Question about scale counts...

[jbuncc]

Well, I suppose it's a pretty basic question...

How do you do them? Do you basically take the shed skin, slit it up the middle of the ventral scales, spread it out, and count? I think I remember hearing that you count at the ninth, tenth, and eleventh saddle. I also think I remember hearing that you start at the very middle of the body, and count in a "V" shape towards the tail. Is this correct? What other scales other than the dorsal/lateral and ventral scales should I be counting (ocular, etc...)? And with the ventral scales, do I stop counting at the cloaca, or continue until the end of the tail?

Also, do you recommend using a pen or something to mark every 10th scale or so in case I lose count? If so, what works best?

Thank you for any help you can provide!
JB

 

[Seamus Haley]

I've never actually tried it with a shed skin, generally I've done them on live animals while someone holds it still (and with a magnifying glass quite often, my eyes aren't very good). If the shed is clean and intact though, it should work for body rows.

I think you're already aware that you can count literally every scale on a snake's body but... The only time it really becomes needed is when you're trying to make a subspecific determination, since doing this requires knowing what the scale counts are to start, and specific mention is usually made of the ones that differ between the designations in question, there's not usually much of a need to do a count of more than a few scale groupings. Since you mentioned saddles, I suspect you're talking about Boa constrictor ssp. the entire complex is something of a mess, especially when looking at animals that are the result of lines that have been in captivity for awhile as many of those are subspecific crosses at some point in the ancestry.

At any rate, one of the better descriptions I've seen for how to go about counting scales, other than having someone show you in person, can be found in the Audubon field guide oddly enough. They use some slightly different terms, especially for a few of the head scales, than many other sources, but it has some clear diagrams and the slight differences in terminology and actual scalation of species with a finer scale pattern than the "typical colubrid head" used in the diagram are a simple matter to determine.

As a really brief rundown on the body scales, it's not the total number lengthwise from head to tail, it's the number from the extreme dorsal point (above the spine, center of the back) down to the edges of the ventral plates. They can be counted in a row diagonally and back or in a sort of zig-zag pattern straight down the side, the counts will result in the same number. Marking the scales after a certain point (every five or ten for instance) when performing the count isn't a bad idea (with a non-toxic substance of course) although I have never tried that either, usually just counting twice to ensure the result is the same.

I'm pretty sure posting the diagrams I mentioned on a public message board like this would violate copyright laws but if you would like me to scan them and send them via e-mail (along with a diagram that shows scale counts and patterning for Boa subspecies) I'd be more than willing to do so. Technically I suppose it's still a violation of copyright laws but the scale is much smaller and it can't come back on Rich if I do it privately so I'm willing.