Hi



Not all the snakes are venomous, just all the advanced snakes. Venom evolved one time, right at the base of the advanced snake tree (Colubroidea superfamily). The primative snakes (pythons, boas, sunbeam snakes, blind snakes etc.) don't have the venom gland. Also, the common ancestor of the narrow clade in North America made up of Lampropeltis/Panterophis/Pituophis and close relatives underwent a secondary loss of the venom gland and reverted back to the more primative constricting condition. The Asian ratsnakes however are venomous as are American garter snakes. Its only that closely related N. American group that has lost the venom (that we've documented so far, there may be other groups just like two unrelated lineages of sea snakes are independently becoming non-venomous due to their specialised diet of fish eggs).



This is not to say the venomous rat snakes are dangerous, they are not. Like the vast majority of the colubrid snakes, they produce enough venom to help settle down a frog but enough to harm a human. I keep making this point crystal clear so that there aren't any assinine laws put in place by moronic legislators! There is a remarkable difference between being technically venomous and being dangerously venomous.



Cheers

Bryan
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Dr. Bryan Grieg Fry

Deputy Director

Australian Venom Research Unit

University of Melbourne



www.venomdoc.com

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