Reptile & Amphibian Forums

Hello,

I'm pretty sure I've never posted in this forum, but I just got a Japanese rat snake (E. climacophora - is elaphe still the genus?) and that has piqued my interest in them. As an aside I also adopted a yellow rat snake that looks like it's got some gray in it a couple years ago.

Anyhow, in researching the Japanese rat snakes, I read about their egg-eating adaptations (such as blunt extensions of neck vertebra that crush eggs), apparently similar to but not as advanced as the dasypeltis egg eaters. I have found references to another species of asian rat snake (E. davidi) having the same morphological adaptations as the climacophora (Helfenberger and SchÄtti, Russian Journal of Herp, v5, 1) as well as an online reference to E. dione having the same adaptations.

I was wondering how widespread this is in other similar and related asian snakes. Also, have any of you who keep climacophora, dione, or (less likely) davidi observed them eating eggs?

Thanks,

Billy Brown
Philly Herping

Hello, Billy.

I've kept a number of American and Asian ratsnakes, especially the Eurasian, and the egg eating ability is pretty prevalent in ratsnakes in general. Whereas, most Asian ratsnakes will include various eggs in their diet, probably, a lot of American rats won't pass them up either, although it might not be as prevalent, just my opinion. I think the vertebrae adaptation is more common in the more ancestral Asian species, not necessarily Elaphe, thus giving you climacophora, davidi, and others from that area of the world. Climacophora is still in the Elaphe at this time, along with many others, including dione, bimaculata, quatuorlineata, schrencki, carinata, etc. These snakes all will take eggs, some more readily, but the projections, as an adaptation, is more obvious in some than others. I've kept mostly dione, bimaculata, and schrencki, and have seen all these eat eggs, and swallow them shell and all. You can see the mechanism at work.

Other ratsnake types, in genera like Gonyosoma and Coelognathus, etc, also have this adaptation.

I believe this is an aspect of ratsnake biology worth studying.

Terry

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Ratsnake Haven...researching ratsnakes since 1988

Ratsnake Haven Group...an information providing list site.

Thanks Terry,

I read Gans' 1952 article about climacophora on the American Museum of Natural History's digital library (http://digitallibrary.amnh.org/dspace/handle/2246/3997 the server seems to be down right now but I think that's the link), and in it he also commented on carinata having similar modifications of the vertebra, but that in carinata they actually pierce the esophagus. I'm trying to learn more about that too.

The pantherophis group seems to be in a totally different bag, though, eating eggs whenever they get the chance, but opening the shells by digestion rather than crushing them in the throat. Interesting also is that the pituophis eat eggs and use a third technique: pressing their bodies down against a hard surface while swallowing.

I'm trying to get my hands on Helfenberger's paper on European and Asian elaphe and ex-elaphe because, as I understand from the summaries I've read, he uses vertebral similarities/differences as a basis (among other factors) for grouping or distancing the species.

I agree that this is fascinating stuff. I think by feeding snakes so exclusively one type of food we miss out sometimes on some really interesting behavior.

Cheers,
Billy
Phillyherping

Billy, very interesting behavior.

I've seen eggs eaten by bimaculata, dione, and schrencki and they crush the eggs in their throat, but I've not witnessed it with other species. There might be some racer species that have this behavior also. Have you heard how ratsnakes sometimes flatten their throats/necks vertically, and some species, like in Gonyosoma and Coelognathus, even have special pouches that they can inflate with air making their necks larger and certain spots look like "eyes". I'd love to read more.

Later...TC

Mine love eggs. I use quail/cockatiel eggs to coax my stupid male out of his persistent winter fasts (the female is more like a cornsnake... if I dangle it in front of her she'll eat it. The male is a little more typical for his species...)
It's quite interesting to watch. They swallow the egg, and then in the early esophagus (I think it's C18-36 that has the spines) it halts and they start squeezing until the shell breaks. A few such squeezes and the eggs have shrunk down quite a bit (a cockatiel egg made about a pinky-sized lump in him when he was small) and is swallowed.
My north american ratsnakes will also quite happily eat eggs, but they just eat chicken eggs whole. No cracking or anything. That's kind of fun to watch them get them in their mouths.

I think the North American ratsnakes, at least the Pantherophis group, are much more evolved than the Asian species and have lost several adaptations or archaic structures, including the vertebra for crushing/piercing eggs. Now that I think of it, those vertebra structures associated with the egg crushing have been found in several kinds of snakes, not just the ratsnakes, I believe. I think there's a specific name for those vertebrae that I can't recall at the moment.

