My early Christmas present: a dead corn snake
December 18, 2014
A friend’s daughter owned a pet corn snake, and a hamster. About a month ago, the former got into the latter’s cage — and in a reversal of the usual course of such events, sustained some nasty injuries. As snakes often do, it struggled to recover, and the wound seems to have necrotised.
This morning I got an email from the friend saying that the snake had died, and asking whether I would like it. I managed to restrain my enthusiasm for long enough to express condolences to the daughter; and an hour later, the snake was delivered!
Here it is — as with all these images, click through for the full resolution. I’ve learned that it’s difficult to measure the length of a snake — they don’t lay out straight in the way that you’d like, even when they’re dead — but as best I can make out, it’s 120 cm long. It weighs 225 g, but don’t tell Fiona I used the kitchen scales.
The hamster wound is very apparent, just behind the neck, on the left hand side. Here’s the head and neck in close-up:
Ouch — very nasty. It can’t have been pleasant watching a pet linger on with a wound like that.
He (or she? How do you sex a snake?) was a handsome beast, too. Here’s the head. You can easily make out the individual large scales covering it, and make out some of the shape of the skull.
The skulls of snakes are beyond weird. Here is one from an unspecified non-venomous snake at Skulls Unlimited (i.e. probably not a corn snake):
Hopefully at some point I’ll be able to show you my own snake’s skull. In the mean time, this guy says he has a corn-snake skull, but the photography’s not very good.
Finally, here is my snake, mouth open, showing the pterygoid teeth on the roof of the mouth:
What next? It seems clear that bugging is the only realistic way to free up the skeleton, and this may be the specimen that persuades me to invest in a proper colony of dermestids rather than just relying on whatever inverts happen to wander past.
It might be worth trying to skin and gut the snake first. Gutting will be easy; skinning might be very difficult. I think that removing the skin from the skull without damaging the very delicate bones might be impossible. Can dermestids cope with snake skin?
I’m taking advice!
Sauropod Vertebra Picture of the Week 
December 18, 2014 at 1:24 pm
I would skin the body, but leave the skin on the skull. It should eventually fall off on its own, provided it is not attached to a full skin. I also recommend staking it down. My snake skeleton consists of a bazillion ribs and vertebrae with a bunch of isolated skull bones in a pile because the skeleton completely fell apart. Since I failed to straighten the snake or secure it, all the bones became completely mixed. On the other hand, it is one heck of a jigsaw puzzle…
December 18, 2014 at 1:46 pm
1) “It might be worth trying to skin and gut the snake first.”
Yes. You don’t want to leave the guts hanging around, especially if you want to go with dermestids. The last thing you want are maggots and so on that might create an environment that causes damage to the skeleton.
2) “Gutting will be easy; skinning might be very difficult.”
It really isn’t — but I agree that leaving the skin on the skull might be a good way to ensure things stay on a little longer (but also why miss out on the opportunity to examine a snake’s jaw muscles in detail when you have a perfectly fine example!?). However, you can definitely skin the skull without damaging the skull – the scales are not attached directly to the skull as in some other reptiles.
3) “Can dermestids cope with snake skin?”
They would probably eat the skin layer underneath and you may or may not end up with holes in the specimen. That’s been my experience with small lizards and fish if I didn’t skin them.
4) “How do you sex a snake?”
Look for the vent. If it is a male, you could also puff up the hemipenes with air or fluid.
Some good references on snake skulls and jaw muscles
Haas (1973) in the Biology of the Reptilia, vol 4? and Cundall and Irish (2008) in vol 22… which incidentally has now been made free online – http://carlgans.org/table-contents/ Wait – I thought publishers shouldn’t want to cut themselves from potential revenue streams on out of print books they don’t even sell anymore!? ;-)
David Cundall has published numerous papers on colubrid skulls which would all be great references to you for comparison. Personally, if I had a chance at getting at the anatomy of a snake head that wasn’t a victim of roadkill, I’d take it! :)
Also, if you plan to gut it with the kids around or they’re interested in anatomy, don’t miss out on the asymmetry of the lungs, etc. You might want to take the time in general to see what kinds of fun observations can be made if you’ve never dissected a snake before.
