Toxins in Gray Treefrog Metamorphs

[opistoglyph]

Odd occurrence. I was aware of severe toxin levels in stressed gray tree frogs after handling one that had been hit by a car and inadvertently touching my lips and nose a short time later. The result was surreal, and ended with fifteen minutes of my diaphragm spasming like a jackhammer, making breathing almost impossible. I've survived numerous venomous snakebites without antiserum (allergy) but sat at the side of the road embarassed that I might die from accidental gray treefrog poisoning, lol.

I have some ribbon snakes, most switched over to scented pinkies. They are fed toads, tadpoles, treefrogs, even red efts and newts from my own ponds until they switch over. I have some baby ribbons who have tripled in size since birth a few weeks ago eating newly metamorphosed toads, tadpoles and salamander larvae of various species. They are too small to switch over to scented pinkies yet.Yesterday I collected a number of newly metamorphosed grey treefrogs (bright green, tail still evident), and fed them to the ribbons, which they ate eagerly. ALL of them died but one, several regurgitated before death, all were in obvious distress, bodies contorted and twisted up, several died biting their own bodies or the bodies of siblings. These same babies snakes have eaten newly transformed red efts, small redbacks and slimys without any sign of poisoning- ribbons are notoriously resistant to amphibian toxins- and my adults have eaten adult gray treefrogs- but died within hours of eating the gray treefrog metamorphs.

Has anyone out there done studies of toxin levels and/or changes in toxins during the various stages of amphibian development? This could be significant for research medically and ecologically. Also, is this a localized thing? Are our local ribbons susceptible while other populations are resistant? I am loathe to try feeding the metamorphs to larger wild caught ribbons to see if they are resistant. Is it a local effect in the young of our local gray treeforgs?

God, I love nature. Been at this 5 decades and I just find twenty more questions for every answer I get!

[John]

You know, I'd have to go and do a serious literature search for you to get specific papers, but there have been _many_ studies (we're talking hundreds of journal articles) done on amphibian toxicity, particularly in North American species of amphibian. This includes the toxicity of different stages in the life cycles. I'm quite sure Gray Tree Frogs feature in several.

As for significance medically and ecologically, that's nothing new - as well as biological research, there are billion dollar corporations doing drug screening based on natural products that come from everything from poison dart frogs to hydrothermal vent tube worms.

Regarding whether the snakes dying is a local phenomenon, Prof. Edmund "Butch" Brodie Jr has studied in incredible depth another member of the Thamnophis genus on the west coast, and different populations have different resistance to amphibian toxins. I don't have a citation to hand but I'm pretty familiar with his body of work (I've communicated with him several times actually). I don't think it's an unreasonable assumption that where ribbons are sympatric with Gray Tree Frogs they have some resistance to their toxins. That pretty much means you can't use these frogs to feed your snakes without at least some risk.

Butch's research has shown that while the snakes are resistant to amphibian toxins, they are not immune to them. I'm pretty sure metamorph Gray Tree Frogs have particularly high levels of toxins in them as a way to discourage predation of metamorphs leaving ponds. Combine this with the fact that the snakes are resistant rather than immune, and it seems quite reasonable to me that the younger snakes would be more likely to die in your scenario.

On another note, you're probably not going to win any friends here by posting about feeding amphibians to snakes. After all, this is a forum for people who keep amphibians as pets. Ribbon snakes certainly don't need to eat amphibians - they will eat insects, and insects are a heck of a lot more abundant than amphibians. So don't be surprised if you get some unhappy responses on this topic.

Best,

John

[opistoglyph]

Thanks for the fast response.

No I realize I won't win friends with this, but I've devoted acres of my land to local wildlife, including introducing colonies of local amphibians, and I keep a few dozen species of amphibians as well. I only feed the amphibians (from my own ponds, not wild caught) to snakes that haven't been switched to scented food yet, and have fed plenty of small abundant captive born local snakes to my larger amphibians, so it evens out. I even witnessed a large bullfrog make the mistake of grabbing the head of a big watersnake that was swimming by with only the head visible. Boy were THEY both surprised!

Just like frogs. You can't buy Purina Snake Chow, they gotta eat what they eat..

Reminds me of people calling me to complain about a hawk at their bird feeder eating their birds. First of all, not YOUR birds, second, a Hawk IS a bird. You've constructed a food chain, lol! Third grade, 101.

