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Interview 10:51 - 47:42 Play 10:51 - More
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Cecil Schwalbe, John Burnett  






Frog research discussion, including unidentified voices and area ambiance. John Burnett is wearing the mic.  

Interview 54:37 - 1:25:32 Play 54:37 - More
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Cecil Schwalbe, John Burnett  






Frog research discussion, including unidentified voices and area ambiance. John Burnett is wearing the mic.  

NPR/NGS Radio Expeditions
18 Jul 2002

  • United States
    Pima County
  • Buenos Aires NWR
  • 31.55   -111.54994
  • Stereo
    Sampling Rate
  • 48kHz
    Bit Depth
  • 16-bit
    Equipment Note
  • 2-channel mono. One DPA mic feeding both channels. Right channel at -10dB from left channel.

Show: Arizona Frogs
Log of DAT #: 3
Engineer: Bill Deputy
Date: Thursday July 18

(talk about frog legs, Texas capitalism, cameras, accents)

cecil do you end up doing most of your work at night?

on this project, well.. no, most of this one at night except that we're doing some assessments of the best way to capture tadpoles to determine what species they are and most of that's daytime work. If we are working with the toads or spadefoots themselves, they're mostly active at night but the tadpoles we can use daylight so we can see what we're doing. But this part when we're looking at the adults it's almost exclusively at night, except for occasionally when you get daytime frogs

what do you like coming out here at night, after the rain, in the Arizona desert?

to me, to a biologist, this is mecca, this is heaven, there ar so many things that are coming out, the amphibians, the reproductive ants and termites, and everything's coming out and feeding on them.. the scorpions are running around carrying babies on their back, if you're interested in biology, this ias a fantastic place to come and se what's here, and if you're a photographer it's even more fun. The sounds, the smells, when we were driving in today¿ you know, you could heard that storm. When your'e out in one, sometimes it's noiser than you like, but it's¿ I've been in the desrt now for 30 years, and I feel blessed that I got a job to stay here.

when we were driving in, it was oe of the most beautiful sunsets I've seen in a long long time. Are you still astounded by the sky?

id' just.. it changes every time, it's just absolutely glrius. You get torn. I like to photograph, but that doesn't mix very easily with research, because you're always running someplace to get somewhere breathtaking so I take holidays, and when I have vactation time I go someplace to take pictures instead of data.

where are we going now?

we're on aravokus sienna, which is a part of the b.a. National wildlife refuge, near the town of iraguaoca Arizona, and we're walking to a place called little pond, and it's the only place where we have heard bullfrogs calling this particular summer, because this is the driest summer on record in the city of Tucson in the hundred plus years of existence, and the bullfrogs have just quit calling on other places o the refuge chart, we've been marking thing.. and we think because they're sensing this incredible drought and they're willing to make much of a reproductive adjustment on a year as dry as this one was, but the ones here have been calling so we're going over to see, and maybe record some sounds and get some idea of how many males might be calling

14:22 (14:44)
I think some people would be surprised that there are scientists studying frogs and toad sin the desert¿ because you think of this arid environment and you've got to go to a moist environment like a rainforest to do the best work on amphibians.

I totally agree with that, I didn't realize until I was a graduate student here quite a few years back when I was trying to look at the diversity of different types of animals and it's known that Arizona has a fantastic number of birds and reptiles, but I started looking at amphibians, and it turns out that Arizona, known as a dry states, has 30% of all the frogs and toads in the united states.

Why is that?

15:27 CS
it's because they have this cadre of desert adapted species, a bunch of the spadefoots and toads which we're going to be possibly even seeing some tonight, and they have learned to adapt to these arid conditions, and they'll stay underground 10 months of the year, and when the rains start they will come out and do their breeding and feeding, dig back underground and wait until the next summer.

18:54 JB
so as we're walking along this path right now we're walking over the burrows of frogs and toads?

16:01 CS
Yes, in fact Dennis just actually caught one

16:08 JB
what are you holding in your hand?

16:09 CS
this is a Mexican spadefoot , the one that we heard calling when we were recording the sounds of the storm this is the one that sounds like you're running your fingers down the teeth of a pocket comb. And smell that, what do you think it smells like?

