPER TREEFROGS CALLING)

I mean, love him. Does it get any cuter than that name?

But then green treefrog,

(GREEN TREEFROGS CALLING)

which is probably one you're likely to see out in a more natural area. And the squirrel treefrog.

(SQUIRREL TREEFROGS CALLING)

So we just definitely want to do what we can to help protect our native frog species and the critically important roles that they play in the ecosystem.

SHANNON:
And like the Cuban treefrog, they have a wide variety of colors and patterns, but you can learn how to identify them with a little bit of practice. And one of the cool things about treefrog identification or rather all frog identification, you can learn how to identify these frogs by sound. So, yes, a fun thing. Yeah. And we'll include links to the treefrog calls in our show notes.

LARA:
I'd say that's probably one thing, somewhat similar to birds, is you can, you're more likely to hear a variety of treefrog calls than you are to actually see them because they're so well camouflaged. I guess one more thing to kind of wrap up on why it's so important to protect our native frog species is, like I mentioned, they play a really critical role in our ecosystems.

Shannon and I like to think big picture with any time we're talking to you guys. And they are a key piece in the food chain, not only are they a major source of food for wildlife, but they help to keep insect populations under control. So I think we can all probably agree that we like that. And then even like the tadpoles can help to keep our waterways clean. They feed on some of the algae in there.

There's competition with mosquito larvae. So we you know, nobody, I think, is a fan of mosquitoes. So there's just a lot of things that our native treefrogs do that anything we can do, again, to help protect them is something that Shannon and I are definitely going to support.

SHANNON:
And with that, I'd like to thank everyone for tuning in today. Also, huge thanks to Dr. Johnson for his time and expertise related to emerging Cuban treefrog research. If you're interested in learning more about identifying a Cuban treefrog or reporting a sighting in the Panhandle, be sure to check out our show notes today.

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