I posted these on the milksnake forum, but they relate to this thread too, at least as far as being about a closer relative of the pantherophis gang eating an egg. I can't seem to get them in the right order; as they are now it's 2, 1, 3:

Phillyherping

That's interesting. Did the milk swallow the egg whole, or did he crush it first in his throat, before swallowing? I would expect Eastern milks and mtn. kings to eat eggs, and I believe common kings eat turtle eggs and others. TC

I think captive Lampropeltis have more stomach than brains There was that photo on the kingsnake board once of an escaped Cal king who got into her owners backpack and was attempting to eat a plastic bag that had the scent of a pillow case that had been used to hold a rattler... I did an ethology experiment once with ingestively naive mex blacks and cal kings, and they did attempt to eat the snake-scented swabs on at least one occasion.

I dunno. I'm not sold on traits like the so-called gular teeth (I don't know if you'd still call the modified ventral vertebral spines "teeth" in this case, 'cause I've never looked to see enamel as is claimed on Dasypeltis spp.) There's no reason to assume it's basal to all Elaphini and by extension, Lampropeltini. It's clearly a trait that is "able" to evolve rather easily in snakes, as it's cropped up in a few species. I also hadn't realised that other species of Elaphe had it - can you post the reference for me? I'd like to read it

While I'll never defend the brains of milks and kings, and I'll never understimate their stomachs, I do think it's a smart thing to eat eggs when they find them - eggs don't fight back. Please excuse the sloppy citation format.

Gans (Gans and Oshima, 1952. Adaptations for egg eating in the snake Elaphe climacophora (Boia). Amer. Mus. Novitates 157: 1-16) is interesting and free at the American Museum of Natural History's website.

Dowling, Herndon. 1959. Egg-eating adaptations in the Chinese ratsnake, Elaphe carinata Günther. Copeia 1959 p. 68-69. I still haven't gotten my hands on this one, but will soon.

On this website (now down and available cached through Google) I found the reference to dione's adaptations.
http://64.233.187.104/search?q=cache:UvOp2sJu4rwJ:www.nafcon.dircon.co.uk/ratsnakes_elaphe.html elaphe dione egg eating&hl=en

Alex, we're not saying it's basal, just that egg-eating is quite prevalent in ratsnakes. Now we're getting to the point of looking at how many species of the Elaphini have the vertebral projections, or "gular teeth", as you referred to, and that seems to be a more primitive adaptation.

I have a reference to, A Monograph of the Colubrid Snakes of the Genus Elaphe, Schulz '96, p. 51 and 52, under "Prey and Predation".

First, "Elaphe carinata, E. obsoleta, E. schrencki, and E. vulpina show a preference for small birds and especially bird eggs in captivity, this is confirmed by data obtained in the field (MELL 1929a, POPE 1935, RIVARD 1976, BANNIKOV et al. 1977, STICKEL et al. 1980).

Second, "Anatomical studies in E. carinata, E. climacophora and E. quadrivirgata have revealed neck vertebrae (possessing hypapophyses), which are conspicuously curved forward and may be assumed to aid breaking the shells of egg (GANS & OSHIMA 1952, DOWLING 1959, GORIS 1963, FUKADA 1992). HELFENBERGER (pers. comm.) confirmed this adaptation in E. davidi, E. dione, E. quatuorlineata and E. schrencki. While the latter three have forward pointing curved hypapophyses, E. davidi has (similar to Dasypeltis) forward pointing linear hypapophyses (HELFENBERGER & SCHATTI in prep.).

I don't know anything about enamel on the spines, like in Dasypeltis, but maybe some research of literature will bring this up. I know that "hypapophyses" is a characteristic that has been used in taxonomy, especially in the old days when morphology was more prevalent, and it seems to be associated with more primitive species/genera, and possibly the fossil records. It is not exclusive to the Elaphini. I don't have any references right now, except Holman is a good author for fossils.

Elaphe carinata seems to be a more primitive ratsnake considering all its characteristics and I think could be given a separate genus name eventually, in which I would think quadrivirgata and davidi have a chance of aligning with, imho. Also, I would add that I'm not familiar with the vertebral structure of species in Orthriophis, Euprepiophis, Gonyosoma and Coelognathus, but believe they eat eggs and are fairly primitive too. It would be worth looking into, I think.

All for now..gotta run. Terry

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Ratsnake Haven...researching ratsnakes since 1988

Ratsnake Haven Group...an information providing list site.

About those hypopaphyses (I'm glad this is a written conversation because it hurts to try to pronounce that).