16:25 JB
fx - sniffing
an old cigarette

And old cigarette, But how about almonds, this is one of the spadefoots, you identify it by picking it up and sniffing it, not licking it, but sniffing it and if it smells like almonds that is characteristic of the Mexican spadefoot. This animal has already been out today, and it's not raining any more. Obviously we had a light rain before we got here but that's enough to bring these desert adapted toads and spadefoots out, looking for a meal and if it rains harder they would have breeding aggregations, we heard a couple of them when we were recording the thunder. If you handle those though, you don't want to rub your eyes, and if you rub your nose you'll start sneezing. A lot of people think they're allergic, but actually it's a specific reaction to the toxins that they carry in their skin. One reason these amphibians are so successful they have these antibiotics in their skin. Here's an animal that has to stay moist to stay alive, and these ones living in these hot environments - and what do you get when you have heat and moisture? You get molds and fungi growing. They use great polypeptides and things..and chemicals in their skin to keep them from getting fungi and bacterial infections, you just don't find frogs or toads that have sore because they deal with that kind of injury very very well.

are there predators out there in the desert that eat these amphibians?

there are. There's a lot of the snakes will eat them, some of the spadefoots that we find here occur further east in the states, in the grasslands, and I think the hog-nosed snake is a fog specialist, it's got a specialized vertebrae that is used or pop toads. The defense mechanism that frog and toads use when they're grabbed by a predator is to inflate with air to make themselves too large to swallow. And so the hog nosed snake just starts swallowing it down and all of a sudden all the air goes out of the toad, kind of a neat little trick. Some of the toads are so toxic, these polypeptides, this chemical protection that they have against fungi and bacterial protections can also be used to deter predators. And the Colorado river toad is this great big toad we might see as we're walking along, there are several dog deaths every year from dogs that try to bite these toads, and they succumb. Once those toads get to the adult size there's almost nothing in the desert that will eat them, so they live quite a long time.

19:45 - 22:08
"walking without talking" - mostly just John's breath.

22:08 JB
so are all the amphibians surviving the drought okay?

Well we don't know, we don't have good numbers of.. any that went in.. one of the objectives, we have two projects going on here right now relative to amphibians on the refuge, and one is to look at the bullfrog, this introduced predator, and the effect it's having on native leopard frogs, and to see what we can do to help the leopard frog ,and the other one is to learn and develop some methods of monitoring these desert spadefoots and toads, so we're in the process of trying to gather some baseline data on how any there are, we can answer that question better this time next year, since we haven't tried to count the numbers of toads last year, we just don't know, so we'll see. Where they've gotten good rains they seem to be in good numbers, and the same species that we expect to se ether is there, right now we don't see a problem but we just don't know.

We're being greeted

yes that is the American bullfrog, introduced into the western us as a potential game animal, or a food source for humans. You had no idea it would turn into the incredible predator on our native frogs, garter snakes, and turtle even. We've got data from studies on another refuge that indicates that it probably eliminated the chirca leopard frog and is now in the process of eliminating the Mexican garter snake. A lot of biologists didn't believe us at firs because they couldn't imagine a frog eliminating a garter snake, which are supposed to eat frogs, but they get to be so big that they can eat the adult male garter snake. We'll end up with a population of old female garter snakes with their tails chewed off

where are we now?

We're approaching little pond.. at Buenos Aires national wildlife refuge, and this is actually a famous bird watching site in Arizona, there are hundreds of birds that come here and people come from all over the united states to come and watch them.

and this is perfect habitat for the American bullfrog?

a bullfrog, about he only requirement it really needs in the hot southwest is permanent water, and in this particular pond they maintain, for the large part for the bird watching capability. It makes it perfect for the bullfrog, and they just are thriving here.

