Dan, I don't think they are "very" different, but there's enough differences to make me curious and research the influences on the snakes that do affect some differences. I haven't had the opportunity to work with the Keys Ratsnakes, yet, but do know they are from an almost tropical environment, which has to affect their behavior. They also are smaller in length and girth than the standard corns. Color is somewhat different too, in that they have reduced colors, almost hypomelanistic I've heard, and reduced pattern. I think they are a little better climbers.
The Brazos Island Ratsnake, P. g. meahllmorum, is one I've been working with for a few years. Not a true island form as they are also along the coast in extreme s. Texas, near Brownsville, and on some islands, and down into Mexico, but never-the-less, influenced by the remoteness and coastal climate. Being at the southern extreme of the species we indeed see some differences in color, pattern, body shape, size, etc. They tend to be different shades of brown, the blotches are not round or square shaped, more h-shaped, the head is somewhat elongate, snout pointed more, there are less blotches, and there is an incomplete head pattern, and there is very little ventral pattern. They tend to be smaller, barely getting 40 inches, a little thinner, and almost entirely nocturnal.
Look at these couple pics and see what you think...


I do like exploring islands and noticing the affects islands have on animals (just got back from Hawaii, btw), but haven't had much luck getting corns and rats from islands. I did land a pair of corns this summer that are a cross bt. Miami x Keys corns and look forward to working with them. Later....
TC
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Ratsnake Haven: Calico and albino Chinese stripe-tailed ratsnakes, Mandarin ratsnakes, Chinese twin-spotted ratsnakes, South Korean Dione's ratsnake, Great Plains ratsnakes and corns 