I think they do have venom, but it's more like a irratation to human's, and also because they have no fangs, it is prbably transmitted through saliva. I have a wildcaught garter snake, and he sometimes gets a little nervous and still bites me, and i will get a itchy irratation where it bit me, the irratation will stay for about 30 mins to 2 hours. I would still like to see it proven out that they do have some sort of venom, by the way here is a long clip of my snapping turtle video
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