25:25 JB
Keep going?

mumbling, off mic, discussion of other mics, following, etc

we were out here on this refuge about t3 year ago doing some summer reconnaissance, and one of the ponds on the refuge we walked up there and we saw this medium size bullfrog jump and grab and eat a smaller one. And while we were sitting there talking about it, a larger frog came and ate the frog that had eaten the frog. And it just blew our minds, we have a study going oat san bernadino wildlife refuge where we've opened the stoamachs of like 8000 bullfrogs over the years and several times we've found a frog within a frog within a frog. That's one reason the bullfrog is so insidious. And so it has suchan impact on the native species, it doesn't even need a food source, it maintains it's own. It maintains population densities 20 to 30 times higher than naything in the scitntific literature back in the natural range of the bullfrog. We use the term biological bootstrapping, it basically maintains it's own population by eating the kids. We should try that at home perhaps?

27:20 JB
species¿yeah¿ are these bullfrogs giving mating calls or territorial calls or both?

that' the mating call, the advertising call fo the adult male that sets up a calling territory and the females come and cchooose the males that they want to breed with. In large populations they start calling back in fortha dn start responding to the others. It's quite a vibrant sound, I grew up in texas, and it's native to texas, and it just could not get across the wstern desert on it's own, it basically could get to central new mexicao and then humans in the late 19th century starting transporting him took him out to san Francisco in 1828 and Arizona in the 1920's and since then the bullfrog has expanded on it's own. One of the things we're doing on the refuge is marking the bullfrogs on some of these breeding sights, and when the summer rains come, we're trying to visit ponds that were dry before the rains to see who far the bullfrog can move to, it's actually been shocking to us. Two years ago we found that they moved over 3 miles within a couple of weeks once the rainstarted and that's about twice as far as we thought that they could have done from prior observation. It just means it's more difficult to set up a buffer zone for bullfrogs because they can move that fast

29:00 JB
what are y'all going to do tonight?

tonight we're going to get a feel here of how many frogs are calling and uh this is one of the few sites, the only place on Buenos aires national wildlife refuge where bullfrogs are breeding now, this is an eastern arm of the refuge, disjunct from the rest of the refuge, and there's still some private lands close to the refuge where the bullfrogs still abound, so we're nost spending a lot of effort here trying to eliminate the bullforg because it would just move in from adjacent lands. So we're going from here to look at places just off the frefuge where we've arranged with some of the ranchers to mark their bullfrogs to see how far they've moved. So we're going to try and atch bullfrogs that dennis, erin, and brent have marked over the last few weeks and see if we can find some that have been marked, we cn see how far they have moved and from where.

so you all are going to try and catch these frogs we're listening to?

not here, not the ones we're listening to because these aren't the marked ones. We're going to places wehre the frogs won't be calling yet, because they're usually dispersing. And these are often the younger frogs, not the great big ol adults, the calling males like this, because we don't believe they disperse that far because they've found their home. They're the king of the hill, so we're goin to be looking for the footsoldiers.


tonight, we're going to go here. We just hadn't been here to assess, just get some feel for so you can see what they sound like calling here in Arizona.

we're all finished now we can go home..

(talking about mics, headmics)

I think we really need to hear, in real simple language, why is this bullfrog a problem to everything else that's alive here?

the bullfrog is only recently, in the last couple decades, only in the last couple of decades that we would come aware¿


we only recently have become aware of the problems that the bullfrogs have been causing in the west. In the 1980s it was the first time in Arizona that we realized the bullfrogs.. Wherever we found bullfrogs that we never found the native leopard frogs, and then we found that some of these garter snakes and mud turtles abounded in similar water ponds elsewhere were disappearing or declining where the bullfrogs occurred, and since that time almost every state in the American west have had problems about bullfrogs coming in and eliminating the native species so it becomes a conservation problem for places like national parks and refuges that have historically tried to maintain and preserve the native ecosystem.

tell me how amazing eating machines the American bullfrog is.

the bullfrog is one of the most amazing predators we've ever run in to for it's size, in Arizona in the last 15 years, we've found vertebrate class that occurs in southern Arizona we've found in bullfrog stomachs, frogs snakes lizards turtles mammals, rodents, bats, it's just amazing in southern Arizona the most common vertebrate stomachs is other bullfrogs. One of the ways that a bullfrog takes over an ecosystem, is that it doesn't need a native population to prey on necessarily, they can just cannibalize their own young and maintain extremely high population densities. The populations of bullfrogs of some of our study sites in Arizona is 20 to 30 times the numbers of adult frogs there that they have an any population that they've measured in native range of the bullfrog, so the bullfrog maintains itself on it's kids, basically.

