Reptile & Amphibian Forums

I'm always suprised when they come out nicely. This girl is really showing some nice colors.
I tend to use cardboard hides for growing animals... they're nice and snug, and easy to replace when outgrown. So, don't laugh! She loves her milkbones!

Also, I've heard from a few people that you can sex WDB's by counting the black rings on the tail, which sounds vaguely plausible. She would definately not enjoy probing so if there's any truth to this (or an alternate easier way) let me know!

I try to collect data from fresh DORs I encounter here in south Texas; I recorded number of tail rings on fewer than half of the specimens I have dissected (so there was no uncertainty about the sex).

Of the data on 16 specimens I have handy here on the computer, 11 were males, 5 females -- all from South Texas "brush country".

Males: range: 4-6
mean: 5.5
mode: 6

Females: range: 4-5
mean: 4.4
mode: 4

Two females had 5 tail rings, 3 males had 5 rings
One male had 4 rings

To me this character shows too much overlap to be of much use in definitely establishing the sex of an animal. When I have a captive that I absolutely can't sex visually, I usually wait for a shed and count the number of subcaudals; with atrox, this is much more reliable.

Tom Lott

Thanks for the info... I figured it wouldn't be that easy! How many subcaudals should I look for on a shed skin?

If you combine the counts from two of the seminal works on Crotalus [Gloyd (1940) and Klauber (1956)], you get the following:

Males: 19-32, mean: 25.7
Females: 16-26, mean 20.1

This appears to include a sizable overlap (19-26). However, these counts were made from specimens throughout the entire range of the species and include, I suspect, a number of clines and areas of localized geographic variation. If you consider a specific geographic area, the apparent overlap in counts should actually be less. For example: in 19 south Texas specimens for which I have subcaudal counts handy, there is no apparent overlap (although a larger sample would likely show some).

Males: 23-30, mean: 26.8 [n = 11]
Females: 18-22, mean: 20.9 [n = 8]

So, for south Texas one could apply the rule of thumb that a specimen with fewer than 23 subcaudals is probably female (probability increasing as the count goes lower), whereas one with 23 or more is probably a male (probability increasing as the count increases). Again, this is likely good only for south Texas. If you know where your specimen is from and you know the count ranges from that area, you can get very good results this way. Adult atrox from this area are pretty easily sexed visually, so I only use this strategy on neonates and small sub-adults.

Tom Lott

Onr of the more informative messages I've seen on the board in ages.... thank you.

Tom Townsend
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"Seek first to understand, then to be understood"

NP