Mostly posted out of curiosity as to whether others have noticed this kind of toxicity variance in various stages, and also as kind of a warning. Until I got a concentrated dose of stressed gray treefrog poison in me, I had NO clue they could be that toxic- I've handled them for years without any serious effects. I'm usually more careful.

[SkeletalFrog]

It's just a poster from a meeting, but this might be what you're after: Comparative Peptide Profiles of Sympatric Anurans Hyla versicolor (Hylidae) and Lithobates clamitans (Ranidae): An Anti-predator Hypothesis

The above study was done with adults, but this study compared palatability between species, and found most amphibians tested would eat H. versicolor tadpoles with no reported ill effects.

Another possibility to consider - could that pond containing the tadpoles have been contaminated with anything recently? Given how you describe your land, my reflexive suggestion is local kids sneaking out there at night and accidentally/deliberately dropping something into the pond.

[opistoglyph]

Thank you for the links!

On the possibilty of pollutants, kind of slim. The amphibians in the pond, plus the uneaten metamorphs from the cage are all acting healthy. Plus, people sneaking on MY property? I was the biggest breeder of venomous snakes in the northeast for 20 years. Everyone around here is convinced that I keep stuff running around loose in my yard (don't know WHO would start rumors like that!) for protection. When I had the big mammals and valuable birds, I had a perimeter fence, now I don't even need one- paranoia does the trick. Scared neighbors are good neighbors.

No sign of illness in the one survivor from that group of babies, or other babies from different groups that didn't eat yesterday. I might try a couple of survivor metamorphs on a couple baby watersnakes and see the result- which wouldn't be conclusive being a different species and all, just interesting to note..

[LilyPad]

Why would you continue to "experiment" and kill off more snakes when you saw the results of the first round? I'm not a expert in reptiles and amphibians, and I agree that it is odd you would post this on a forum where frogs are beloved pets, but just coming from a rational, common sense standpoint, why would you want to kill more snakes in such a traumatic way?

[opistoglyph]

These same snakes, had they not been born in a cage in my collection, would have been born on my property and eating the same foods. Observation wise, it would be interesting to note whether the same toxicity problem is noted in Natrix in the same location as the Thamnophis. Both Thamnophis and Natrix have dozens to a hundred young apiece, and 99% die in the wild in their first few weeks, much like amphibians.

And when do the toxin levels change or drop? Or the tolerances of the predators build up to suitable levels? The whole concept that amphibian toxins change at various stages is brand new to me after 52 years in this field, and I'm willing to bet others that read this may find it interesting. Much less the fact that a severely road injured gray treefrog could pump out enough toxin to incapacitate a 200 lb man capable of surviving black forest cobra bite without antiserum, (plus the other nasty effects I had from it).

There have been many recent years when both ribbons and watersnakes had very low populations, most had presumed predation by night and blue herons, much like half the turtles in the US that are disappearing, as well as many amphibians. These birds are at pest levels now. If the problem actually relates to a change in toxins in young treefrogs locally, it certainly would be interesting to note it. This is not the first time I've raised these species and fed them wild caught food before they got large enough to switch over to scented pinkies, and I'm almost certain gray treefrog metamorphs were in the mix, so this is kind of interesting to me and local wildlife people. Our state people know almost nothing about amphibians or reptiles.

I have entomologist friends who object to my feeding insects to my amphibians as well, including species thought previously to be toxic that are accepted quite well. I know many amphibian people who feed pinkie mice to large salamanders and even larger mice to various frogs (though they are not acceptable as a regular diet item and may be bad for them, the hobbyists often brag about it). Many people like mice. I know many people who feed feeder fish of several species to amphibians. Many people like fish.

Wasn't looking for sympathy or approval, just intellectual dissemination. I see pictures of people with treefrogs on their faces, handled by their children, and think back to my stressed gray treefrog accidental toxin ingestion and shudder. If the young are more toxic or have a different toxin, that might be handy for hobbyists to know. Some keepers of aquatic salamanders load their tanks up with tadpoles for food- might save them a loss of a valued specimen. Likewise, a lot of reptile enthusiasts are also members here, and it might be a cautionary tale for them as well.

And lastly, the few specimens of extremely numerous amphibians and reptiles Iwould sacrifice in the pursuit of this knowledge are nothing compared to the deaths of thousands of larval amphibians kept and raised by hobbyists who have never bought a water test kit or studied filtration or understood oxygenation of the container and population dynamic who are thrilled to have a few specimens survive while hundreds died needlessly. Studying toxic animals, breeding endangered species for zoos and release programs, designing release programs and captive colonies is what I do, and sometimes you gotta break a couple eggs to make that omelette and understand all the variables.