so should we be hearing the sounds of more living things in this pond tonight, but has this bullfrog eaten it's neighbors?

basically here the aquatic frog that is native to this area, that was here historically is the chiracow leopard frog, but it hasn't been found in this part of the creek in over 20 years, and the Mexican garter snake used to occur here, and the Mexican garter snake has not been seen here for 25 years, we did catch one individual this past summer which tells us that there is some in the neighborhood but they are not able to maintain a population here, by spending some time here and some effort here, and by looking at what's here, we are learning some effects of the bullfrog.

you've gota reputation of the bullfrog hit man of the west.. why do you have it out for frogs? Is that a car. What have we got here?

that's the culprit

normal sized?

it's a mall adult, probably about 250 grams, it's an adult male, in the male you can see the tympana on the eardrum in back of the eye it's always larger than the eye, in the female they're always the same size.. and you can look at the, actually it doesn't have much of a dark throat, probably yellow, usually they have a duskier or yellow throat, in the daylight it may appear more yellow the headlights don't show it very well. But that and you also have this swollen black thumbs, and they use the thumbs to hold on to the females during mating, which called amplexis for these frogs and toads. They just grab and hang on. Seasonally I put one of my phone machine messages, "the summer rain is here, I'm in amplexis and I'm all thumbs. We're putting out an adult magazine, called "playfrog.."

37:26 JB
are bullfrogs this big of a problem elsewhere in the country, is it just the west? I haven't heard people complaining of bullfrogs.

the bullfrog back east in it's natural range is in equilibrium with the other animals in their ecosystem, and they have things like large water snakes, snapping turtles, more raccoons and things that keep a lot of the bullfrogs population in check. Actually largemouth bass and a lot of the sport fishes of warmer climbs do a good job of keeping the number of young bullfrogs down because they like to eat young bullfrogs. But here in Arizona the bullfrog is not native, and when humans moved the bullfrog west across and into the deserts, that was just the boost that the bullfrog needed, so because it doesn't have any natural predators here and the native species in the West have not evolved defensive mechanisms against the bullfrogs. They're just naïve and the bullfrog just takes advantage of that and snaps them up. There are many things that make the bullfrogs an incredible invasive organism. Because a single clutch of bullfrog eggs may number 20000, our native frogs may have 2 to 3 thousand, so that's a ten fold advantage just in the numbers of eggs, bullfrog tadpoles are so unpalatable that some fish will choose to starve to death if that's all you offer them. Yet the leopard frog tadpoles here are delicious to everything, so the bullfrog comes equipped with all these adaptations that make it a scourge when introduced into a new area. But back in the east, it ranges from Canada all the way to Florida, from the Atlantic coast to central New Mexico in it's native range, and it's not a problem there because the other species that prey on it keep it in check, it's another example of an exotic species, and we consider it an exotic species because it's natural range doesn't extend this far, and when you move a species not native into an area into an area that has certain characteristics like this bullfrog it can just take over and eliminate many of the native species, throughout the west, including up into Canada, Europe, it's in France, I went to Japan to visit a few¿ two summers ago, and the most common amphibian or reptile that we saw or heard in Japan was the American bullfrog. We heard the American bullfrog calling while we were on a loggerhead sea turtle nesting beach. So it's just an amazing machine, I get emails from central America and Europe every month on what they can do to solve their problem. And we're still trying to figure out what to do, it's not simple at all.

so in a way it's like the fire ant of the amphibian world

it's exactly.. the fire ant, the kudzu, the plant that's taking over the southeast, purple blue stripe, the plants and animals are leeching, they're coming in and taking over because the organisms there haven't learned how to deal with them. It's a huge problem

40:58 JB
but it's mostly a problem to conservationists, it's not a problem to home owners or city dwellers, is it?

