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?