December 18, 2014 at 2:00 pm
How do you sex a snake, you ask? The most frequently used technique is to probe the cloaca and search for hemipenes (as you know, there is one on each side). Not fun to do on a specimen that’s been dead for a while though. The shape and length of the tail and shape of the scales around the cloaca can also help in some snake species, including Corn snakes (males have longer, slightly fatter tails). Use google for tutorials! Your specimen looks to me like a male.
December 18, 2014 at 3:07 pm
Many thanks, Nick, lots of good stuff there.
December 18, 2014 at 3:14 pm
Please document your experience with dermestids. I have held off on setting up a colony, but it might be the time to start one.
December 18, 2014 at 3:50 pm
You may also use a combination of chemical and mechanical preparation – carefully removing the soft tissues “manually” and clearing the skull with 0.2% potassium hydroxide (KOH) [for about 24 hours]. That is the procedure that I used when I was preparing lacertid skulls but some of my colleagues used it to prepare snake skulls (but mostly boids and pythons).
December 18, 2014 at 10:19 pm
This is definitely one for the dermestids, since it’ll be easier to keep all the ribs in order. I’d avoid nature-cleaning since any flesh that mummifies before being fully cleaned could be very hard to remove from such a delicate skeleton, and there’s a high chance of pieces going missing.
Maceration in warm water would work well, and would probably be done in less than two weeks if you skinned and gutted, and it’ll give you a head start on degreasing. Keeping those ribs in order will be a huge nightmare, though, if you’re not prepared. I’ve heard of people using a scalpel to separate their snakes into sections, each of which contains a few vertebrae and the associated ribs, and then macerating each section in its own container. That way there are far fewer options for vertebrae-rib associations to reconstruct.
December 20, 2014 at 5:33 pm
Can dermestids deal with skin? – the ‘derm’ in the name should be a clue. They like stuff that’s too dry for maggots, but not excessively so.
If the head dries out unskinned, the skin can be very hard to separate later from the skull roof, and you’re likely to get damage to premaxilla and nasals, and possibly prefrontals and dentaries.
Maceration in water means losing most or all of the connective tissue at sutures as well as joints, which is fine if you want completely clean bones but won’t add up to the information content of an articulated skeleton.
Most of the snake skeletons (or just skulls) I’ve prepared were from specimens in alcohol, usually formalin fixed, so insects were not an option and skinning was usually very easy. The skin’s not as tight to the skull roof bones as in many lizards, but I would always be interested in saving the head skin anyway. Starting from the lips can give you the whole skin with every scale intact, but getting it off the face cleanly takes practice; starting from a midventral incision (even a quite short one) and working up and out can also produce a good result (necrosis aside).
A few specimens I’ve dealt with had been skinned fresh and then packed in salt, where freezing or liquid preservative was not available; the meat comes off the bones very cleanly, but the sutures tend to separate very easily also.
NaOH is fine but I’ve used hypochlorite bleach a lot for small specimens; diluted, with or without a bit of detergent, in short bursts followed by a soak in water. Muscles come off very nicely when they’re the consistency of jelly, while you can leave just enough connective tissue to prevent disarticulation. I don’t see any progressive deterioration of bone once the treatment’s finished with a final soak and several changes of water, but I know it’s inappropriate for for big dense bones (not the best way to clean whale skulls, apparently). Careful not to overdo the bleach or you get bone erosion, disarticulation and irreversible decrappitude.
December 20, 2014 at 6:05 pm
Oh btw, the Skulls Unlimited pic looks like it might be Pituophis, and should be a pretty good guide to the Pantherophis skull (except Pit. has a more specialised, reinforced snout i.e. expanded & tightly bound nasals and premaxilla).
December 21, 2014 at 3:09 pm
Lots of really useful stuff here — thanks, John!
December 23, 2014 at 7:39 pm
As a total rookie I had no problem skinning a couple of gopher snakes, however I kept the head on the skin and just doused it in my preservative mix. 10 years later they still look great and even the (shriveled) eyes are still visible. For sexing, my herpetologist neighbor held the body on both sides of the vent, gently bent the body towards the spine to expose the vent, then pushed to evert the hemi-penes. These were fairly freshly dead, so I’m not sure this would work on a previously frozen snake.
March 5, 2015 at 9:51 am
How sick is someone to leave that poor snake to suffer like that????? Hate people like that!!!!
March 5, 2015 at 10:16 am
Andrea, I’m not sure what you’re suggesting. That the snake’s owner should have killed it outright rather than giving it the opportunity to recover from its injuries?