I don't think there's anything primitive about the feature (just a downward extension of the vertebra) but that with the rise of genetics, we've got more to go on than physical features to figure out relationships.

Read the Gans article - it's free and easy to access (see the first post in this thread for the site), and in it Gans actually discusses what the white substance is at the end of the hypopaphyses - enamel or just some very hard bone.

What I'm really curious about now is what studies of diet/stomach contents show. Gans mentions that climacophora are apparently known for liking eggs, but I'm curious about the degree to which all of these species eat eggs in the wild - what % of their diet.

Cheers,
Billy

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Phillyherping

>>I don't think there's anything primitive about the feature (just a downward extension of the vertebra) but that with the rise of genetics, we've got more to go on than physical features to figure out relationships.
>>

That's true, but taxonomy is always best when you maximize the number of characteristics you have to look at. So, dna is good, but better with other characteristics too. Also, remember that fossils are almost always bones. Lots of times the scientist is trying to i.d. the snake from a single bone, or vertebra. As far as being primitive, some grous of snakes have it (hypopaphyses) and some don't. Some in a group, like ratsnakes, may have it and others don't, and the theory is that the more highly evolved may have lost it. Of course, that remains to be proven...not my task.

>>Read the Gans article - it's free and easy to access (see the first post in this thread for the site), and in it Gans actually discusses what the white substance is at the end of the hypopaphyses - enamel or just some very hard bone.
>>

Will do.

>>What I'm really curious about now is what studies of diet/stomach contents show. Gans mentions that climacophora are apparently known for liking eggs, but I'm curious about the degree to which all of these species eat eggs in the wild - what % of their diet.
>>
>>Cheers,
>>Billy
>>

Billy, do you have the Schulz ('96) book? In it he discusses the diet of each species. I will tell you there is variation within the species. It depends on what part of the range a snake is in and what food items are most available. It also is dependent on the season. I think bird nest raiding is prevelant in ratsnakes that live in northern regions because of the bird migrations and because birds are nesting when the snakes are most hungry, in the spring.

Fox snakes are big raiders of bird nests in spring because the prey is abundant, but in summer they switch to other prey. It is one of the snakes I enjoy looking for in spring, especially in conjunction with red-wing blackbirds which nest in cattail marshes. I don't think this snake has the hypapophyses either. They could have lost this feature along with some others with the other North American ratsnakes. This adaptation didn't necessarily evolve for the purpose of crushing eggs. That still has to be determined.

Schulz discusses other ratsnakes too that vary in how much they eat eggs. One small island form of quadrivirgata eats birds and their eggs almost exclusively and gets quite large. He also mentions quatuorlineata as eating eggs to varying degrees and that in one area of its range the snakes eat eggs about 95% of the time, but that is seasonal too. Also, remember that eggs are not the most nutritious item. Mice are likely a better food source. I think egg-eating is pretty prevelant in climacophora, but don't know any percentages at this time. Most of the time egg eating is just a convenience, and ratsnakes are quite capable of taking advantage of it.

The direction I'm interested in is finding out how much the characteristic of hypapophyses has been used in taxonomy, and which groups or genera have it and which don't. If you see any more literature discussing this, let me know...thanx.

TC

>>The direction I'm interested in is finding out how much the characteristic of hypapophyses has been used in taxonomy, and which groups or genera have it and which don't. If you see any more literature discussing this, let me know...thanx.
>>
>>TC

I found some references in, Snakes..Ecology and Evolutionary Biology, Siegel, Collins, and Novak editors, 1987. In "Chapter I: Systematics", Samuel B. McDowell writes that Colubrid snakes have posterior hypapophyses in the subfamilies: Homalopsinae, Xenoderminae, Boodontinae, Pseudoxenodontinae, Natricinae, some Xenodontinae, and some Colubrinae.

In the Colubrinae, some have them and others don't. Also, some have them all along the column, and some have only a partial number of vertebrae with them. Colubrines usually only have just keels pointing down too, and not the extra projections. The New World Xenodontines and Colubrines seem to be more advanced, having lost some old adaptations, from the more archaic subfamilies. Natricines branched from the Colubrines early on, likely in the Old World, and have retained the hypapophyses which is a taxonomic characteristic for that group.

McDowell also talks about the dentition in the Colubridae and the fact that rear-fangs and Duvernoy's glands seems to be a primitive condition. This condition is common in the most archaic species, so is also taken into consideration as a morphological characteristic in taxonomy.

There's a nice section on fossils and snake evolution in this book too.

Cheers...TC

Is that a Pueblan? What type of egg is it eating? Quail? Didn't know milks would eat eggs.

reako45