41:05 CS
well city dwellers probably not, a lot of people say, does this mean that life on the earth is going to collapse? No, it probably won't, but it means that the composition ecosystem will probably change. In fact I've dubbed this era that we're in the homogocene, the period in which you have all of these communities become the same, you'll have bullfrogs and English sparrows, brumgrasses, and you'll have all these things that they get along, they're good invasive species, and they'll still be producing biomass but whether or not the other species in that are can use that biomass remains to be seen, and that's why we're going into simpler ecosystems, not quite as divers, and from my perspective that' a little bit risky. The value of diversity, basically the genome, we haven't explored all the values that's there - medicines and things, the toads and things that we've talked about tonight, there's a lot of medical applications there, many parts of the rainforest that we haven't explored all those values yet.

42:34 JB
Someone who is not familiar with the complexity of the problem you're describing would come out here in this warm humid night in the southern Arizona desert would hear these crickets, hear the bullfrogs, and would think 'what a wonderful pastoral sounds,' but when you as a biologist hear these sounds, what do you think?

30:35 CS
I thought the same thing when I cam here, I actually grew up in Texas, where I hunted bullfrogs as a kid, loved to eat them, still do, but went I became an ecologist and started looking at the effect of these invasive species - not just the bullfrog - but the cray fish is a predator that's being introduced here and it's also amphibious in that it can move across land at water and it's starting to get to be a problem here.

43:30 JB
just the bullfrogs right now

31:18 CS
now that I know what it represents, I first got involved in the problems the bullfrog created was when I worked with Arizona game and fish back in the 1980's, and it was quite new concept and since then corresponding with most of the western states, we view it as a serious problem for native populations, I can't argue with people to say 'great, It's great to have some frogs here, I'd rather have bullfrogs there than no frogs at all.'

44:19 JB
is this the sound of the enemy?

44:21 CS
this is the sound of the enemy. It's kind of ironic, here in Arizona the only frog that makes a chirp when it jumps into the pond is the bullfrog, just kind of a neat little sound, when it takes this little myeeck, when they would jump in. now I know when I hear that Myeeick I know it's the enemy, because the leopard frog would jump in there but they don't make a sound. And now whenever I hear the bullfrog, since I've heard it now in half a dozen countries when I've traveled around it's becoming quite pervasive, and it's difficult because the ability of the bullfrog to move across the land in the rainy season is legendary.

45:13 JB
you believe this bullfrog can travel as far as seven miles?

45:17 CS
we have data from out here at Buenos Aires, we believe that they move 6 to 7 miles over the course of the summer into the fall, we don't have.. that didn't come from marked frogs, we can't say specifically that this from will move from this point to another, but at the time we discovered that frog, there were no breeding populations of bullfrogs within 7 miles.

45:47 JB
to 7 miles per summer.. that's a pretty remarkable amount of hopping

45:54 CS
it is. And that's in a summer season, actually even more astounding is the amount the initial movements between ponds. What the bullfrogs do is hop from pond to pond, I think they can probably smell the ponds, not the water, but probably associated vegetation, and they go to them, and they can go as far as two miles in a night - and they went 3.1miles just in a matter of a couple of weeks. The 6 to 7 miles.. that was over a four month period, so it probably had to work it's way through several ponds, actually a fascinating apart of the research now is to see how they get to different places and from different places, we're going to go out later tonight and try to measure some distances on frogs that we've marked form earlier this summer.

when do you want to get just the sound of the frogs? Where are they going to start looking?

(talk about moving, driving, mosquitoes)

49:00 - 53:15
ambience, frogs calling and crickets

(discussing mics)

that'a young one, just go down and grab it's tail, you'll be okay.

you're in the car all by yourself, you're fine

look at thae big bullforg out there, not a big one.. but

oh yeah, you can see it's mouth and it's eyes

that'a female because of it's white throat. What a cutie, that's a youngin.

relax, he'll move on it's own¿

is your equipment skunk-proof?

I'm sure it isn't

I once had to shower off with tomoto juice at summer camp. Sort of a rite of passage.

is she gone?

look at that skunk took over our camp when we left. We came back and it was lapping grease out of our skillet!


cecil is this a big male or a big female down here. No no there's another one down here, I've got my light on it right here. It's back is to us. There's another one, no I'm looking at another one right here.

it's hard to tell¿ you can't tell from this angle unless you can see the ears. And those ears look big so I think those are males. You can only hear a handful of them but look at all of them that are here.

