Reptile & Amphibian Forums

Hello everyone,

I'm interested in the color/pattern variation of yellow rat snakes, particularly those individuals that hail from the Carolinas and Georgia.

While these northern locale animals definitely show integradation with black and gray subspecies, can anyone hypothesize which selective mechanisms retain the longitudinal striping and various hues of yellow?

If anyone has pics of these specimens, can they please post them?

Thanks in advance!

The more northern you go, the darker the Yellow Ratsnake becomes. In some studies this clinal accumulation in pigmentation has been interpreted as an adaptation to a cooler climate. So far I haven't seen any reports indicating that the striped pattern is retained by mechanisms other than isolation by distance.

Here are some locality photos of yellow rats from coastal SC and GA. Their background color and intensity of striping varies amongst these individuals.

Note the intense yellow of the labials from the St. Simons specimen.
http://www.uga.edu/srelherp/jd/jdweb/Herps/species/USsnakes/Elaobsqua.htm

Well, like you stated, specimens from a more northern locale further away from peninsular Florida, will have a greater tendency to have possible intergradation with others of the complex.

That's not to say they can't get fairly dark in Florida also though,....but as a general rule, they are a "cleaner" animal with more prominant stripes and the futher down the peninsula they are from the less influence the have from another source.

I have seen some average ones with brownish/wheat coloration throughout Florida, with some retaining the juvenile blotching as adults, and on the same token, have seen some mind-blowing vivid yellow individuals as well.

These are a couple pics of a nice example of "quadrivittata" I captured recently in Brevard County in Central Florida along the Atlantic coast.

best regards, ~Doug

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"Better to be silent and thought a fool, than to open mouth and remove any doubt!"

Thanks for the examples.

The GA localities interest me, particularly from the barrier islands. While the distance between the mainland and these islands does not exclude gene flow, I wonder if it affects coloration over time/competition for habitat and prey interspecifically?

Yes,....

All those factors you mentioned can very likely affect what any given population looks like, as well as idividuals within a given clutch having variation as well.

Keep in mind there's plenty of "Greenish" Ratsnake influence up that way, were the Black Rat overlaps!

best regards, ~Doug
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"Better to be silent and thought a fool, than to open mouth and remove any doubt!"

Greenish rat integrades are also interesting. What differentiates them from yellow rat snakes in the similar areas that they occupy? Is the the longitudinal striping, or other characteristics?

>>What differentiates them from yellow rat snakes in the similar areas that they occupy? Is the the longitudinal striping, or other characteristics?

Yellows typically prefer and occupy the coastal areas at the northern edges of their range and have the longitudinal striping. Even though they might be a "green" color they are still considered yellow rat snakes. Blotches in an adult would indicate an intergradient specimen. Here is a range map from the Davidson U. website:

Davidson rat snake page

Another good reference is Palmer and Braswell's Snakes of North Carolina book.

Of course you'll have some European heterophobes that will disagree with all this, but that's OK.

dg