Sorry if I offended you in any way.

[Rae]

Why would you continue to "experiment" and kill off more snakes when you saw the results of the first round? I'm not a expert in reptiles and amphibians, and I agree that it is odd you would post this on a forum where frogs are beloved pets, but just coming from a rational, common sense standpoint, why would you want to kill more snakes in such a traumatic way?

Glad to see that I wasnt the only one wondering this ... but I had no idea that Grey tree frogs could be poisonous.

[SkeletalFrog]

Knowledge for its own sake is generally worth it. Pretty much all modern medicine and technology can be traced back to "I wonder what happens if I do this?" For all we know, these could be a parallel system to the Brodie's garter snakes, which have already increasing not just our understanding of evolution and ecology, but also yielded novel insights about sodium channels in neurons, which in turn has countless medical applications.

Opisthoglyph, personally, I'd actually hang on to those metamorphs, with the goal of breeding them and actually setting up an experiment with proper design and enough statistical power to quite possibly be publishable. Maybe get several dozen ribbon snake litters next year, and randomly assort them into groups that are fed the offspring of these metamorphs, some wild-caught tadpoles you gather next year (both greys and other species for an additional control), and some wild-caught tadpoles from a different location many states away. I'd also freeze some tadpoles for chemical assays (I suspect the author of the poster I linked to would be keen on doing some of the chemistry on such a potent toxin).

The number required is tricky, but with some clever stats could probably be reduced. Unfortunately, this is a perfect case for non-parametric statistics, which I'm not particularly familiar with.

Still, I'd save those metamorphs, as their offspring could be a key to determining whether these are inherent toxins like toads or acquired through dietary sources like dart frogs.

[opistoglyph]

Thanks. I was almost loathe to say that I went out and collected some for the state wildlife pathologist- I've intellectually stimulated him here and there a few times over the years. There is the possibility that my man-made ponds, though the soil on my property is nearly identical to that in vernal pool areas and woodland ponds locally may also have introduced an element that has influenced this...

My toxic hero, Thomas Eisner (an entomologist/toxicologist, but a good Cornell contact to get things to the right people) has passed away, as have many of my capable friends over the years, but the state wildlife guy loves a mystery. The negative side would be allowing state guys on my property to do collecting <sigh>.

I brought him chytrid infected frogs four summers ago when it hit our area first time. He asked me how I found them and deduced what they were suffering from. I said that I saw adult green frogs hopping around in the sun on hot roads during the day acting disoriented and spastic (for the first time in my life). I assumed that since the fungus irritated the skin in early stages, it had the effect to make the frogs spread the fungus this way, traveling to new ponds, DRIVEN to new places, much like rabies causes the infected animal seek out another victim. After testing, yes they were infected, but I seem to be as yet the only one who has noted this phenomenon. Though chytrid has now moved through twice in this region, populations generally bounce back in one year, so I am assuming some level of resistance in individuals. I read about it constantly, provide specimens when I can.

Always new things. Too much to learn, but fun while you do. I'm sure you would laugh, but I was shocked to find out after years of keeping and breeding caecilians, that many of them have strong toxins- none of the literature I had read mentioned it. And yet I have several species of snakes that eat them (all of which readily switch to scented substitute prey items- much like mud snakes will eat a sponge rubbed on an amphiuma, or a rainbow snake would eat a rock with eel mucus on it- young ribbons aren't that easy to switch until they're 12" plus) and again wonder about that predator/prey relationship- acquired immunity? genetic? fascinating.

A pleasure corresponding with you, you've given me much to plan and consider. My facilities are not sufficient for this type of work, just observational. I do captive breeding. If no one can breed it naturally, I do. If people can't keep it alive, I do. Bugs to birds, not attached to any one group or species, I find them all worthy of the effort necessary to help others work with them and save them for future generations.

[Jennifer]

Hi, i was reading what you were saying about the toxins on the grey tree frog. I caught a grey tree frog in august and kept it as a pt. About two days ago i came in contact with the toxins on my lips. They have been burning for two days now. It is quite uncomfortable. I have no other symptoms. Any opinion about what i could do? Is there something natural i could rub on or eat to stop the reaction? Its kind of scarey because i do now realize the severity of handling and owning this tree frog now.

[Shiro]

Go to the doctor. If it's been burning for two days, there is something wrong and it needs treated.

[Jennifer]

Thank you