56:41 JB
I mean we're looking gat this one little small area of the pond and there's 1, 2, 3,

56:59 JB
you don't have to have that many bulls to keep things going.

57:14 JB
they're not moving at all they just kinda sit there.

well they're sit and wait predators

yeah that's that duckweed isn't it. oh I see they're waiting to eat, ah so that's why they're so immobile

you a fisherman?

not to speak of

my dad and I caught 9 bullfrogs this big or bigger on a stock tank in texas by taking these top water lures and you wiggle them a little bit and the bullfrogs would swim close by and the nest time you wiggle it the bullfrog would jump on it and try and shove it into their mouths. It was incredible to watch.

58:03 JB
what's that little bass kind of a (sound effect)

58:07 CS
that's just kind of a little

58:09 JB
that's the male too?

58:10 CS

58:15 JB
kind of an exclamation part, a belch after they've made an oratory.

58:35 CS
that's a release call¿ or is that dennis? That's pretty cool¿

58:45 JB
make it do that again!

release call

release call

we're going to get letters on this!

59:03 CS
you don't have to air it! one of the ways we catch snakes, that was a release call, and most frogs have this call when they're captured, and if you hear that in the wild and one of your friends that have caught them, you look around quickly because a snake usually has caught the frog, and you've only got a few minutes to get it before the snake swallows the frog, and once it becomes muted you know the frog has been swallowed and continues to call, so really it's a fun way to catch snakes.

59:47 JB
and they all have the same markings? All over the world?

they're highly variable, some are leopardy looking, we've got bronze ones with no stripes.. I have a picture of a bright yellow one

1:00:03 JB
it all adapts to it's surroundings?

it's not necessarily cryptive, it's in the genes. We're going to have a pop quiz, what gender is this?

well lets see, that would be a male? No wait. You said when it's larger than it's eye, it's a male

it's about the same size, a female

the tympana

the tympana, the eardrum. And the white throat, we saw that female out there staring at us, we could see the white throat - the males are yellow, and the yellow's not showing in our headlamps but it's a right yellow during the day. But that was pretty neat, that was kinda singing a song.

they don't squirm much

well that's because they're playing opossum.

oh is that it?

as soon as it knows when you don't have control, then all of a sudden it's gone

try it


this one is being pretty passive

fx - frog slips away, laughter

is that duckweed in that?


I think that skunk was chasing that frog - I heard it freaking out over here

at the nighttime surveys at shoal creek, the creekfish and the green sunfish ahad staked out the creek, and they were in a huge grid¿

1:02:26 JB
mosquito fish

1:02:37 CS
boy that skunk was pretty cute

1:02:44 JG
what do you call that green stuff over there?

1:02:46 CS
It's kind of a cosmopolitan plant, especially in the tropical

1:02:57 JB
is it working again??

1:03:02 CS
it's real thick, and that's because¿(fades out)

I just love being out at nigiht¿ I see the most interesting biological phenomena. I just love going out when it's humid. Because desert animals don't move around a lot when it's not. They're waiting for this, because it's too great a water cost to move out oon a night just two weeks ago because there's such a water deficit

1:04:36 JB
the bullfrogs live out in the open all year?

1:04:45 CS
they'll use burroghs, and in the winter, it's cold enough they disappear the months of November, December, January, and February. Sometimes in march. Dennis what's the earliest you've seen them.

1:05:03 D
I've seen them fairly early when it's warm. They'll be out.

1:05:05 CS
we've actually seen them in February. Sometimes..

1:05:08 D
numbers are usually pretty low

1:05:09 CS
and they're pretty lethargic, they don't move very well.

something about the smell of a humid night, just my favorite thing to do to come out during the sdesrt summer rains. I hope we see one big palarudy beetles that hit our windshield¿. Looks obscene to me. (amidst light chuckles)

how many barking frogs did you get to hear last night? You were in one of the high density areas?
no, I was out with brent and ¿ we caught two but we could hear a bunch in the valley, down at the bottom of the hill. I just hope I can¿(off mic)

1:06:56 CS
new barking frogs and they wanted to check out that area of the forest. All we did


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